CONCLUSION

Even if we perform great feats of innovation, hard times lie ahead and the impacts of climate change are unlikely to be fair.

History and geography matter. There are some places that are dealing with natural attributes and human legacies that will be almost impossible to address. (Bangladesh, for instance, will find it very hard to adapt to sea-level rise under the best circumstances; many auto-dependent American suburbs will likely experience economic distress as resource and energy costs rise; the U.S. desert Southwest will be extremely stressed by both anticipated heat waves and fossil fuel-dependent land uses and economies.) How temperate the local climate is likely to be, how stable the surrounding ecosystem services are likely to remain, how wise (or lucky) the region has been in growing energy-efficient cities, how rich the local people are, and how much strength and integrity their national governments have — all these factors will matter, undoubtedly.

But I’ve come to the conclusion that readiness to act matters more than any of these. Places that invest boldly in the next decades in ruggedizing their systems, growing civic resilience, and building up the local capacity for innovation, adaptation, and rapid cultural change — these are the places that will find themselves most prepared for the storms on the horizon.

Being a city-region ready to meet the future (whatever it looks like) is more important than being luckiest in location or wealthiest at the moment. Successful engagement with future turmoil will demand leadership, strong civic cultures, commitment to change, tough choices, and aggressive action on changing big systems. No city out there is moving fast enough yet, but some are beginning to show signs of understanding the scope, scale, and speed of the change demanded of them. Others look great now, but are changing only incrementally and slowly. There comes a point where lack of action means further incremental change can no longer keep up with exponential problems.

On the other side of the coin, being a city-region that’s deeply engaged with the work of readiness and ruggedization may give unexpected benefits. Climate adaptation and recovery is going to be one of the 21st century’s biggest industries. Places that invent affordable, effective methods and tools for meeting these challenges aren’t just helping themselves weather the storm, they’re also expanding the range of the possible and quite possibly finding another competitive advantage for their region’s economy.

Personally, I’d rather live in a city that’s moving fast to meet the future than one that started farther ahead, but is stuck and complacent, or simply unwilling to go beyond mere incremental change. If I became confident that any city was indeed poised to be the real global leader, I’d move there in a heartbeat and help any way I could.

I know I’m not alone. In fact, I suspect that a city that really pushed itself to the forefront of urban innovation (and had a clear commitment to further innovation ahead) would find itself a magnet for civic talent, technical genius, entrepreneurial savvy, and global investment. The edge a leading bright green city gains in the next 20 years could put it in a position of increasing prosperity for a century, even in the midst of hard and turbulent times. To prosper while genuinely doing good is something to which we all can proudly aspire.

The best-possible scenario would be one in which many cities hurl themselves into fierce competition to lead in a bright green urban boom. That competition is probably not only the key to creating cities that offer the best, most sustainably prosperous lives possible, but also the best answer we have to the planetary crisis we face. We need a race to carbon zero.

Thinking

To precipitate that race, though, we need first to change the way we think and talk about the climate crisis.

When thinking about climate change, many people quickly find themselves hooked on a sharp snag: Unlike almost every other problem we’re used to dealing with, climate is a matter of absolutes and limits. We’re used to describing our approaches to solutions in terms of relative degrees of improvement: Dropping a few pounds on a diet is better than not losing weight at all; learning some home repair skills is better than not learning at all; reducing childhood poverty by a bit is better not raising the prospects of any children. We’re used to thinking about problems where making things a little better is a success of sorts, or at least an indicator of good intentions.

But climate change is not a problem that responds to marginal improvements. Instead, it is all about the total amount of greenhouse gases in the atmosphere; it is their accumulation that hurls us towards catastrophe, and the degrees of danger associated with that accumulation are out of our control (and only recently within our understanding). Put another way, it doesn’t matter that we’re less polluting than we once were. It doesn’t matter how good we feel about these improvements. The only thing that matters is that aggregate concentration, that parts per million CO2 number.

Because of this, climate change places severe demands on us as intelligent, ethical people. The net elimination of our greenhouse gas emissions is the only sensible goal, and the only really debatable part of that goal is who zeroes-out when. Regardless of where responsibility lands, the goal remains the same — and absolute. Within the lifetimes of many of the people reading this little book, humanity will either bring its climate emissions down to a number in balance with the capacities of the planet (and have begun a worldwide effort to pull carbon out of the atmosphere) or face worsening, destabilizing disasters. Our choice is binary: carbon zero or climate chaos.

Therefore, the type of city I tried to outline here is no utopian ideal. It’s a foil meant for you to use to imagine your own strategy to face up to that stark choice. The changes we need to see demand imagination as a first step, because we lack the example of any city, anywhere, that provides prosperity sustainable enough to meet our challenges. Creating visions of carbon zero cities is therefore anything but an airy intellectual exercise, a design folly, a futures game. It is the first step in designing survival strategies for civilization.

Those visions will need to move quickly to implementation, of course, but without hard, sufficiently ambitious targets, climate planning in even green-minded North American cities quickly becomes an exercise in dressing up existing policies and plans as climate action, making marginal commitments to new efforts, and calling for bold action on time frames that lift the burden of urgent action from the shoulders of anyone now in political office. Unless the target is both defined in a comprehensive way (for instance, a consumption-based approach) and clear in its numbers (for instance, net zero emissions by 2030), it will never serve to force the kind of plans and policies carbon zero cities require. That may seem hard to imagine now, but that’s precisely why we need to begin with the work of imagination.

Such imaginative work must transcend the prescriptive, though. The possibilities of a world of carbon zero cities are just as hard for most people to envision as the plans, policies, technologies, and systems that will make those cities possible.

Almost everything we need to do to reduce urban emissions will provide most people with better cities than they have today, with a quality of life better than the one they currently enjoy. Done right, life will simply be better — measured by health, safety, security, prosperity, life experiences, and effective wealth-building — for most people in carbon zero cities. Indeed, the big open secret about urban climate action is not how bad things are — it is how good things can get.

While the struggle to build those cities is first and foremost a struggle of vision — we can’t build what we can’t imagine — it won’t be fought in make-believe places or involve theoretical people. It will happen in the real world, led by real people.

The city in which you’re reading this is a carbon zero city in the making. It just doesn’t know it yet. It needs your creativity and applied imagination to show it what it is; to show it its future.

– Seattle, June 2012

Sustenance: Bringing cities and nature together

Everything in the human world originates in nature: Everything around us is made of parts that are either mined or grown. Most of our attention, when it comes to climate, is on the mined — particularly on the effects of burning mined fossil fuels, like coal, oil, and gas. And these fossil-fuel emissions are by far the biggest danger we face, and so focusing on them makes sense.

Yet dirty energy is not the only source of greenhouse gases. Other climate emissions are created when we grow things. Still others arise from our management of ecosystems we more traditionally think of as wild. Unless we treat natural systems wisely, we won’t be able to reduce emissions to the levels we must; and ultimately, cities offer a lever for change that at first might seem counterintuitive. That’s because urban economies dictate how the natural world is turned into the human world, and whether that transformation becomes sustainable, or not.

Food and climate change

To discuss the ways cities and nature are linked — and why changing urbanites’ relationships with natural places could help lower a city’s carbon footprint — the best place to start is with food.

Feeding our cities is a less important source of greenhouse gases than transportation, building, and consumption; paradoxically, though, changing our food systems could offer profound reductions in emissions. That’s because, done right, agriculture, fishing, and forestry could change from being destructive practices to being vehicles for atmospheric restoration.

Most of the time, when the subject of food comes up in the context of climate change, consensus about the nature of the problem is hard to come by. Many people are simply unaware that what we eat has any climate impacts at all. Some dramatically overstate the importance of agriculture in a developed-world city’s climate emissions, claiming that one-fourth, one-third, or even one-half of all emissions come from agriculture (for U.S. cities the real portion of emissions coming from food systems seems to average around 13 percent). Others acknowledge that agriculture has impacts, but essentially believe that since we all have to eat, there’s little we can do. Only a few have more nuanced views.

Similarly, when solutions are brought up, hostile camps immediately emerge. Some focus on what we eat, insisting that dropping our consumption of animal products and overprocessed fast food is the only step to consider. (Eating less red meat and emphasizing lightly processed foods would definitely have a beneficial impact on our emissions. It would also certainly have real health benefits — and America’s obesity epidemic is more than just a human tragedy, it’s a climate problem, as we saw in chapter 3.) Others focus on where our food comes from, advocating locally grown food. Others look at the problem as centered on the food itself, and discuss ideas for reinventing food, such as developing lab-grown meat and genetically engineered algal proteins, establishing industrial aquaculture, and using smart-breeding programs to produce more efficient crops. Others, still, look at the nature of industrial agriculture, and the massive chemical and energy inputs it demands to produce food, and say the answer must start with a turn to smaller farms, fewer inputs, and better farming techniques.

All of these views are right. All of them also suffer from little-discussed limitations. And all of them, to my mind, overlook the most important fact about food: It is the by-product of ecosystems, and an intimate connection between our bodies and the workings of those ecosystems. To talk about food and climate is ultimately to speak of cities and nature, and how to bring them back together.

Farming and ecosystems

Essentially all the food we eat is created by natural systems, directly or indirectly. Even the most engineered, miles-wide agribusiness farm, growing one genetically altered variety of corn in vast fields, drenched in pesticides and fertilizers, worked by a few men and women in enormous machines — even that farm is nature. The crops on that farm grow in living soils built out of minerals, previous plant life, and an abundance of microorganisms. The planet’s water cycle produced the rains that water the furrows (even when that water is “fossil water” pumped from deep aquifers). Bees or other insects pollinated the plants. The sun provided the energy for photosynthesis, filtered by an ozone layer, which is itself a product of the oxygen plants release. The carbon cycle of the planet’s oceans and forests kept the weather generally stable. The genes in the corn itself came not just from breeding, but also from nature, part of the planet’s biodiversity. Even the most ruthlessly artificial landscape maintains its fertility only by drawing on nature’s bounty.

Bad farming can be described simply as farming that destroys more of that bounty than it gives back. Bad farming also tends to be climate-damaging farming. Some of the bad practices are matters of scale — the energy costs of working gigantic farms and far-flung distribution systems at a substantial profit; some are matters of trying to maintain monocultures and predictable crops in a world where both are gnawed on constantly by entropy; some are simply a matter of not caring very much about the future; many are the products of (and, in return, the generators of) the financial desperation of the farmers themselves.

There is a scientific term for the bounty of nature on which all farming depends: ecosystem services. And these ecosystem services are not minor matters. An international network of scientists estimated that the monetary value humans get from the ecosystem services that maintain civilization is at least $33 trillion a year. That’s 33,000 billions of dollars. But even that vast sum (equal to roughly half of the value created by entire human economy each year) is ridiculously low if we try to measure the replacement value of ecosystem services, because in many cases we simply don’t know how to replicate an essential service (say pollination) at any price. We don’t know how to remake the planet at will. We are, at best, gardeners: changing, choosing, working by necessity with a certain “watchful humility,” understanding that sometimes all we can do is nudge and encourage. We think we run the game, but all of our chemical expertise and engineering power only tilt the odds in our favor; they don’t change the rules. We still live off nature’s bounty, and bad farming erodes that bounty season after season.

Foodsheds

Better farming is the beginning of climate sanity. We know that it is possible to farm at more varied scales — with some old wisdom and new techniques, fewer chemical inputs, and greater embrace of more diverse crops and varied results — and produce better food with a lower carbon footprint. We also know that within the mad system of subsidies and unpaid externalities (externalities are costs a practice imposes on others) that dominates American agriculture, sustainable food costs more, while destructive food sells cheap.

The fast-growing local food movement includes many people who are willing to pay higher prices for food that reflects their values. Supporting good food wherever it’s grown is an excellent plan — for those who can afford the premium. The “local” part is a little trickier. Despite widespread discussion of “food miles,” the evidence seems to be pretty conclusive that the energy spent transporting food from distant farms is a small fraction of the total energy budget (and thus emissions) of that food. The difference in shipping something 1,000 miles and shipping it 100 miles is not profound; and that difference is often dwarfed many times over by the emissions a person generates if he or she drives to the store to buy that food.

Nonetheless, I think supporting local food is vital, for reasons that have nothing to do with how much diesel got burned trucking our lettuce to the supermarket, and everything to do with the quality of our “foodsheds” — the network of places from where our food comes. For most of us, our foodsheds are stretched across the planet to distant, little-known places we might not even be able to find on Google Maps. But we can also think of “local foodsheds.” Some people define these as all the farms and forests and fisheries and pastures within a set area, like a 100-mile radius, of wherever their products are currently shipped. But perhaps a more useful definition is: all the places that provide our food, which are also directly connected to the ecosystems that surround our cities — all the farms that drain into our local rivers, lakes, or bays (and the ones that drain into the watershed where we get our drinking water), for instance. Or, all the forests that help keep those waters flowing. Or, all the places that have a similar set of native species as the ones we might have found where we live. Different ways to slice it, all valid, and all pointing towards the same idea: We want the natural systems around us to grow healthier, and growing good food can be a way of nurturing that health.

Making our foodsheds healthy and resilient shows an engagement with long-term preparedness at its most basic. It would not be unwise for a metro region to have enough good farmers on enough good land in its region for it to feed itself (even if, in the foreseeable future, food systems are likely to remain global and trade-based). Explicit strategies to preserve farmland, create green belts, support farm families with good prices and farm capacities with good regional agricultural infrastructure (from processing plants to slaughterhouses) can lead to a region with a strong farm economy — and a deeply rugged regional food supply. This is important enough that cities ought to have people thinking about and working on food supply and city-country relationships, both within government and in the civic sphere.

We need a lot of market innovations for connecting people to surrounding ecosystems through foodsheds as well, but there are some great existing practices to build on. A strong market for sustainably grown produce can encourage farmers all over the region to invest in new, more sustainable practices. Steady support for small farmers (for example, through subscriptions to community-supported agriculture programs that connect us directly with a farmer) and farmland preservation can keep the farm belts around our cities growing crops rather than sprouting “McManors” (McMansions on what once were working farms). Supporting sustainable forestry at the lumber store, sustainable fibers at the clothing store, and sustainable fisheries at the market, can help reinforce good practices in forests, meadows, and rivers. Finally, supporting good policies — policies that reward good stewardship and punish ecosystem degradation — can help lower emissions.

How? There are a variety of farming practices that can reduce the greenhouse gases released in the growing of our food, from better tilling to “digesters” that turn animal waste into fertilizer while capturing the methane released in the process, which can then be burned as fuel. (Methane is a potent greenhouse gas, but comparatively harmless when burned.) Distribution practices can change — delivering food directly from farms to homes is much more energy-efficient than sending crops to distribution warehouses, shipping them to stores, and then having people drive to the store to buy them. Food waste can be reduced and food processing made less energy-intensive (or even less necessary).

Green infrastructure

Better practices on the farm only reweave one part of a region’s ecological tapestry, though. To really make a difference, we need to weave the whole working landscape together with wild systems, nurturing a healthier, hybrid ecosystem. A properly cared-for ecosystem grows more capable of buffering us against climate extremes as it heals. It also offers the potential of soaking up carbon dioxide already in the air as it matures. Foodsheds are our windows into that integration of human and wild. In places with relatively healthy and intact foodsheds, much is possible.

That includes the potential of weaving cities themselves back into the natural tapestry. Nature doesn’t stop at the city limits, after all. Our cities themselves are natural systems (though, admittedly, of a strange kind), and those natural systems can be designed to minimize the ecological impacts of our lives.

One approach: building “green infrastructure.” Green infrastructure usually refers to urban systems designed to treat waste flows (usually storm water, wastewater, or organic waste) and turn them into something useful by running them through systems that mimic natural processes. Sometimes these systems look natural — many integrate greenery into their operation with plants and trees and mosses everywhere — but they don’t have to. What is ultimately most important is not the leaves above but the systems below.

District-level green infrastructure systems can also appeal to our innate sense of biophilia by surrounding us with life. Enough street trees planted to soak up rainwater and shade sidewalks in summer create over time an urban forest, adding a sense of leafy quiet to dense neighborhoods and giving us the wonderful feeling of walking in green cathedrals of old trees, while the view from apartment windows becomes dappled light and leaves. The air smells cleaner. Swales and rain gardens and collecting ponds reconnect us to water and the seasons. (If we get bold enough about combining green infrastructure with stricter water pollution laws, even some of our most-polluted urban rivers, lakes, and bays can actually become swimmable and fishable again within a few decades. Think about what it says that they’re not.) Small vegetable gardens give us a place to put our hands in the dirt and experience the satisfaction of eating food we’ve grown, and perhaps returning our compost directly to the soil again, feeling the whole cycle of food and life. Living in compact communities woven through with trees and gardens and running water gives us the chance to feel connected with natural flows even when we’re a long way from any wilderness.

But wait a minute, you might think. How can we have both density and green space in the same city? And, if you took the current allocation of urban land for granted, you’d be right to ask: In most cities right now density and green space are locked in a zero-sum game, and most of the time in a carbon zero city, density has to win.

Why would we take anything like that for granted, though, when our cities are home to vast acreages of extra land? I’m referring, of course, to the asphalt.

Roads and parking lots make up a gigantic portion of the surface area of most North American cities. For instance, though no official figure exists, planners I asked estimate that 40 percent or more of Seattle’s total area is roads, parking spaces, and auto-oriented infrastructure — and that’s likely on the low side of the national average. In even the densest North American cities, thousands of acres are covered with parking lots and parking spaces; thousands more are taken up by roads that are likely not the highest, best use of the public land they occupy.

If we succeed in the kind of “mode-shift” I discussed in the Urbanism chapter — if larger numbers of people choose walkable neighborhoods that are well served by transit and either use their cars less or give them up completely — we could reclaim many sparsely used roads for better uses. Some streets we might convert wholesale. Some we might want to shave a lane or two off of. Some major streets will always be in heavy demand, of course, and will need to be maintained well for heavy use. Most cities will find, though, that they have a large pavement surplus, if they’re brave enough to use it. (In fact, not only will most cities find they have a pavement surplus in the future, most already do now.)

We can afford to plow up the pavement. The money is there in budgets currently spent maintaining and upgrading roads. Some green infrastructure, thoughtfully designed, fits perfectly the needs of pedestrians, bicyclists, and transit-riders, so newly designed streets can often meet the needs of both storm water and strollers. Though I don’t know of any comprehensive studies on the subject, I’d think the smart bet is that green infrastructure and pedestrian- and transit-focused streets are significantly cheaper to maintain than a comparable amount of large-scale infrastructure and roadway would be. What is certain, though, is that people like to live in lush, green neighborhoods. Homes shaded by large trees or facing parks routinely command higher prices than houses surrounded only by lawn, asphalt, and concrete.

Cities and soil

Discussing biological waste demands a certain amount of discretion. While most of us are happy to hear about the composting of yard waste and food scraps, many of us get uncomfortable when we discuss industrial biological waste, and downright squeamish when the subject turns to human waste.

The fact is, though, that all biological waste is soil, temporarily transformed. And we now have more ability than ever to complete the transformation again, turning waste back into soil. Various biodigesters, industrial composters, and other systems exist to do the job, and with the rapid spread of cheap biosensors, health and safety is much less an issue than it was when our ancestors started deploying the old systems we now use (many of our systems date back a hundred years or more; some have their deepest roots in Roman engineering).

Those old systems practically demand innovation. Though early pioneers have done amazing work proving the feasibility of some new approaches to managing organic wastes, there is no doubt that plenty of room for improvement awaits. This is true for the engineering of the systems themselves, the biology of the life within and around them, the design that makes them part of the urban landscape, the policies that regulate them, and even the financing that builds them — opportunities for innovation, right across the board.

One critical task, best, in my opinion, begun close to home, is repurposing our waste as a resource for regional ecosystem restoration. Every year, a large city sends thousands of tons of food scraps and yard waste to the landfill; treats rivers of sewage with toxic chemicals, straining and dumping the solids in waste deposits (or burning them in a giant incinerator, or just leaving the “clean” sludge to flow into a nearby body of water); and carts off massive amounts of construction and demolition waste. These waste streams represent vast flows of organic nutrients, biomass, and potential “clean fill” (stuff that can be used to fill holes, raise hills, and create dikes and levees).

Everything that flows into our cities that is not a toxic chemical ought to be reclaimed and used to promote regional health. Unfortunately, much of it is mixed with toxic chemicals along the way, or treated in ways that make it less useful or more dangerous. Sewage solids, for instance: Though people have used human manure as fertilizer for millennia, and we know how to handle it safely, our poo these days is often mixed with all manner of pharmaceuticals, household chemicals, and other nasty stuff. That limits its use to places where people and fragile ecosystems won’t be exposed to the dangers it poses, or where the ecological benefits of using the nutrients simply outweigh the risks. Putting these nutrients to use often just makes good ecological sense, especially when we consider that most of our storage and treatment options today actually release all the same toxics back into our ecosystem anyway — just in unplanned and haphazard ways (like the massive releases of nitrogen that are creating ocean dead zones at the outflows of most of our rivers). If we work carefully, we gain a gigantic source of fertile soil.

It’s hard for many of us to grasp how much opportunity there is in most places to restore soils, and thus ecosystems. The last 100 years have seen massive clear-cutting of forests, abandonment of farms, erosion of soils, poisoning of streams and lakes, and just general mayhem across the landscape. Much of North America is neglected at best. Quite a bit of it is in a state of slow collapse and growing vulnerability to the stresses and storms of shifting climates. Millions of acres that look green from the window of a jet flying 30,000 feet above ought to be in the ecological equivalent of intensive care.

We’d like to think that no such places exist, that every piece of countryside is too precious and pristine to fertilize with mildly toxic poo, but that’s just not the reality. Scattered all through our rural areas we can find devastated landscapes: polluted soils and dead lakes; once-fertile farmlands that have been scrapped and paved and built over with now-abandoned subdivisions and parking lots; hillsides where over-cutting of trees or strip-mining or careless farming has washed away the soil, until all that remains is a scrub of weeds on a rocky desert. These are all places that need profound interventions. They are not places that will recover if just left alone (at least not in human time-scales). They demand restoration on a scale we might almost consider terraforming (the creation of Earth-like environments where they do not now exist).

City systems that work more like nature promise, perhaps, the restoration of the parts of the natural tapestry that are most worn and torn. It is quite possibly within our capacities today to plant poisoned landscapes with bioremediating shrubs and trees that will gradually accumulate the toxins and heavy metals in the soil and water, concentrating them so they can be safely stored (or possibly reused in future industry, should the needed processes become available). Fertilizing a forest of such detoxifying plants with “biosolids” (human fertilizer) may well be a huge improvement in ecosystem health. Likewise, denuded slopes could be reforested, native plant nurseries created, and biomass farms (like bamboo plantations) fed. It seems to me we must find ways of doing this in which the risk is far outweighed by the ability to restore larger flows to health in the extremely rapid time frames in which we must act. Of course, seen in this light, using completely safe resources — like composted kitchen scraps as farm fertilizer — is a no-brainer. Our most problematic wastes demand we think more carefully, discovering new ways of working with nature, or simply ending the production of those wastes if they are simply irredeemable. Within decades we’ll need to stop washing those wastes away, because on a finite planet, there is no “away.” We live wallowing in the poisons and pollution we create.

By restoring the tapestry of natural systems, and reconnecting urban nutrients with natural cycles, we also gain a powerful way of balancing some of the harm we’ve already done: carbon sequestration. Forests and other healthy ecosystems contain vast amounts of carbon dioxide “locked up” in tree trunks, plants, and soils. Climate scientist Jim Hansen estimates that 20 percent of greenhouse gases now in the atmosphere come from centuries of deforestation (which, unfortunately, is at a crescendo today, with enormous tracts of rainforest being cleared and burned). But to a large degree, that process is reversible. We can plant forests (or engage in “afforestation”) and as those trees grow, they will lock up carbon dioxide currently in the air.

How much carbon could we take out of the atmosphere? In a 2011 paper, Hansen and his coauthors estimated that reforestation might offer the possibility of sequestering as much as 100 gigatons of atmospheric CO2 this century (that’s a lot). This ability to pull carbon dioxide we’ve already emitted out of the air by recreating the millions of acres of forests that covered the earth at the beginning of the last century is the best reason we have to believe that we can come back down to 350 ppm after we peak our emissions. Regrow Earth’s forests, and we can run the “carbon meter” backwards to a certain extent.

Those new “carbon forests” can also help fill in the gaps in the natural tapestry, making the systems around them stronger and more resilient. Indeed, restoring damaged lands around critical wild lands can help buffer those wild places from the disruptions we know climate chaos is causing. And, as these new forests mature, we can even imagine expertise in the craft of feraculture (the gardening of wilderness) emerging quickly (though none too soon).

So replanting the world’s woods is a pressing global task, and every region ought to be thinking about how to restore as many forests as it can within ecological sense and economic realities. Indeed, business models for afforestation that locks CO2 into tree trunks, provides ecosystem services, and supports threatened biodiversity, present maybe the most glaring unfilled solution space in North America.

But tree-planting is not the only way to pull carbon out of the atmosphere. It looks like fast-growing woody weeds will work, too. The reason? Biochar. If we grow and harvest those shrubs, we can char them so we can get energy from them (usually as “gasified” biofuels) while most of their carbon is kept bound in the charred leftovers. If we then dig that charcoal back into the soil, it enriches that soil while sequestering the CO2 (potentially for centuries, if done right). This raises the possibility that completely devastated landscapes around our cities could be transformed from wastelands to sequestration farms, fertilized with biosolids, creating energy and improving soils year after year while reducing emissions. Over time, these places could actually grow back into thriving forests. Our great-great-grandchildren might never know that these areas were once just barrens and patches of grass crowding up through old cracked asphalt and abandoned subdivisions.

If we both grew serious about our efforts to use metro waste to restore and reclaim our region’s hardest hit lands, and invested in good farming throughout our cities’ foodsheds, we could help change rural lands from carbon sources to carbon sinks. In the process, we might help struggling rural economies find new futures for themselves. We could see success all around.

But rural restoration and good farming aren’t magic. There’s no way the emissions reductions they offer could offset an entire city that went along unchanged. But that said, it looks entirely within the realm of possibility that a city could collaborate with its surrounding region in efforts that offset some or all of the emissions it might still release after it densifies into people-focused communities, rebuilds its buildings to be super-efficient, establishes district solutions for energy and water, and redesigns its consumption along 21st-century lines. Better relationships with nature will never offer us a free pass to continue with business as usual; however, they could help us close the gaps left even after we achieve major cuts in energy use.

Restoration as ruggedization

Finally, taking responsibility for our regional ecosystems can help us meet another critical task: that of ruggedizing our cities to withstand chaos.

For whatever else the century ahead of us brings, it will certainly bring all manner of chaos. Climate change we have already set in motion is producing strange weather shifts, extreme droughts and flooding rains, large storms and surging seas. (Un)natural disasters can interrupt the flow of goods (like the unrelated Japanese nuclear crisis did for electronics components), lead to crop failures and food shortages (as happened two years ago when Russia, after the worst heat waves and wildfires in its history, banned the export of grain), and provoke conflict and unrest (as has happened already in numerous countries where resources are depleting, like Haiti and Rwanda). Epidemic diseases will spread. Global systems upon which we depend will strain under the weight. And all of these stresses will come more frequently, somewhat unpredictably, and often unfairly.

Even in prosperous countries, it may not be prudent to expect the kind of disaster and recovery aid we’re used to thinking of being available. Especially when an entire region is hit with a serious problem — say, a megaquake jolts the entire West Coast of the U.S., or wildfires run out of control the length of the Rockies, or torrential rains flood cities and towns all along the Mississippi, or one of the super-hurricanes some scientists are warning of brings havoc to the Gulf Coast — there won’t be sufficient resources and capacities for the federal government to help everyone who needs it, or to restore everything back to the way it was once the crisis ends. And if we end up with large-scale disasters following one after another, we may well end up needing to look after ourselves. In those cases, the cavalry ain’t coming.

Furthermore, disasters cause emissions. We tend not to think of things this way, but every time something is destroyed and then replaced before it needed to be (or where it might not have needed to be replaced at all), greenhouse gases are pointlessly emitted. Not to mention the emissions caused by wildfires and the like. Large, frequent disasters mean lots of pointless emissions. Avoiding disaster, then, is an emissions-reduction strategy.

All of this means we need to focus on two critical goals: survivability and ruggedization.

Survivability means safety and security and the capacity to be productive and proactive, even in times of crisis. Survivability for cities is enhanced by systems that are less vulnerable and more resilient in the face of chaos. It is reinforced by the reduction of base demands, minimizing the inputs cities need in order to run. Put more simply, if your city can withstand some hard knocks and keep going even when supplies run short, you’re going to be much better off. If you live in a place that has put some thought into safety, security, and continuity in times of crisis, it then becomes reasonable to work with your neighbors and prepare your family to build robust survivability into your life. Its basic components are:

• Systems designed to prove less likely to break under strain. That might be because they’re networked systems of simple parts, like district energy systems; because they’re designed with a certain amount of redundancy and flexibility, like the Internet itself; or because they are within the direct control of the users (like local tool libraries), and therefore not as vulnerable to shortages caused by organizational breakdowns. Smart infrastructure and home systems designed to deliver optimized benefits for emissions reductions can often deliver survivability benefits, too.

• Patterns of living that don’t need a lot of resources to keep running. For instance, in an emergency, a Passivhaus building can be kept livable without central heat. Similarly, a neighborhood built for bicycling and walking can remain mobile even if fuel supplies are interrupted. Reducing a city’s vulnerability to resource disruption is a little-spoken-of but potentially major benefit of a carbon zero strategy, and can strongly reinforce community and individual efforts.

• As many citizens as possible possess control over life-and-death basics — they have a month or more of basic food supplies stored, they have emergency supplies like first-aid kits and flashlights, they have training in emergency responses — and at least a minimal level of emotional resilience built up through friendships and neighborly ties (so that people are ready to help each other, look out for the vulnerable, work together, and fend off problematic interlopers). Desperate people do terrible things. It is in everyone’s interest to avoid creating desperation.

Ruggedization is more important still. In a ruggedized city, the larger systems that keep a city operable do not fail even under extreme conditions. Ruggedization is the proactive avoidance of collapse.

The first condition of ruggedization is that vital systems are not placed in brittle contexts. You don’t want the city’s only aqueduct built in a place where it’s vulnerable to earthquakes, or its trauma center hospital built in a flood plain, or its emergency responders and police officers living far away when transportation systems could fail. Foreseeable disasters should be anticipated and avoided.

The second condition of ruggedization is that natural places and ecosystem services should be employed to make failures of vital systems less likely. Ecologists and engineers had been calling for the restoration of wetlands in the Mississippi Delta for almost 30 years before Hurricane Katrina hit New Orleans, and there is evidence that a healthier delta could have slowed storm surges and taken pressure off the levees protecting low-lying New Orleans neighborhoods, perhaps even preventing one of the nation’s worst “natural” disasters.

Restored ecosystems and ecosystem services can help prevent or reduce flooding and coastal storm surges, mitigate some of the effects of drought, lessen vulnerability to wildfires, resist onslaughts of invasive species, even prevent soil erosion and landslides. A city that wants to be tough in the face of disasters will be buffered by natural systems that are, themselves, rugged.

The third condition is that it breaks hard and repairs easy. Foresighted cities invest in the ruggedization of key systems, making them less likely to fail, even under absurdly difficult conditions. (This is especially true where the cost of even a single prolonged failure can easily outweigh the investment needed in ruggedization. For instance, having a 911 call center that becomes too hot to work in when a record heat wave hits will almost certainly cost more than building a better-designed call center in the first place.) Rugged cities also have the capacity to repair themselves: This runs from the most complex tasks, like quickly restoring safe water in a compromised urban system (by having emergency plans and workers trained to implement them, for example), to the simplest ones, like being able to provide critical replacement parts quickly and locally (by having strong distributed manufacturing capabilities, for instance).

The economic benefits of survivability

All this costs money, but funds invested in survivability and ruggedization can, potentially, pay themselves back many times over. It is important to remember that system failures are often incredibly costly; societal breakdowns caused by grim necessity and fear are economically ruinous. The economic losses suffered because of Katrina are certainly many times the cost that would have been required to restore the Mississippi Delta; and that restoration would have left us not with a still-wounded city and degraded surrounding nature, but with a thriving ecosystem.

Cities that begin to act now to ruggedize will reap economic benefits. For one thing, they’ll benefit by being more insurable than they would otherwise be. Reinsurance companies have already signaled that certain kinds of development in certain places will soon no longer be insurable at normal rates; and as costs mount from climate change and other planetary strains, business as usual will almost certainly become much more expensive to insure. Cities with many places and systems at risk may actually become effectively uninsurable.

That may not seem like a big deal, but remember that a local government’s ability to get low-cost credit to pay for the work it needs to do is tied directly to perceived risk, and that risk is measured in part by insurability. If the giant reinsurance companies say your town is poised on the edge of disaster, and refuse to back insurance there, businesses are likely to avoid it, some of the most mobile citizens will leave, and your town is in for some serious economic hard times.

On an even more somber note, ruggedized cities with survivable communities are far better positioned to thrive within prolonged megacrises. While I think betting on apocalyptic collapse is an unwise and perhaps unethical position to take, the facts are that some very serious, responsible institutions (like national militaries, scientific academies, reinsurance agencies, and intergovernmental financial bodies) warn that we are vulnerable to large-scale, widespread disruptions, potentially of extremely dire magnitudes.

It’s worth remembering that long, slow effects are often more difficult to mobilize against than sudden, dramatic catastrophes. With that said, smart cities should be preparing themselves for a variety of scenarios. That includes having at least thought through responses to climate-related disasters.

The absolutely wrong approach to take is trying to relocalize everything and imagine our small communities as fortresses of isolation in a landscape of chaos. Survivalism and separatism do not have good track records in history. Even in the worst-case scenarios, living in a dynamic and innovative city is a better survival strategy than any other that people of regular means have available to them (if you can afford a remote island, an extensive self-sufficiency setup, and a private army, that’s a different story).

Our goals ought to be to ruggedize our own cities and push as many of the wider political and economic systems in which we participate towards resilience and sustainability. Indeed, places that are pushing hard for change will, I believe, be the most prosperous places to be in good times, and the safest in bad times.

Read on: Conclusion: There’s still time if you act now

Addressing another danger — network security breaches — will demand not only more willpower, but also a shift in approach. With the increasing digitization of everything comes a corresponding increased risk in cyber-crime, complex system failures, and simple vandalism. That risk cannot, unfortunately, be met by not changing — our current systems present terrifying vulnerabilities — or by handing responsibility for the problem off to central authorities. The risk can only be met by three strong responses.

The first is open approaches to systems design that allow numerous users to understand those systems and find their weak spots and flaws; software evolved by these approaches has consistently proven more resilient than proprietary, purely commercial competitors, and Jamais Cascio and other leading technology futurists believe these open approaches can be applied across a vast range of systems with similar results.

The second is strong international laws and collaborating legal forces capable of finding and stopping lawbreakers like terrorists and organized criminal syndicates on an ongoing and successful basis. This, we should note, is much more about promoting the stability of fragile states and international rule of law than it is about high-tech espionage.

Third, we should understand when the controls and security systems we need demand people and human relationships, not more algorithms. We’ve for too long believed that every relationship can be commoditized and outsourced, and forgotten how critical community cohesion and learning actually are.

We tend to forget, too, how unsustainable our current technologies are. Right now, the entire technology sector is pretty much toxic, climate polluting, and materially unsustainable. Yet this is one area where I am actually fairly confident we can see major progress in the next decade, with breakthroughs in engineering, industrial processes, and product design. Some of the world’s smartest people are already at work on this challenge. They just need to work faster.

So, a city of networked systems is no panacea. Built carefully and democratically, however, the digitized city offers powerful new opportunities for emissions reductions.

Back to Carbon Zero, chapter 5
Back to Carbon Zero, full contents

Consumption: Sharing capacities to cut carbon

Very few individual consumer choices we make have much impact on our carbon footprints. A handful — the kind of home we live in, whether or not to own a car — have huge implications. Most, though, are almost meaningless … until we add them together.

Start adding those small consumer choices together and their impact grows. Indeed, those small choices we don’t think of, and the bigger choices we rarely think about, sum up to a lifetime of consumption and waste that produces a massive amount of pollution. That’s why consumer goods make up our third-largest source of greenhouse gas emissions. We cannot build carbon zero cities while overconsuming as we do.

When we do grasp the magnitude of our consumption emissions, our reaction is usually to decide we need to use less. If we use less, the thinking goes, we’ll waste less. This is a noble response, almost certainly true in our own lives, and generally true in our cities as a whole. The problem is, how to do it? How do we design our cities so we actually use less?

What we know does not work is to ask people to make different choices. Studies show that almost all of us simply lack the attention and willpower it takes to evaluate the options and choose the climate-friendliest product or service every time we want to buy something. To make matters worse, many times we buy things not because we actually want to own those things in particular, but because the systems we use are set up in such a way that buying or going without are the only options. Other things we buy because we’re told we need them and don’t have the right information to figure out on our own if that’s really true. Still others we consume because keeping them out of our lives is harder than getting them and throwing them out (this is true, for instance, with phone books in most cities). If we’re going to tackle our consumption-related climate emissions, we need to rethink this whole system, not just ask people to shop differently.

Surplus capacity

Is our consumption actually making us happier? And I don’t mean, does consumerism make us happier? (The answer’s pretty clear that in excess it doesn’t.) I mean, do the things we buy serve the needs we want them to? Does buying stuff work?

We don’t talk about it much, but most of us own a lot of stuff we rarely use. We buy stuff we think we want, and often end up using it once or twice, and then putting it away in a closet or an attic (or increasingly, a self-storage facility — the construction of rental storage units is a booming industry, even in these recessionary times). I would not be surprised at all if middle-class families in the developed world own 10 times more stuff, by volume, than middle-class families did in the 1950s.

And that’s just what we keep. Most of us throw away a surprising number of objects completely unused, not to mention all the stuff we toss while it’s still perfectly useful (giving rise to a burgeoning redistribution industry of thrift stores, online swaps, and “wastematching” services, which find users for things we no longer want). Even the stuff we keep, though, we rarely use to anything like its full capacity.

The example I love is the home power drill. Americans, in particular, are in love with their power drills, but millions and millions of power drills have been sold around the world. Apparently, the average home power drill is used somewhere between six and 20 minutes in its entire lifetime. The rest of the time, it sits quietly stored away, gathering dust. Most people buy their drills for reasons similar to the ones I bought mine, to do a task. I wanted to hang some pictures, so I needed to drill some holes in the wall. I had a job to do, and I didn’t have the tool I needed to do it. So I went out and bought a drill to make those holes, then found myself with a drill I’ve used only a few times since, perhaps for a total of 10 minutes.

Since my drill took lots of energy and materials to manufacture, to ship, to sell (and now to store), each of my 10 minutes of drilling has a big ecological impact. If we think of the total amount of ecological impact I created as one drill’s worth, each minute, we might say, took a tenth of a drill to provide. Yet what I wanted was the hole, not the drill. The climate impacts of owning a drill were, in my case, an unfortunate byproduct of what Victor Papanek would call bad hole-making choices.

A well-built power drill can, with proper care and maintenance, deliver thousands of hours of hole-drilling. When I own a drill and use it for 10 minutes total, I am letting all those thousands of hours of surplus drilling capacity go to waste; if I used them fully, each minute of my drilling would take a minuscule fraction of a drill’s worth of impact.

Of course, I just don’t have thousands of hours of drilling to do. I don’t even own enough stuff to drill that many holes. To drill for thousands of hours, I would need to become a menace to society, surreptitiously drilling other people’s stuff, perhaps working at night and leaving my neighborhood pockmarked with hundreds of thousands of mysterious holes. The idea’s absurd, of course. But the fact is, most cities likely have hundreds or even thousands of years worth of surplus drilling capacity lying around. If every drill already manufactured was used with perfect efficiency, we might not need to make another one until the 22nd century. The same is likely true for all manner of tools, from socket wrenches to lawnmowers, beer-brewing equipment to high-quality scanners. We float in an invisible sea of surplus capacity, and wasting that surplus is a major source of greenhouse gases.

The trick, then, revolves around matching that surplus capacity to people’s needs in ways that make practical sense. In the case of tools, a number of solutions are already at work in various cities. Neighborhood tool-lending websites are growing popular. Tool rental is becoming common, spreading even to some big-box stores. Tool libraries have sprung up in a number of communities, and most appear successful. It’s increasingly easy to make holes without needing to own a drill.

Technology will only make it easier. More and more objects can be fitted with sensors, enabling users to know their location and status. And when you know where things are, and whether or not they’re being used, it becomes much easier to share them. This is certainly the case with cars.

Car-sharing has been around for decades, but until the last few years, you had to be pretty dedicated to participate. Mostly, this was because of sheer inconvenience. You had to know in advance when you wanted the car, and write or call in to the service to request a car reservation. Late returns, maintenance issues, breakdowns, and the like had to be laboriously noted, communicated via writing and phone calls, then attended to, resulting in frequent “gaps in service,” meaning that sometimes, even when you had written in to make a reservation, your car wasn’t there when you arrived. None of this was because the participants were stupid (far from it), but rather because limited technology made it extremely difficult to share effectively.

Today, however, in many cities I can be walking down the street, decide I want to drive somewhere, take out my phone, find the nearest available car-share vehicle on a map, make a reservation, walk over, use a swipe card to unlock its doors, get in, and drive away. Some services will even let me drive that car anywhere I want in the city and park it there, eliminating even the need to return the vehicle. For many urban-dwellers, car-sharing proves easier than owning a car — with car-sharing, you don’t have to worry about buying the right car (indeed, you can have your choice of many kinds of cars), keeping up with maintenance or insurance, finding long-term parking, or selling your car when it gets old. It is certainly cheaper, and for someone like me, who lives in a walkable neighborhood and drives only rarely, it is dramatically cheaper.

Ecologically, this is a huge win. If many people share the same fleet of cars, the surplus capacity can be spread out, meaning far fewer cars will serve everyone’s needs, and more people can sell the cars they rarely use. Indeed, a pioneering study in London showed that for every car-share vehicle that became available, six people got rid of their cars. More recent studies suggest that in dense urban areas, as many as 20 people may dump their cars for every new shared car in the neighborhood. If those people drive rarely — if they use their cars the way I use my power drill — then the ecological footprint of every trip they make shrinks dramatically when they car-share (and more so if the shared cars are low-emissions vehicles).

The technical term for an arrangement like car-sharing is a “product-service system.” An object that once was a product owned exclusively by one person (a car) becomes a service used by a group of people (the right to drive any of a group of cars). We already use all sorts of product-service systems, though we don’t think of them that way: a health club turns gym equipment into a workout service; a library turns books into a reading service; even an elite university turns a group of learned scholars into an education service (college educations would be even more expensive if we all needed to hire our own full-time faculties in order to earn a degree).

Collaborative consumption and sharing

Product-service systems don’t need to be limited to one product. We’re seeing an explosion of peer-to-peer lending and rental services now. Some are “collaborative consumption” businesses that connect people who have surplus capacity to rent with people who need it, skimming a small fee off the top. Examples include NeighborGoods (which connects people with tools and other household goods, to borrow or rent) and GetAround (which connects people with opportunities to rent their neighbors’ cars). Other services are noncommercial, simply letting people share and trade informally, like CouchSurfing, which connects travelers with short-term places to stay. I predict we’ll see an explosion of these person-to-person systems in the next decade, as well as a more general cultural shift that makes it more acceptable to borrow and share casually among friends and neighbors. In many cases, people find that sharing introduces them to new friends and broadens their community: Some people join sharing networks mainly for their social aspects.

These sorts of systems face some challenges, though. One is that many of us are somewhat introverted and experience interactions with strangers as stressful, and in situations where we’re already under pressure (say, the whole family is coming over for Thanksgiving and a pipe has clogged), we may simply find it less stressful to get the tools we need in the quickest, least-interactive way possible: buying them. Another is that, even for the more extroverted among us, some interactions require us to place a large degree of trust in strangers. This may serve to restrict the kinds of things most people are willing to share to those things that are comparatively safe and of little value (it’s not a big deal for me to lend someone my drill; it’s a much bigger deal to let him stay in my home). Some peer-based services may end up suffering the fate of hitchhiking.

Though hitchhiking was once (and may still be) relatively safe, a small number of violent assaults have made it feel like a nonviable means of trip-sharing in the minds of almost all Americans. Sharing services could come to be seen as dangerous as well. One scandal involved a woman who rented out her apartment on the short-term rental site AirBnB and then (she said) essentially had her life upended when the renters trashed her apartment, stole her things, and violated her privacy. Even if such stories represent rare and unlikely events, they may put a serious crimp in the willingness of many people to participate in sharing systems.

This combination of social friction and fear of strangers may, I think, drive more and more of these product-service systems to become restricted to networks of verified members. For many people, having a corporate intermediary (whether for-profit or community-based) is worth the extra cost if it provides a layer of safety and privacy. Far from slowing the growth of sharing efforts, I think intermediated systems will actually throw the whole phenomenon into overdrive.

Opportunities abound here. As we begin to look at our cities through the lens of capacities, rather than ownership, we quickly see the panoply of existing surpluses and a variety of business models to turn those surpluses into services. Some already exist (car-sharing is booming); some are being explored now (everything from shared high-fashion wardrobes to shared workspaces); some remain untested. In every study I know of, these sharing services have been shown to reduce the ecological impacts of the shared products. The unused capacities floating in our cities represent huge opportunities for lowering the carbon footprints of our consumption, while growing thriving businesses and providing new jobs.

And the more compact and people-focused our cities, the better these systems work. After all, if we live in a sprawling city and discover that the nearest drill we can use is a half-hour drive away, we’re much less likely to find that a viable alternative than if we live in a compact walkshed and find that the nearest drill is a couple of blocks away, or that we’re within the delivery zone of a nearby tool library. And walkshed living adds an extra incentive to using product-service systems. Since our homes tend to be smaller, it costs us more hassle and money to store stuff we don’t use very often. Living in a 1,200-square-foot townhouse, for instance, we’re much less likely to think it makes sense to keep a whole workshop of tools just in case we might one day want to use them. The more compact your living space, and the denser and more connected your walkshed, and the more it makes sense to share, rent, and buy services instead of buying stuff.

Rethinking needs

It’s one thing to make something and then endeavor to use its capacities as efficiently as possible; it’s a brighter thing altogether to invent different ways of living so we don’t need the thing in the first place. Not making trumps using well.

To truly reduce our emissions we need to reimagine how things work, transforming the needs in our lives and filling them in new ways. Design can bundle capacities, eliminating the need for many objects. Nathan Shedroff likes to use the example of the iPhone, which has eliminated the need to carry separately a mobile phone, an audio player, a PDA, a camera, a map, a watch, and a host of other small objects (he reminds us that not long ago to look at a lot of images we had to use photo albums and slide viewers, for instance) by combining all those functions into one hand-held object. (Not that an iPhone is a perfect product: It is far from sustainably designed, built by workers in shocking conditions, and designed to be constantly obsolescent. But the same could be said for all the many products it replaced.)

Our cities are full of systems and things that made sense in an industrial era; they’re still around because they remain profitable, but they are far from the last word on how things can be done. The way we uses spaces is a telling example.

We are conditioned to think of an office as a discrete place with a variety of spaces (conference room, work areas) that demand their own support systems (like office equipment and receptionists). Thus, if we want to run a professional business, we’re led to believe, we need to rent a large office, buy a bunch of equipment, and hire enough support staff to make us look good, even if we don’t have enough work to keep them fully engaged. Such a setup is often abundant in surplus capacities, from the unused conference room to the idling copier to the receptionist playing solitaire, waiting for the phone to ring.

Increasingly, though, smart businesspeople are looking for ways to share those surplus capacities. They’re co-locating the offices of their businesses, for instance, finding it’s much easier (and cheaper) to work in spaces with flexible systems (like movable walls and adjustable lighting that can be “reprogrammed” to serve a number of needs, from offices to a lecture hall), while sharing the support services involved, from copy machines to custodial workers. In this way, 10 smaller, leaner companies may thrive where one larger, more “professional” company struggled. And because those surplus capacities came with ecological costs, sharing them reduces the carbon footprints of the businesses involved.

The explosion of social software coupon services also demonstrates how people are learning to recognize and manage surplus capacities. These services exist in large part because of the ability of small groups with networked services to find, package, and sell cheaply the surplus capacities of various businesses. Unsold skydiving trips, empty restaurant tables, unused yoga studios — all are essentially worthless to the businesses that have them. When a service makes it cheap to sell these surplus capacities for a small profit (and a large discount to the consumer), the businesses gain more customers, gather marketing momentum, and raise their potential for future profits at little to no cost. This often proves a good deal for everyone involved. I suspect we have only scratched the surface of businesses that arbitrage surplus capacity to make a profit, in part because I think we’re only beginning to grasp the true magnitude of surplus capacities in our cities, or the additional capacities waiting to be released by rethinking how we do things in the first place.

It’s not about the quality of the mousetrap. The world abounds in “better mousetrap” ideas, many of which are, as Thoreau quipped, “improved means to an unimproved end.” Many of our ways of doing things are legacies of an era when information was expensive, and materials, energy, and labor were cheap. We’ve seen the example of how much more wasteful (and expensive) it is to drive around looking for bargains, rather than going online, finding the best deal, and having it delivered. We’ve seen the example of smart grids storing surplus power while it’s cheap and using it when demand is high. We’ve seen the example of car-sharing, wherein easy access to information about nearby unused vehicles has transformed the experience of car ownership. All these, though, are mere harbingers of a larger trend.

People are already using old capacities in completely new ways. Take the “pop- up” business. A pop-up restaurant, for instance, involves a temporarily vacant space that a start-up kitchen rents for a limited time in order to make money feeding people good food on slim margins, build recognition, and grow a patron list. Take the “share front” retail model, where a group of craftspeople, artists, or other producers occupy an empty storefront and sell their work collaboratively, sharing operating costs to a point where small businesses can afford retail presence. For that matter, take the short-notice swap meets (public bartering without the bureaucracy), the rolling speakeasies (unregulated nightlife on the fly), or the popular fitness “boot camps” held in local parks. All of these require physical spaces that are sitting un- or under-utilized, the power of walkshed technologies to gather people quickly, and expertise in quick-starting projects; they use those assets to provide affordable services people want as an entry to business. And as they grow (or fade), jump and move about, merge with other efforts or evolve into new shapes, these businesses bring their customer networks with them, grow those networks, combine and magnify them. Because at the core of these “temporary” businesses is not a service in a space, but a set of human relationships. Having that set of relationships gives them the ability to leverage surplus spaces into profitable businesses … and lower their carbon footprints.

The number, complexity, and capacities of those relationships are exploding in urban cores these days. The trend shows no sign at all of slowing down, in large part because the two things driving it the hardest — new technologies and new urban perspectives — are both still on very powerful growth curves. New abilities generate new potentials, and we’re in the early days of a technological revolution at least as big as the industrial revolution. Add enough new abilities together, let them cross-pollinate and accelerate each other, and they generate new realms of possibility.

New technologies and adding new capacities

Our homes may be cluttered with screens and gadgets, but most North Americans have only partially digested the technological revolution of the last 20 years. We still don’t quite know what to do with the capacities we already have, how to manage the impacts of all this constant connectivity, or how to define our relationships with coworkers, friends, and extended family in a world of shifting boundaries and telescoping intimacies. Many of us are confused, uncertain, and a bit afraid. This is particularly true for those who formed their expectations about life before the rise of the internet.

We’ve only seen the swell on the horizon, though — the big wave has not yet arrived. Technology is still hurtling forward. Noted technologist Ray Kurzweil predicts that we’ll see a billion-fold increase in computation-per-dollar — we might think of this as meaning our machines will work a billion times faster but cost the same — in the next 25 years. Now, I tend to question some of Kurzweil’s other predictions, but even if he were, say, 99.9 percent wrong on this one, the result would still be a million-fold increase. Let’s go on to say that as things get more complex and jumbled they demand more processing power to deliver the same amount of perceived benefit. Let’s say it takes 1,000 times as much computation power: This would still mean computers in 25 years will be 1,000 times more powerful than they are today.

But even focusing on the computers betrays a 20th century way of thinking. What’s most powerful about technology in an urban environment isn’t the engineering sophistication of our digital tools as much as the new abilities they give us to smarten up the dumb physical stuff around us; gain insight through the data about how we use objects, systems, and spaces; and allow social relationships to find new uses for them. The ability to track, monitor, measure, collate, extrapolate, and so on and so forth, means we’re beginning to amass vast amounts of data about how things work, how people use them, what things are where in what relationship to each other and in what state. As both augmented reality and small tracking/monitoring chips become more powerful and cheaper, we’re gaining the ability to see our cities in ways no human beings ever have seen them before.

Smart urbanism

What can our new insights teach us? If we can reliably incorporate smart technologies into more objects and systems, then we will have many, many times the ability to work with that data to find new opportunities, fine-tune innovations, and model completely new ways to use our systems. And by “we” I don’t mean “a few geeks,” I mean average, reasonably educated, reasonably skilled people. In just a few years, neighborhood groups, small businesses, school clubs, and activists will have the ability to work with incredibly powerful models at real-life scales in real time. A deeply networked city can offer countless windows of insight we don’t currently possess.

Combined with a civic spirit and some design creativity, these insights can make visible the previously invisible. A lot of systems work in ways that are not in the public’s interest, that are wasteful of public resources, that privilege rich neighborhoods and powerful users over everyone else, or that simply set default behaviors in ways that channel money from citizens to private interests. (The last is particularly egregious. The litmus test is: If average people had the workings of the system patiently explained to them, would they find the default settings fair, or would they feel they’d been taken advantage of? Most people, I submit, would be deeply outraged by many of the systems they’re currently defaulted into, if they knew their full range of options.)

Networks should reveal their workings. Networked cities that are transparent can make possible better (and fairer) operations of existing systems. They can also launch another wave of urban systems innovation based on rethinking the flow of systems, constantly modifying and improving their operations, and automating routine tasks that previously seemed unmanageable. When computation is cheap and data is open, every part of a city can get smarter.

One example I quite like the idea of is networked rain barrels. Right now, Seattle (like many cities) has a problem with what are euphemistically referred to as “combined sewer overflows.” See, every time it rains too hard, and the storm sewers overflow into the wastewater systems, the flooding water ends up washing raw sewage into our nearby lakes and Elliott Bay. This is both an ecological harm and a human health risk. Some systems thinkers at Seattle Public Utilities, though, came up with an interesting proposal. Seattle is already a town where many people are using rain barrels and cisterns to harvest the rain that falls on their roofs for use in their gardens. If those barrels and cisterns are already full when a heavy rain falls, the excess runs off into the storm sewers, where it adds to the flooding problem. If they are empty, on the other hand, they fill up with that rainwater and flooding is alleviated. The problem is timing it so that every heavy rain encounters empty and waiting barrels and cisterns. Well, using the networked systems already being deployed throughout our city, we could wire all those cisterns and barrels with simple switches that would open and release their water on a certain signal from the utility. That way, when a major storm is coming, the city’s cisterns and barrels could release their water when it is safe to do so — before the rain starts falling — and be ready to absorb the new rainfall, keeping it out of the sewers. Given that it is a multibillion-dollar task to upgrade every storm sewer in the city, even subsidizing these networked rain barrels and cisterns would be cheaper (and, of course, this approach would lower water consumption to a certain degree).

This kind of smart urbanism allows us to take the old, physical, analog systems around us and make them work together in new ways. We don’t need to replace all the physical systems that make our cities possible if we can adapt them to create new capacities. Dumb things can be woven into smart systems, but those smart systems will change the nature of those dumb things.

Recombinant manufacturing

Key to reweaving the urban fabric is remaking the things within it. I say “remaking” rather than making, because we’ve already manufactured a lot of the stuff that will be lying around in 20 years, and when it’s too expensive to replace that stuff, we’ll need to figure out how to get it to work better. Huge volumes of objects in our lives will need to be upgraded, retrofitted, repaired, or reused in some way. Because many urban instantiations are particular, if not unique, reworking them is a job that takes attention and skill: In cities, almost every job’s a special order. There are no ubiquitous answers. Each task will need to be approached with new tools, skills, and ways of thinking. That demands a community of innovative re-makers.

The tools are already here. With the advent of cheap design software and personal manufacturing machines, we’re seeing a democratization of design itself. Previously, almost all professional-quality design was done for corporate clients or by corporate design departments. This one fact alone limited the field of design possibilities people would likely consider to the very narrow range of products company leaders were interested in exploring. Sure, there were student designers, lone geniuses, a handful of nonprofit design efforts, and rebellious start-ups, but the vast, overwhelming majority of designed things were designed with a corporate client in mind.

Now something else is happening: A culture of making is emerging. Many, many more people have access to the digital tools and the free instruction that allow them to create at home designs that only a few decades ago would have required entire departments of designers, engineers, draftsmen, prototype makers, and so on. With “open source” hardware designs, simple versions of many functional components of products are becoming freely available to incorporate into new inventions. With cheap fabrication equipment, making a working prototype is a comparatively trivial task. Even small-scale manufacturing is becoming in some cases a garage-workshop affair — printing and fabricating designs downloaded off the Net.

Our minds have not caught up to the implications of this, to put it mildly, but over the next decade or so we’re going to see a Cambrian explosion of designs and design thinking whipping up all sorts of new potentialities out of the ether. We’ll see the least of it where we’re wealthy and more worried about lawsuits than poor design (and the most of it in places where meeting basic needs is still a challenge), but even in the richest cities, “makers” will be rolling out a dizzying host of new answers to the problems of daily life, fresh off their laser cutters and 3D printers and into our lives.

While makers scatter their new solutions across our cities, “re-makers” will be hard at work transforming many of the objects already there. For, as mentioned, even while we reimagine the systems of our cities, many of the pieces of those systems will still be old, pieces for which we’ll need to find adaptive reuses. Rethought systems will be working with rebuilt components, in other words. Rebuilding those parts will demand a sense of the interrelationships between objects, and insight into the limits of how much each object can be hacked, tweaked, reshaped, and refitted. The result will be, I suspect, recombinant: We will seek new evolutions of old things, adapted into new purposes in changing systems. The making and remaking of such objects can be thought of as recombinant manufacturing.

Sustainable design, new delivery methods, product-service systems, mutual organizations, and permeable ownership all offer the potential of much lower consumption-related footprints for greater effective prosperity. Recombinant manufacturing brings the possibility of not only creating nearly carbon-neutral new things, but also integrating old things into new low-carbon systems.

The death of speed

When we talk about trade, the debate conventionally breaks down into two sides: one that believes trade will not only grow in volume but speed, and one that believes energy costs will slow trade to a trickle. Both may be mistaken. The most likely result, it seems to me, is that trade will both grow and slow.

Think of it as “the death of speed.” The amount of energy needed to move objects is a function of how much they weigh and how fast we want them to go. Heavy objects take a lot of energy to move, even slowly; all objects take a lot of energy to move very quickly. Therefore, moving heavy objects quickly is incredibly energy-intensive.

Our culture loves shipping heavy things fast over long distances. Think of weekend tropical vacations, overnight overseas package delivery, or fresh-cut flowers and wild fish flown in from across the world; but also, think about an entire economy locked into just-in-time production methods, low-inventory retail, and so on.

As energy prices rise, and we feel strong pressure to reduce transportation emissions, it will make less and less sense to ship heavy stuff far and fast. That doesn’t mean the skies will be completely emptied of jets, or the roads of tractor-trailers. It means flying will become more expensive, as will airfreight and even truck shipping. Things that don’t need to be moved fast won’t be; lower-speed and more efficient options will become more common. In fact, rising energy costs are unlikely to change the economics much for commodities that already travel slowly: With global growth, we’re likely to see a lot more slow shipping, not less.

According to the experts I’ve spoken with, it seems very likely we’ll see a strong continuation of the trend towards increased investment in freight rail and high-speed passenger rail projects; in energy-efficient marine shipping (including sail-assisted shipping, perhaps); and even perhaps in the resurrection of some old services like passenger ships. We almost certainly will see low-carbon fuels (the airports of the future may smell like burned olive oil) and electric engines powered by clean energy. All of this could mean a sharp drop in the emissions associated with global trade, as well as a change in its nature.

Localized production and repair could gain some unexpected boosts here, similar to the return of manufacturing to the developed world caused by some large corporations’ policies of “on-boarding” — requiring that suppliers be distributed geographically overseas and include some domestic production capacity so that if a major disturbance occurs, the whole supply chain won’t shut down (like we saw happen after the Japanese quake of 2011, which nearly brought some electronics production to a halt). Metro regions that develop versatile, distributed, clean manufacturing capacities (building on what they have now) could see the death of speed increase demand for their region’s goods.

Upskilling

Remaking our cities will demand hard work, lots of it, and one thing missing from many city climate plans is the workers. Fitting our cities together anew is going to demand an outburst of new abilities in workforces that most of American business has left behind. If cities want to change at the pace demanded both by global economics and planetary realities, they will have to intentionally “up-skill” their workforces.

Sure, some have focused on the “green jobs” that change is creating, which is all fine and good. But I think that focus blurs the larger picture: All of the skills it takes to keep a city running need to be upgraded. Every system we change, from pipes to wires to fleets of shared cars, demands first having workers who can build and maintain the new system.

Carbon zero cities can’t be built without respecting — and investing in — the workers who will build them. We’re talking about a massive practical education task, done with minimal resources, and starting in many cases from essentially no existing institutions or programs. Over the last 30 years the U.S. in particular (but, in general, most of the developed world) has underinvested in — or flat-out dismantled — the vocational schools, union apprenticeship programs, and other educational opportunities that for decades helped unskilled workers join the skilled trades and industries. Now, these programs will need to be reinvented nearly overnight to upskill tens of millions of workers.

I don’t know the answer to this problem, except that I suspect it will likely mirror the revolution currently unfolding in American higher education, where skyrocketing tuition costs, outdated instruction methods, and weak job markets have sparked an explosion of reform ideas and do-it-yourself entrepreneurs, who seek to replace the American university with something that more directly (and affordably) meets the needs of more students. I suspect cities that successfully involve their workforces in change will be highly experimental in educating those workforces.

Scenius, attention philanthropy, and incubation

The need for cities to upskill workers is matched by the need for cities to invest in new capabilities in the professions, business, and civic culture. “Economic development” in a carbon zero city means something very different than building convention centers, attracting tourists and offering tax breaks for business relocation. It means making the city a hub of new thinking.

New thinking itself gives a city a competitive advantage. Expanding local adaptive capacities — nurturing the ability of our cities’ public institutions, businesses, and communities to change quickly — is critical to climate action, but looms even larger when we begin to broaden our scope of concern beyond sustainability. Because ecological concerns, energy problems, and resource scarcities represent only part of the rising tide of change eating away at the beach on which our sense of the normal is built. We must force ourselves to remember that even without the planetary imperative to build a bright green society, the flow of technological innovation, the increased pace of competition due to globalization, and the released energies of billions more people finally able to think beyond the pressing needs of daily survival would likely wash away everything we’re used to thinking of as solid. But the massive challenge of global sustainability pushes those waters higher than ever: The next few decades are likely to be the economic equivalent of a 100-year storm.

The main force of that storm has not yet made shore. No generation in history has lived through the kind of transformations that the young today can expect ahead of them. Even the World Wars pale in comparison to the planet-wide shifts that are already rolling in, one after another, like breakers on a stormy sea. Like any gargantuan storm, this one will bring tragedy, and plenty of it. This will be most true in places that lack either the resources to adapt or the cultural strength to embrace radical change. They’ll get clobbered.

Most cities, though, can choose to invest in the infrastructure of thinking. All but the most gutted have at least some resources to commit. Investing in the ability to innovate would be an extremely smart thing for any of them to do. Even if the sustainability benefits of thriving local design, engineering, and technology cultures were nil — and I don’t for a minute believe that’s true — promoting better intellectual and cultural infrastructure for thinking about the future is an extremely intelligent basis for any city’s economic strategy.

When that infrastructure’s working right, we see bursts of innovation coming from three phenomena: incubation, attention philanthropy, and “scenius.”

Incubation involves the studied effort to grow useful institutional or entrepreneurial experiments. The mark of successful incubation programs is not making lots of money — that’s a byproduct. Instead, you can judge incubators by the number of interesting failures or “one-off” successes they spawn. Those are the things that truly expand a city’s sense of the possible.

Attention philanthropy is a big term for a simple act: telling people about the stuff you think is cool. These days, when so many ideas compete for our attention, promoting great efforts you know about personally is a form of direct investment. In thriving cities, smart people engage in near-constant attention philanthropy, drawing resources and energy to new ideas and projects from throughout the city.

Scenius happens when incubation and attention philanthropy come together in the presence of the right cultural moment. Scenius is Brian Eno’s term for “the intelligence and the intuition of a whole cultural scene. It is the communal form of the concept of the genius.” Almost always, the most creative, daring, inventive ideas come not from a lone genius working in isolation, but from a network of innovative people working in close proximity to each other — people who (as Kevin Kelly points out) value risk-taking work, quickly share new ideas, focus intensely on the products of the combination of those new ideas, and use successes to bring more energy into the scene. Almost always, scenius demands shared locations — places where very different people rub elbows and spark unexpected connections.

The potential for cities to provide the medium in which scenius multiplies can’t be calculated in normal terms. A Department of Scenius is probably a bad idea. But it is possible for people who love discussing ideas to find each other, to reach out to other communities of thinking people, get together and see what happens.

Systems storytelling

I once sat next to a Boeing engineer on a flight out of Seattle. He was a quiet guy, but we got to talking, and he started telling me about the kinds of innovation the aviation industry was seeing. Then he told me something remarkable. Nobody, he said, not one person anywhere, knows everything about all the working parts of a passenger jet. Many engineers know a great deal about specific systems. Other people know how to manage those engineers so that their systems fit together. But nobody could tell you exactly how every part works, how they all are made, and why they were made that way. A system too complex to be understood in its entirety works because of a shared purpose, good information flows, and trust. No one knows everything. The airplane flies anyway.

Civilization is like one of those planes. Nobody understands the whole thing.

Because we’re so unused to thinking in systems, and because so many of those systems operate largely outside our view, few of us even know the shape of the systems upon which our lives depend, much less all the other more complicated, abstract systems that extend outward from our cities to cover the globe to make up civilization. Yet it flies anyway.

The new urban culture of innovation is revealing to us the workings of systems in cities. It’s also revealing the workings of cities in those systems. We’re seeing that cities are not the streets and buildings found within a set of legal boundaries, but the agglomeration of all the systems that make life in those cities possible. Our cities and those systems are the same thing.

We are forced, in order to think well about the world, to engage in collaborative thinking across disciplines, fields, and places. We are forced to build models, construct working analogies, and learn to debate systems functions and probable outcomes.

The need to grapple with complexity and interconnectedness as we remake our cities demands more and more facility for telling stories about systems. We require elegance in apprehending complex truths combined with skill in turning models into narratives. We have to be able to share a vision of the kind of airplane we’re building, so to speak.

“Systems storytelling” is how urbanites will come to understand the process of building carbon zero cities. In fact, it’s an essential 21st century civic and journalistic skill: It may be the only thing that truly illuminates how people, in their daily roles as citizens, consumers, and community members, are integral to tackling our planetary crisis.

And, as we will see in the next chapter, the stories of our urban systems need to include nature. Western culture has drawn a line between nature and the city for 400 years. That line was always an illusion. Now, we can’t afford to be blind to the reality that urban systems and natural systems are completely intertwined. They are parts of the same metaphorical aircraft.

Read the sidebar to this chapter: Drawbacks of the digital city

Read on: Sustenance: Bringing cities and nature together

Shelter: working with nature to drop emissions

Once we’re thinking differently about our streets, we need to start thinking differently about our buildings as well. How we build has a major impact on our climate emissions. To see why, we need to look at buildings themselves.

Buildings offer us many things: a place we can feel at home, a status display, a means of expressing our personalities, a productive workspace, an investment tool. But above all else, our buildings offer us shelter.

Shelter from what? The power of nature. Every day, vast quantities of energy flow through our surroundings. The seasons, the daily rotation of the Earth, the tides, the forces of sun and wind and rain: These are energies far vaster than anything human beings create by burning things. Most of us have only known exposure to the real power of nature — frost-nipped fingers, sunstroke, the misery of trying to sleep in wet clothes in unrelenting rain — through the occasional recreational misadventure. But for most of humanity, through most of history, the elements were a constant and threatening force. Vulnerability to the flows of nature was the most fundamental fact of our ancestors’ lives.

Traditional builders knew and made use of these flows. They had to. Trap the heat from sunshine (with a south-facing window, for instance) and a space gets hot. Block that sunshine (with a high wall or a line of trees, for instance) and that space will cool down. Open a space to breezes, and it will feel cooler. Make that same space airtight, and it will feel warmer. And, obviously, rooms with openings to let in sunshine are brighter than windowless ones. By orienting a building to the sun’s path through the sky and making good use of trees, screens, and windows, the best pre-industrial buildings were often surprisingly comfortable, absorbing the warmth of direct sunlight in the winter and making use of cooling breezes and shade in the summer. You can find examples of this vernacular awareness of seasons and flows in pretty much every culture in the world.

That doesn’t mean that every building worked in perfect harmony with the seasons, or that every building used quality materials, or even that every building was built well. Few of us would tolerate the miserable cold, the overwhelming heat, the bad air, the bugs, and the general discomfort of the huts that many of our bygone relatives called home. It’s easy to forget just how hard life was for most people.

With the coming of the Industrial Revolution though, cheap coal, oil, gas, and the electricity they generated when burned in power plants transformed the way we thought about the places we lived. They didn’t necessarily lead to more sensible buildings, but they gave us the ability to turn even shabby buildings into comfortable ones — by burning things we made our own sun, wind, rivers, and ice.

We don’t tend to think of things this way, but every fan is an artificial wind, every light an artificial sun, every furnace a hidden fire, every refrigerator a domestic glacier, every tap a tamed river. Since with cheap energy we could run air conditioners, furnaces, and electric lights at low cost, it became both financially easier (and more stylishly modern) to ignore natural forces and build in new aesthetics that often completely ignored the outside world and provided artificially comfort-controlled environments with mechanical systems. In many cases, it was cheaper to use energy thoughtlessly than to spend time thinking about how to use less of it. Comfort came not from a building’s design, but from its thermostats and light switches.

The result? Tens of millions of buildings that are energy oblivious: so poorly insulated that without heat their inhabitants would freeze, full of windowless rooms requiring bright lights even on sunny days, or built with huge shadeless panes of glass that trap so much heat that they are unlivable without constant air-conditioning.

Today, building operations (heating, cooling, lighting, and so on) are one of the major sources of greenhouse gases. When you combine the emissions created by running all those furnaces, air conditioners, and light bulbs with the climate costs of building these structures and making the appliances in them, the result is that our buildings are second only to our transportation systems in their climate impacts. If we’re going to build carbon zero cities, we need to rethink not only the shapes of our buildings, but the way in which they connect to the world around them. We’re going to need to imagine a major upheaval in shelter systems.

Retrofitting

What can we do about all that energy use? Well, if we knew that our cities were unlikely to grow much, and so the buildings we had today were going to be more or less the buildings we’d have in 20 years, our strategy would be all about preserving what we have and retrofitting it to be as efficient as possible.

Almost all of us understand that a building can be made more energy efficient. Building owners can insulate and air-seal their structures. They can refit them with more efficient appliances and better lighting. They can install energy- and water-saving fixtures. Even very basic home-efficiency measures can drop energy use for heating and cooling in a leaky, uninsulated building by one-third or more.

Using that much less energy, in turn, can save enough money every month that the payback time for the initial cost is often quite reasonable (and will be increasingly reasonable as energy costs rise). The main barrier here is financing: It’s hard in the U.S. to get the money to make these changes in the first place.

That’s why even the most aggressive retrofitting programs in America involve upgrading only 1 percent or 2 percent of a city’s buildings each year. (Some European programs aim for more than 5 percent, which is much better; after all, the difference between refurbishing 5 percent of a group of buildings every year and 1 percent is the difference between having changed every building in 20 years, and needing a century to get that job done.) Various policies, financing support, and tax incentives can speed up the rate of change. Even in the best case, though, we’re going to have a lot of work on our hands to steadily improve our existing building stock, for years to come.

Buildings for carbon zero cities

If in 20 years older buildings were all we had, that would be the end of this chapter: “Retrofit as quickly as you can.” But for many, if not most, cities in North America, the opposite looks likely to be true. Our cities will not be defined by what we have now, but by what’s coming.

As we discussed last chapter, a combination of fast-rising populations, regional migration, and changing housing preferences will likely mean that in some places, as many as half of the buildings in 2030 will be new construction; in a few places, a large majority will be new. The coming urban building boom presents both threats and opportunities. Our climate goals could be threatened by continuing old practices as we build new cities. Most new buildings today are only somewhat energy and water efficient. If we don’t raise our standards, new construction will be no better. The threat is that we build a flood of new housing, workspaces, and shops that will soon need to be retrofitted themselves, adding to the already difficult task of bringing our cities up to date.

It’s vital that every time a new building is built, we expect it to meet the highest possible green building standards. There are already some excellent efforts pushing for better standards. The Architecture 2030 project, for example, seeks by 2030 to have every new building be carbon neutral, with gradually rising minimum efficiency requirements. It’s an excellent plan, but we can’t wait until 2030 to raise our standards for new development.

Northern Europe’s Passivhaus standard represents the kind of goal we could embrace — practical now and ambitious enough to serve our needs in the future. A city in which every new building was built to Passivhaus standards would be a city on its way to radically reducing the carbon footprint of its homes, offices, and shops.

The German word “Passivhaus” translates literally to “passive building.” Passivity in this case means sticking to two simple core principles: work with (not against) natural flows and use airtight insulation to keep warmth (or coolness) where you want it. There’s more to it than that, of course, but that’s the basic idea. Add to those simple principles the latest design, manufacturing, and materials advances (especially new superefficient window designs) and what you end up with are buildings that work in a different way than most of us would expect.

Anticipating sunshine and shadow can allow architects to use the heat of the sun to warm a building in the winter; they can then employ overhangs, canopies, and trees to shade the building and keep it cool in the summer. Digital design tools for properly orienting buildings to these flows of sunlight and shadow are widely available now.

Our buildings bleed warmth (and coolness); the physics of the world dictate that warm and cold things want to seek balance, so when we heat a building on a cold day (or cool it on a hot one), all of that heat is “pulled” from the house by the difference in temperatures inside and outside. Insulation slows down the process. A little insulation keeps a bit more of the heat inside a bit longer; better insulation a little longer than that. But when you superinsulate a building, the rate at which heat is lost slows so much that much smaller sources of heat can keep it warm. Insulate it thickly enough and make it airtight and even very small sources of heat — like that given off by a candle or the body warmth of a person — can make up for the tiny amount of heat the building loses, keeping it warm without constantly burning fossil fuels.

Passivhaus architects also think a lot about ventilation and insulation. Most Passivhaus buildings have operable windows, situated in a way to maximize the advantages of breezes on moderate days. All use heat-recovery ventilation systems that bring fresh air into the building without wasting the heat inside the house, moving the air but saving the warmth. Some have “heat pumps,” which make use of the cooler temperatures underground or from a nearby body of water to provide energy-efficient air-conditioning.

Such efficiency measures mean Passivhaus buildings stay warmer with very little actual heating (or cooler with little air-conditioning). The result can be a building that uses 90 percent less heating and cooling energy compared to a “conventional” new American home, but is more or less as comfortable (some people find the even temperatures of passive buildings take some getting used to).

That building can be cheaper, too. Large central-air systems and furnaces are expensive. Being able to do without them or use more economical, smaller versions (being able to “furnace dump”) can make the up-front cost of a passive home much lower, even competitive with “conventional” building, while dramatically lowering the occupants’ energy bills — lowering them so much, in fact, that Passivhaus structures all cost less than conventional ones over the life of the building. With more rational government incentives and building codes, meeting Passivhaus standards can even be cheaper up front (and then much cheaper over the long haul).

And here’s the kicker: There’s no downside. Energy used to heat, cool, or light a building serves no other purpose — it offers no other benefits — and nothing is lost by eliminating its use (except perhaps utility company profits). As long as a given efficiency measure pays for itself on a schedule that makes economic sense to the person paying for it, there is no reason whatsoever not to do it. And given the number of ways cities benefit from energy-efficient local homes and businesses, there’s every reason to try to make the economics work as well as possible. When the initial investments are paid off, the financial savings, after all, go straight back into residents’ pockets and the local economy.

Prefabricated buildings present the possibility of even greater savings. Using factory-built sections and on-site assembly, these buildings can potentially offer greater accuracies, more airtight surfaces, less construction waste. Prefab construction may also speed the uptake of specific components and materials, such as high-efficiency windows or the use of bamboo, that offer real sustainability benefits, but which builders have been slow to adopt. Modular construction and prefabrication need innovation, but the potential is very real.

Every time a new building goes up, we ought to be building to the highest currently practical standard. The opportunity costs of not doing so are too great. Every time a construction site opens, we have a chance to save a huge amount of energy for as long as the new building is standing, or to commit that building to wasting energy or undergoing a potentially costly retrofit in the future. Every time we build we have the choice to use the new structure and its systems to help improve the functioning of systems all around it — and we’ll come back to that — or to simply let another building be an additional burden on existing utilities and infrastructure. Every new building is a chance to turn things a little bit more in the right direction.

These new buildings don’t have to be expensive or elitist. I am particularly enamored of the 99K House competition, which asked architects to build a 1,400-square-foot, three-bedroom home, using sustainable materials, passive design approaches, and energy-efficient materials and techniques … for less than $99,000. I found the range of entries to be incredible, proof that plenty of room remains for creative application of cutting-edge green building principles, and that the result can be affordable and accessible.

New building types

If we want to really change things, we can reinvent not only how we build, but what we build. I don’t have space to do the subject justice here, but essentially all of our current housing and commercial spaces are architectural accretions: Their forms represent layer upon layer of historical building technologies, fashion trends, economic class identities, and accidents of practice. Though they are highly evolved to be what they are, what they are is not all we might want.

Indeed, most of us put very little thought into what we want from our homes and workplaces. And while certain general principles seem to hold true most of the time — for example, people like natural light — the range of possible expressions of those principles is wide and still largely untapped. We might, just as one example, see more types of “multi-family” housing built for groups of single adults (the most rapidly growing household type) who wish to live with some degree of common space and community feeling, while retaining privacy and independence.

Though political pressures against innovation are huge — everyone from NIMBY reactionaries to architecturally minded fans of “aesthetic cohesion” in neighborhoods will line up to hate a new type of building — some even stronger pressures are building towards an upheaval in architectural practice. This would be an excellent time for those with the ability and resources to encourage experimentation.

Historic buildings and bespoke innovation

Though it’s easier to build new buildings when we want to live in truly energy-efficient ways, older buildings, and historic buildings in particular, offer opportunities we shouldn’t overlook. Historic buildings can play a critical role in fast-changing communities.

Historic buildings offer community benefits outside their own energy use. Historic buildings can help an area with a lot of new development retain a distinct character and sense of place. They make the streetscape more attractive (especially since many historic buildings were originally designed to serve pedestrians). They also tend to raise property values nearby, helping to increase neighborhood prosperity. Finally, many old buildings are just beautiful.

With strong incentives, many older buildings can be retrofitted up to Passivhaus standards. Though it costs more money and effort than just insulating and weather-stripping, retrofitting older buildings can often drive the energy savings up near that 90 percent mark as well.

A complicating factor is that every historic building presents a unique situation. Each historic building has a specific history of use, change, damage, and remodels. Historic buildings have strange mixes of materials, hidden structures (and structural problems); they may be regulated in different ways than new construction. Smart solutions to the problems historic buildings face are by necessity one-offs — bespoke.

In this regard, heritage structures differ only in their extremes. The fact is cities are built of nothing but unique cases; every neighborhood, every site, every building differs in ways large and small. Though it’s easy to describe the general principles we want to apply in creating a landscape of low-emissions buildings, we must not, as Paul Saffo likes to caution us, mistake a clear view for a short distance. In reality, applying those principles will be a matter not of blanket fixes but of myriad custom-made solutions, applied with insight and creativity. We’ll need an army of boundary-pushing architects, designers, engineers, and builders to transform our cities building by building. We’ll also need a new understanding of what makes a building green, followed by an even bigger suite of tools for crafting custom responses to each green-building challenge.

People-focused places and green building

We’ve inherited a warped vision of what a green building looks like, especially in North America. Strong leadership displayed by green-building pioneers in the 1970s and ‘80s — many of whom were hippies and had a strong preference for independent lives and back-to-the-land lifestyles — has led many of us to associate green building with “living off the grid.” The “neighborhood sustainability” movements of the 1990s and 2000s, with their focus on transitional technologies and small-scale local action, left some of us thinking that green building is fundamentally a small-scale, grassroots project. Other prominent design trends (like the idea of “zero energy” homes, which through photoelectric panels or small wind turbines create as much power as they use) have convinced us that green building is, in fact, a matter of greening specific buildings one by one. Conversely, the last decade’s photos of large modernist single-family homes in forests or deserts or by ocean bluffs have given us the sense that green building is something for rich people’s summer homes and magazine-showcase houses; that it is expensive and exclusionary.

Now, I’m not interested in trashing any of these efforts. They got us as far as we’ve come, often in the face of active opposition and steep learning curves. Many of the structures born of these movements offer terrific illustrations of principles we’d all do well to learn more about — but they do not necessarily offer the best models of the practices we need to embrace. Fundamentally, that’s because they’re not genuinely urban.

Density is the foundation of all truly green buildings. Living urban lives within compact communities is what makes possible the shift from greener structures to truly low-carbon homes and workplaces.

How? Homes in compact communities tend to be smaller. Smaller homes take fewer resources to build and use less energy to live in comfortably. The shared walls of multi-unit buildings make them more efficient. Better-designed larger buildings can also take less work to maintain than a comparable number of stand-alone houses, which translates to lower emissions. People living car-free lives don’t need parking, either, meaning the buildings they live in don’t need parking structures. This can save $10,000–$30,000 in costs for each unit, and shave as much as 10 percent off the building’s carbon footprint. A study for the EPA found that multi-unit homes in compact communities used half the energy, on average, of large-lot suburban homes — without using any different materials, technologies, or designs.

Just as importantly, we live differently in more moderately sized city homes, as well. A home stocked with smaller appliances and less furniture has a smaller carbon footprint. People with less storage space think twice about purchases they’re about to make, and, trend-watchers say, tend to buy fewer things overall. (At least they do on average — some people pack small homes to the rafters!) The shared services in a compact neighborhood are more sustainable than multiple individual versions; for instance, a 500-building neighborhood with one large gym is more sustainable than 500 buildings with individual home gyms. We’ll come back to this different way of living — and the ecological implications of different patterns of consumption — in the next chapter. For now, it’s enough to note that density and green living work nicely together.

Density makes the systems connected to the buildings work better, too. The infrastructure serving each building works more efficiently when the homes and offices in those buildings are more modestly sized. The United Nations’ State of the World’s Cities report makes no bones about it: “The concentration of population and enterprises in urban areas greatly reduces the unit cost of piped water, sewers, drains, roads, electricity, garbage collection, transport, health care, and schools.” Green homes in compact communities make the existing infrastructure do more work, more efficiently. They can do something more, though: They can make it realistic to change the kind of infrastructure we use.

District systems

When communities densify quickly, they encounter an opportunity to upgrade the systems that serve them. In a low-density area, with few new homes, there’s little reason or financial justification for local governments to go to the huge expense and trouble of digging up existing pipes, wires, and sewers and replacing them with the latest alternatives. In some cases, replacing old systems in spread-out communities costs more energy and money than the financial and ecological benefits of the new system are worth. Upgrading sprawl is often not cost-effective.

But when an area is both compact and rapidly changing, that equation is tossed on its head. The density of the community means more people using the systems, and thus more users to pay for the cost of upgrades (and more efficiencies in operation, as I explained above). The amount of new construction, meanwhile, means that a certain amount of digging, repair, and infrastructure development is going to happen anyway, as a natural part of the construction process in a city. People-focused neighborhoods with a lot of new buildings give local governments and utilities the motive and the opportunity to innovate.

District solutions arm them with the means. District solutions are infrastructural improvements that work for a number of buildings in the same area, helping them all get better-performing infrastructure at the same time, without having to rebuild the entire city’s urban systems all at once to do it. Done right, they are relatively fast, cost-effective, and transformative.

Perhaps the classic example is district energy. A common and successful form of district energy is a local combined heat and power (CHP) system. CHP often involves producing electricity with a steam turbine (commonly by burning relatively eco-friendly biomass like wood pellets) to make electricity while capturing the extra “waste heat” thrown off in the process and using it to warm local buildings as well.

What is waste heat? We all encounter it on a regular basis. If you’ve ever driven a car and noticed the hood was hot after you got out, you’ve encountered it. Burning gasoline releases an enormous amount of concentrated energy, but internal combustion engines can only use so much of that energy in actually propelling the car — the rest simply heats up the engine. It serves no purpose (unless you’re one of those folks who likes to cook food wrapped in tinfoil on top of your engine while you drive). It is wasted heat. Waste heat is also what makes an incandescent light bulb hot. Waste heat is always a sign we could be doing better.

Capturing waste heat can provide warmth in an extremely efficient manner. Waste heat can even be stored, using underground liquid “heat sinks” and systems of pumps; these in turn can be linked together with geothermal systems that use the more constant temperatures underground to heat (or cool) the buildings above it.

District energy and smart grids

But heating and cooling are not the only services district systems can offer: They can also introduce intelligence and adaptive capacity into dumb infrastructure. Many of us probably know about “smart grids,” electrical systems that let energy flow both into and out of buildings, measured and controlled by computerized systems. We’ve probably all heard how smart grids can cut down on inefficiencies, and can help route around problems, making blackouts and crashes less likely.

But what we might not have thought about is how many possibilities smart systems offer at the local level. Let’s start with power production. Though it’s certainly possible to put up your own solar roof tiles or wind helix turbine or whatever, numerous problems persist. You may not live in a building that’s well sited to make use of these. You may not use power at the right times to make optimal use of the system. You may lack the money to buy adequate storage. Or, your regional utility may not buy the power you generate back at a rate that covers your installation and maintenance costs. A whole field of companies has sprung up, trying to solve the problems of home-energy systems, and lots of progress is being made; but the fact persists that single home systems hooked up to large utilities are not as easy, cost-effective, or efficient as they might be.

But take a number of homes, a number of local energy systems, and a smart grid, and you’ve got the pieces for quickly improving the local energy infrastructure. A number of supplies and a number of users makes syncing supplies and needs more efficient, and offers the ability to build energy storage at a larger scale and lower cost. If the cars that remain in the neighborhood are electric vehicles, their recharging stations and batteries can become part of that storage capacity. If appliances with jobs that can wait (like a dishwasher) are linked to the smart system, then demand management gets easier, since the appliance can be programmed to do a task (like start the wash cycle for the dishes) only when supply is high and demand is low. Finally, smart systems allow the users to monitor their electricity use directly, and people use things differently when they measure them.

My favorite example of the last point is the Prius Effect. The story goes that if you take two cars that are in every way identical, except that one of them has a mileage meter and the other does not, the car with the mileage meter will get better mileage. At first, this seems dubious: If the cars are the same, how could one get better mileage than the other? The answer is that as drivers note their mileage on the meters, they get a constant stream of feedback on their driving. They notice that when they floor it as the light turns green, driving fast and braking to a stop, their mileage drops; it rises again when they accelerate more gradually, drive a bit more slowly, and brake less frequently. In effect, the car teaches them how to be better drivers.

This same kind of metering effect holds true in all sorts of systems. Feedback makes us smarter. For instance, multiple studies have shown that home energy use drops when energy meters are brought into the home and put in a prominent place, even when no other actions are taken. And we’re not talking about a minuscule drop, either — the reductions in energy use range in studies from 7 percent to 12 percent. Comparing usage between different people or households has an even stronger effect. Several projects have shown that when high-volume users are shown that their energy or water consumption is higher than their neighborhood average, they become more willing to invest in energy- and water-saving improvements, and may become more conscious of their behavioral choices.

More visible information may also make clear just how much energy we can save without in any way impacting the quality of our lives. Consuming less energy will not make us poorer. Huge amounts of power are wasted every day — we generate that power, move it, and consume it, yet it does absolutely no good for us at all. Squeezing the energy waste out of our communities — and this is a matter of systemic design to eliminate stupid, repetitive waste, not choosing to shiver in the dark; it is an engineering problem more than a behavioral one — would make a modest yet meaningful dent in our buildings’ carbon footprints just by itself. Better yet, it would free up money and time for more important things. All those efficiencies mean savings, and those savings add up quickly.

At larger neighborhood scales, these systems can be even more cost-effective, particularly when the local governments expedite work to avoid costly delays, and neighborhood businesses and residents purchase products and services together in order to leverage the best deals. Communities can encourage cultural collaboration and experimentation of a kind and intensity that society as a whole can’t match. A whole neighborhood of people who were excited to go “net zero” might find themselves happily taking steps that might feel onerous if they were acting on their own; they might, for example, be more likely to slim down to an electric car, buy more-efficient appliances, and be a bit more competitive about turning off unneeded lights. These steps, in turn, could make the whole smart system work better and more effectively.

The electric car angle is worth noting. We must change cities so few people need to drive (see the section on electric cars in chapter 3). That said, smart grids offer us an even stronger incentive to see the cars that remain converted quickly to electric vehicles. Electric cars are essentially battery packs on wheels, and since most cars, even in auto-dependent suburbs, stay parked in one of a few places for more than 20 hours a day, having a lot of electric cars means having a lot of batteries plugged into the grid. Since charging stations are programmable, cars can easily be fully charged when they will be needed, but store and feed energy back into the grid when they’re not. This means that the “peak load” of power usage can be met in part by stored-up energy created at other times, a very useful thing when dealing with renewable energy sources that are intermittently available. (We don’t want to buy EVs just for their batteries, though. Simply building more storage capacity into local systems is a better economic and ecological bet than buying electric cars to fill that role.)

What’s true for energy systems is also true for water. “Smart pipes” is a buzzword for various monitoring and measuring systems designed to do for our water use what smart grids do for our energy use. Many water-saving measures (like low-flow showerheads) are already available, of course. Adding smart-pipe systems allows the demand for water to be handled more intelligently. Why talk about water at all in a climate discussion? Because water is energy intensive: It takes energy to capture water, to store it, to pump and purify it, to deliver it to homes and businesses, and to treat the resulting wastewater. And since every one of those steps can be done in more intelligent ways, and every part of these systems can incorporate a variety of water supplies, alternate water uses, and ways of treating wastewater (as we’ll see later), smart pipes might mean a leap in water conservation.

Innovation zones

We have tons of design and technology innovations left to discover in every one of these fields, both in principle and practice. We need to learn a lot about applied innovation in an urban context, and we need to learn it quickly. We need experimentation, risk-taking, new approaches, and just plain creative weirdness. Most of all, we need permission to fail.

And there’s the rub. Most cities have elaborate codes, accreted case by case over decades, designed specifically to avoid failures, almost at all costs. Now, overall, most of the original intentions behind these codes were unimpeachable. Bureaucrats compiled them to protect citizens from known hazards and unscrupulous landlords, contractors, and developers. They compiled them because people sickened or died, were cheated or injured by the practices the codes are designed to prevent. Many of them remain in force for two reasons: First of all, the inherent dynamics of government make it far more likely that someone will be inspired or pressured to add something to the code than to spend time eliminating unneeded parts of that same code. Secondly, property owners are inherently conservative about their property values and often believe that these codes protect those values; therefore, they view change as an economic threat. (Because they allow safely awful projects, codes in actual practice in most cities rarely protect anything of importance. If the average property owner realized what monstrosities are generally within the permitted range of most codes, they would rest less easy, but that’s a story for another time.)

So while these codes often sprang from a desire to protect the public, many of these same codes are out of date. Many are full of contradictions; many are needlessly inflexible. Anyone who’s been around sustainable urbanism for a while can tell you stories of great projects, projects everyone — the neighbors, the builders, the banks, the bureaucrats, everyone — likes getting wrapped up, mummy-like, in red tape. In timid, corrupt, or conservative local governments, code is often actively used to discourage and delay innovative projects, for any of a variety of reasons. Even in communities with forward-looking and well-run local governments, innovation in the built environment is often a matter of figuring out how to permit a practice despite the code. For some projects, these kinds of costly delays simply cut into the profit margin and disincentivize risk-taking; other projects are rendered financially untenable. The most interesting experiments are often the ones that are most entrepreneurial and novel, but these same projects are often the ones with the most tenuous financing. For these projects, red tape means death.

And yet it is precisely these kinds of projects that expand the range of possibilities in our cities, that bring new solutions into play, that help change the thinking of professionals throughout their whole fields. To lose scrappy, start-up attempts by architects, planners, engineers, and place-based businesspeople is to lose your edge. Without an ecosystem of small risk-takers expanding the boundaries of the possible, the projects bankers are willing to invest in will change very slowly, if at all. Successful examples make the best arguments.

One solution? Create specific, legally defined areas where codes and regulations are stripped to their minimums, and bold thinking is actively encouraged. Projects in these special innovation zones would need only prove that they avoid very basic hazards — public health risks, unsound structural engineering, toxic pollution, fire — and that they meet larger legal standards that the city is powerless to change (for instance, that no explosives are produced, all appropriate professionals are licensed, and that no racial discrimination is practiced). Beyond that basic set of strictures, they would have the capacity to challenge constraints, try new things. They might even be able to experiment with financial models, looking to crowd-funding or microbanking, for instance.

Every city needs a place where innovators are encouraged to try new things and take chances, and at entrepreneur’s pace — not the normal glacial pace of bureaucratic process. Currently underutilized or abandoned areas can be turned over to small- and mid-scale experiments in carbon zero work, commerce, and living. Think of them as seedbeds for new urban ways of life. Such zones could quickly become hothouses for growing the kinds of urban innovation carbon zero cities need. If they bloom, they will certainly draw the kind of creative young people every city hankers for — what many of the brightest of the next generation want most of all is to participate in making a better future. Done right, these innovation zones could change the economy of their entire region, as well as greatly accelerate climate-friendly technologies, designs, and start-up businesses. The ability to create innovation zones might even prove a new advantage struggling cities have when competing with more prosperous ones.

But it’s not just buildings and infrastructure we need to reinvent. How we live within our cities also demands reexamination, and there, the possibilities prove even more unexpected, as we’ll see in the next chapter.

Read on: Consumption: Sharing capacities to cut carbon

Urbanism: Why good walksheds mean lower emissions

How we build our cities determines how we live in them.

If we are going to imagine a carbon zero city, in most cases we need to start with a fresh understanding of how we get around in them. Transportation, after all, generates the largest share of humanity’s greenhouse gas emissions. Cars account for most of that, but it’s not just driving cars that’s causing those emissions. Though the oil we burn driving is a catastrophic problem in its own right, those emissions are only part of the climate impacts of a huge set of systems that enables our driving. Factories and dealerships, roads and highways, parking lots and gas stations, road repairs and wrecking yards — put them all together, and these “automotive systems” represent the single biggest contributor to global climate change worldwide.

So, getting a 90 percent reduction in transportation emissions is a serious job no matter where we live. But it’s a giant task in many North American and Australian cities, where car ownership and use (and thus emissions) are far higher than in cities elsewhere, and where most planning decisions were made with car traffic foremost in mind.

One thing is clear: We can’t get to new possibilities with old thinking. Turning the ignition key and starting our car — no single act more defines the 20th century’s idea of prosperity, or offers a sharper contrast to the realities of the 21st century. Business-as-usual forecasts predict the world’s car fleets will double or even triple by mid-century. Car companies, with their old assumptions, see nothing but growth ahead. If their assumptions were right, there would be no way we could drop transportation emissions by the roughly 90 percent we seek.

Electric vehicles

What about electric cars, though? Can’t we just make all our cars electric and be done?

It’s true that an electric car charged with clean energy emits essentially no greenhouse gases while being driven. The big problem with electric vehicles is that they do nothing to counteract the large share of automotive-system emissions that don’t come out of the tailpipe. Running a car on electricity — or fairy dust, for that matter — won’t make the factory in which it is manufactured, the car dealership in which it is sold, the highways on which it drives, the mechanic’s shop in which it is serviced, the parking lots on which it sits, or the junkyard in which it dies, emit any less CO2.

Even beyond that, though, there seem to be sharp limits on the number of electric cars we can get on the road. Carmakers have been extremely resistant to manufacturing EVs. Even now, hybrids and electrics make up less than 1 percent of all vehicles on the road worldwide. And since it takes years to bring out a new car (from design to dealership) and more years (18 years, by the best estimate I could find) to replace even America’s fleet of cars (and in poorer countries, cars are kept on the road much longer), simply replacing every car in the world with electric vehicles is unlikely to happen in a reasonable time frame. Indeed, a recent Pike Research study found that even with a predicted increase of 4,500 percent in the number of EVs on the road by 2017, they will still only make up 3 percent of the global car fleet.

I wholeheartedly agree that pretty much all cars should be efficient electric vehicles. I also agree that electric cars are well-suited for cities, have advantages to offer as car-sharing vehicles, and can help provide storage capacity to a smart electrical grid — three points EV advocates make frequently and with good cause. We need to acknowledge, however, that the option of taking hundreds of millions of cars off the road by replacing them with electric vehicles in the next 20 years is not realistic. Better cars can be part of carbon zero cities, but we can’t just change the kind of cars we drive and leave everything else the same.

Not transportation, but urbanism

How then do we get that 90 percent reduction? By thinking in new ways that better fit the reality of our times.

Because we’re so dependent on our cars, when we think of improving transportation, we tend to think only of how to avoid traffic jams and speed cars along more quickly. This approach isn’t working on its own terms, leaving aside the demands of the climate crisis. Unfortunately, in a thriving city, when we fight traffic, we lose every time. We’ve spent more and more money on creating wider streets, building more bypasses and highways, but traffic itself hasn’t gotten better. In large part this is because of an effect called “latent demand.” In a growing, car-dependent city, many more people would already drive today if driving were more convenient; therefore, the minute we build a bigger highway, or widen an arterial through town, or eliminate stoplights on a busy street — increasing the capacity of those roads to carry traffic — more people start driving again. Sometimes you buy yourself a few years of reduced traffic, but even the most successful highway construction projects inexorably lead back to gridlock. You just can’t build your way out of a traffic jam, and when you try, you end up with packed streets, polluted air, and bankrupt local governments.

But the problem we need to solve isn’t traffic: It’s access. Transportation is all about access through mobility. We want easy access to our workplaces, to our kids’ schools, to the doctor’s office and hair salon, to the theater and the church, to the shops that carry the products we want, to the bars and restaurants where we meet our friends. In the second half of the 20th century, planners envisioned a world where access to all of the goods and services we needed would be provided by mobility — if we wanted something, we’d drive to get it. The result is the landscape we see today, especially in the suburbs, where millions of people take many trips a day in their cars just to keep up with their lives. With our communities arranged this way, there’s little choice but to drive. When we provide access through mobility, we grow ever more dependent on our cars.

Compact communities and access by proximity

We have another choice, though: access by proximity. Simply put, access by proximity means building neighborhoods where the things we want are nearby. Compact development — building neighborhoods that feature a mix of homes, businesses, and community amenities within easy walking distance of one another — brings the things we want closer to the places we live. The most climate-friendly trip is the one we never take in the first place, because what we want is already close. Compact development is the key to quickly converting as many climate-damaging car trips into climate-friendly trips-we-never-take. It prioritizes building better places, not busier roads.

Urban density reduces the number of trips residents take in their cars, and shortens the distance they drive for the remaining trips. It is possibly the best-documented fact of urban planning that the denser the neighborhood (all other things being equal), the less people drive, and the more their transportation emissions drop. If their neighborhoods are compact enough that many of their needs are within their “walkshed” (the area they feel is within a convenient stroll, roughly about a half a mile in every direction for most people, though a wider area for fit young adults), the amount of time they spend in their cars can drop dramatically.

How far can this go? How dense is too dense? We haven’t yet hit a point where the connection between denser neighborhoods and less driving breaks down. People drive less in New York than Los Angeles; they drive less in London than New York; they drive less still in Singapore than London. Certainly, the connection between density and low transportation emissions holds true at any level of urban density Americans are likely to see in the near future. If we want one simple guideline for reducing our car emissions, it’s this: Make our communities more compact. Density is destiny, when it comes to transportation.

That said, not everyone wants to live in cities as dense as Singapore. Luckily, we don’t have to in order to create big changes. Densities that are much lower, more akin to the way small towns were laid out before the car, can provide sufficient cohesion to change the way communities get around, while densities more like the core neighborhoods of San Francisco or Brooklyn can stir dramatic shifts.

Most of the time, transit isn’t practical at low densities. It only starts to become practical as enough people live within walking distance of a transit point, like a bus stop or light rail station, to make running a bus or train worthwhile. Once more people do live in a neighborhood, any increase in population makes things better: more neighbors just means demand for even better transit. This is part of the reason planners push to have the areas around stations built up in “transit-oriented development.” The more people who live near transit, the more practical transit becomes.

Compactness also makes transit work better. Planners have long noted a phenomenon they call “transit leverage.” Simply put, transit leverage means that people who ride transit some of the time tend to drive less the rest of the time. Every mile a transit rider goes on public transit results in between four and nine fewer driving miles (depending on the community). That seems strange — one mile of train travel, say, should only displace one mile of driving, since they’re both forms of transportation. In reality, though, urban transit travel is different: People usually walk or bike to and from transit stops, which means they tend to plan their trips a bit more carefully than drivers do, and as transit ridership grows on any particular route, more businesses and services locate along the route to serve those riders. This means that a person who, say, walks to the station and commutes by train to the office, may well go to the gym and grab a coffee on the way in, then shop for a gift, hit happy hour with some friends, and buy a few groceries on the way home. What would have taken someone in a car a number of trips, the transit rider achieves on a round-trip ticket.

Compact communities bring more destinations closer together; this alone promotes walking. While it is certainly possible to have unwalkable density (think office parks of towers surrounded by parking lots separated by busy roads), in general, having more people around means more pedestrians, slower traffic, and safer streets (crime drops precipitously when there are lots of people walking in an area). At the same time, having walkable streets helps people in a compact community gain more access to their neighborhoods. Compact communities and walkable streets are symbiotic.

People-focused streets and deep walkability

What makes a place walkable? It’s not complicated: good sidewalks, pleasant public spaces, street trees and benches, and so on. A number of excellent primers exist describing what makes a place more walkable. My favorite is Jan Gehl’s Cities for People. Gehl describes walkable, compact neighborhoods as “people focused,” which I think is exactly right, and about as elegant a description possible. If, when walking, you feel like the neighborhood is focused around your needs, then your community is doing it right. If you feel that the experience of walking is unpleasant, even dangerous, then your community is doing it wrong. Simple. (The same, in general, is true for biking, though sometimes the needs of bikers need to give way to the needs of people who are walking.)

The more people-focused neighborhoods a city has, the better those neighborhoods work. Walkable streets experience what we call “network effects.” Having the only telephone in the world would be pointless. Having one of 20 is better — you now have people to call. Having one of billions makes your phone into a universal form of communication. That’s a network effect.

The process obviously applies to transit: Living close to the only transit line in a city is better than nothing, but when you live near multiple lines going different places and connecting to a variety of other lines going still more places, then transit opens up the entire city to you. With good planning, transit can quickly become not only cheaper and greener than driving, but also faster and more effective. Driving across the city through traffic might mean you’re stuck in snarls for hours — while an express train hurtles by, delivering its passengers to a mesh of connecting services that can get them anywhere they need to go. When the network effects of transit kick in, they make possible something no individual transit line can accomplish.

Accumulating benefits works even more powerfully for walking. Living within one small walkable area is pleasant, but if that area is bounded by barriers like highways, unbridged rivers, developments with no thoroughfares, or just streets that feel unsafe and dangerous, that small walkable community begins to feel like an island, rather than a starting point. What cities need instead is something I call “deep walkability.”

Deep walkability describes a city in which a person can walk to almost any destination along great walking routes, a city in which walking is a viable means of getting from any one neighborhood to another, or even all the way across town. (The same, it might be said, applies to deep bikeability, though bicyclists can more easily share existing roads, even where no bike lanes exist. On the other hand, walking in the middle of the road is an excellent way to get killed.)

When compact communities function like nodes on networks of transit, bike lanes, and people-focused streets, they tip the balance of convenience away from cars. More walkable urban neighborhoods served by more ways of getting around: that’s the closest thing we have to a simple solution to climate change. A world in which most people called livable, walkable, transit-served, compact communities home would be a world well on its way to the deep reductions in transport emissions we need.

Rebuilding the suburbs

Driving through America’s suburbs, it can be hard to see all this walking, biking, and transit use happening there anytime in the future. Looks can be deceiving, though.

It’s important to remember, first of all, that “suburb” is pretty much a catch-all word that we use to mean “places that are not core cities, but not farmland, either.” That single term hides a huge diversity of places, from just-built pods of McMansions selling a taste of country life on the far urban fringe, to classic streetcar suburbs which can be difficult to tell apart from their neighboring city. When the discussion is about compact community and walkability, the term “suburb” is not a very useful one. More useful are the terms “inner ring” and “outer ring.”

The inner-ring suburbs are the first suburbs, built up into the 1960s and 1970s. Often they featured more modest family homes on smaller lots, and had streets with sidewalks and trees. Quite often, inner-ring suburbs grew up around an old small town main street or along commuter rail stops. The result is that the inner-ring already has a range of places, some of which already have a great neighborhood feel and people-focused streets. A fifth of all Americans call these inner-ring suburbs home (52 million people, according to a report by the Brookings Institute).

Big opportunities await these older suburbs. Because many inner-ring towns have “good bones” (they’re already compact and walkable, at least in places), they have something to build on. Because they’re close to central cities, they could be in high demand. With the right combination of new housing to raise densities, new investments in transit and walkability to make that density desirable and an emphasis on their existing strengths (parks, schools, historic buildings, and so on), many inner-ring suburbs could grow into places that have a people-focused, small-town feel. This would make them both much less auto-dependent and much more competitive in the regional housing markets.

It won’t be a simple task — on top of the obviously hard work of attracting new investment and building new systems, many older suburbs have huge fiscal challenges with declining tax bases, aging housing stock and infrastructure, and (in some places) increasing concentrations of low-income residents pushed out of the more expensive central cities; quite a few inner-ring suburbs have experienced sharp decline in the last 10 years — but retrofitting suburbia for walkability and compact community offers at least the opportunity for an economically competitive (and low-carbon) future.

It’s harder to be sanguine about the future of the outer-ring suburbs, especially the very fringe suburbs often called “exurbs.” Many of these suburbs are not only dependent on lots of driving, they were designed for it, top-to-bottom. In many cases, trying to walk their feeder roads and arterials falls somewhere between unpleasant and suicidal. Densities are too low to support realistic transit of any kind. The existing infrastructure, as crusading civil engineer Chuck Marohn points out, is unaffordable: These suburbs already don’t have the tax bases to maintain their spread-out roads and utilities and this problem will worsen as oil prices rise and the demographic shift towards cities continues. (Marohn calls the financing of suburban development over the last 30 years “a Ponzi scheme.”) Several million homes already sit vacant and unwanted in the exurbs; millions more may go unwanted in the near future. The outer-ring suburban model faces permanent foreclosure. Nothing the U.S. or Canadian federal governments can realistically do will save that model. It simply makes no sense. I fear that people who stay in the outer-ring suburbs (because, say, they’re under water on their mortgages and can’t afford to sell their homes) are going to find themselves in what become essentially sprawling ghettos, lived in mostly by those too poor to live anywhere else (this is already becoming the case in many places across the Sun Belt).

What brave outer-ring suburbs could do is try to save themselves by remaking their communities into something new. A smart suburb could bid to draw new growth, radically redraw its street plans, invite innovative small-scale redevelopment projects, lobby for transit service and think about how to shrink its infrastructure commitments to something fiscally sustainable … and it might work. I don’t know any outer-ring suburb that’s done that yet, but it seems possible, given sufficient motivation to chart a new course.

Healthier cities

Living in people-focused neighborhoods will also mean we live longer, healthier lives, on average.

We’re just beginning to get a real sense of how deeply connected illness and unsustainable living are, but it’s very clear that people in walkable, compact neighborhoods live longer (and live in better health) than suburbanites.

Density itself makes for safer streets — studies find that “a 1 percent increase in urban density translated into a 1.5 percent decrease in traffic deaths and a nearly 3.5 percent decrease in pedestrian fatalities” — but walkable density is even healthier. A recent study published in the American Journal of Preventative Medicine showed sidewalks were the main factor influencing physical activity, and that cross-culturally, people who live in a city neighborhood are twice as likely to be physically active than those living in the suburbs. In this light, the well-documented correlations between rates of obesity, diabetes, and heart disease and the amount of time a person spends driving are not surprising. Indeed, the health benefits of walking are so great that researcher Alan Durning found:

[W]alking 30 minutes a day, five days a week, adds 1.3–1.5 years to your life, on average. (More vigorous exercise adds even more.) On reasonable assumptions … this relationship means that for every minute you spend walking, you get three back. Time spent walking, then, is utterly free. It’s time you would have spent dead.

Less traffic in your neighborhood also makes you healthier. Fewer cars, driving more slowly, means you’re less likely to be hit and killed by a car (ending up as one of the more than 30,000 Americans who die from car collisions each year; not to mention the hundreds of thousands who are injured or the $99 billion in losses the Robert Wood Johnson Foundation estimates are caused by car crashes). Fewer cars means healthier local air as well, which is good since as many Americans die from the effects of air pollution as from breast cancer and prostate cancer combined — more than 70,000 a year.

“If doctors and other health experts designed our cities, they would look quite different than the sprawling communities we see today,” says Sonal R. Patel, MD, of the American Lung Association. “Cities would provide more healthy choices, more opportunities for walking and biking, better access to transit, less congestion, more housing close to workplaces, and more parks for kids and families to enjoy.”

Land use has a massive impact on our health and safety. It’s also clear that other changes we want to see in a sustainable community — from more access to healthy food to a broad shift away from toxic chemicals in manufacturing and household goods — have big health impacts. Though no one to my knowledge has yet done a comprehensive, holistic study of the health benefits of the transition to a carbon zero city, my suspicion is that those benefits will prove to be mutually reinforcing and profound.

This is good for us. It’s also good for the planet. Right now, health care as an industry is a major source of climate-changing pollution. Many of those emissions are spent treating people with chronic but preventable lifestyle illnesses. With a combination of much healthier citizens, more sustainable practices on the part of hospitals and insurance companies, and more closed-loop and low-carbon design principles incorporated into medical equipment and supplies, I find it pretty easy to imagine a carbon-zero health-care system. That alone would account for a non-trivial slice of the emissions cuts we need to make. Given what we know about the dire public health impacts of climate change, it seems to me that the health professions have a special duty to lead through their own practices.

The coming urban boom

I bet you’re wondering, how much can we actually change the way our cities are built? Don’t neighborhoods change slowly? Isn’t transit expensive and doesn’t its construction take forever? How realistic is any plan that begins with changing the fundamental land-use patterns of many of our communities?

These objections make sense — if we take the past as a guide. Decades of public debate and pop culture have defined cities in our minds as places that struggle with poverty, decline, and “white flight”; places that are desperate for any economic leverage, and need to build every casino, stadium, urban mall, and parking garage they can to attract suburban shoppers and business investment; places that physically change only incrementally and in a scattershot manner. We see cities as sickly, weak, barely hanging on. In fact, this view of the city is outdated and inaccurate.

We are now entering the largest worldwide city-building boom in history. Here in the United States, the Census Bureau predicts the population will grow to as much as 365 million people by 2030; 85 to 90 percent of them are expected to live in urban metro areas. In much of the developing world, a transformative explosion in city-building will likely happen between 2030 and 2050 — as rising urban populations meet growing economic capacities — but in the U.S. that urban surge will happen in the next two decades.

“More than half the built environment to be seen in 2025 did not exist in 2000,” says the demographer A.C. Nelson. “During the next generation planners may have an unprecedented opportunity to reshape America’s built landscape.” And because of the housing bubble and the Great Recession, only a tiny amount of the needed construction has begun over the last few years, meaning that most of the new building we’ll need to meet this population surge has yet to break ground. This “unprecedented opportunity” means that big thinking is the only realistic kind of thinking to do.

Not every city will grow. Here in the U.S., some industrial cities seem likely to continue their decline because of economic transitions that have been decades in the making and will not be easily reversed. Others will find they’ve made decisions that start them down a different path of decline as their suburban tax bases decline and auto-dependent systems become more and more expensive to maintain. (Indeed, I anticipate that the decline of auto-focused cities over the next decades will be a national crisis of the same magnitude as the hollowing-out of the Rust Belt, although it’s a crisis we could largely avoid with bold action now.) Others still (especially in the American Gulf Coast states and the desert Southwest) will find life made difficult by changing climate conditions: droughts, dust bowls, water shortages, worsening tropical storms, invasive species, and new infectious diseases. Some places will actively try to limit growth by making it harder to develop in existing communities (a strategy which only leads to a nasty combination of rising costs of living and more sprawl). A growing urban population is not a tide that will lift all boats; it may send many struggling boats against the rocks.

Successful urban regions, however, will grow more rapidly than ever before, seeing their populations swell by hundreds of thousands, even millions, of new residents in just the next few decades. All those people will need homes, workplaces, hospitals, schools — and transit to connect these venues. Cities and regions that embrace the opportunity and make smart choices about where and how to build will have a once-in-a-century chance to reweave their urban fabrics.

The growth these new residents bring can reshape whole neighborhoods, provide the revenue for investments in new infrastructure and systems, and stoke the fires of a bright green American economy. The coming boom can release a revolution in urban innovation.

And this boom will be largely urban. A huge cultural change has happened in the last 20 years, and we’re only now beginning to understand it: People, especially young people, now greatly prefer walkable urban-core neighborhoods to car-focused suburbs. This is true even in North America, where the conventional wisdom has been for years that most people prefer suburbia. Studies show millennials want not dream homes, but dream neighborhoods. Recent Census Bureau stats reported, “64 percent of 25- to 34-year-olds look for the city they desire to live in before looking for an actual job.” The 2011 Community Preference Survey, the largest and most in-depth real-estate poll in the U.S., also shows a dramatic shift: “Seven times more people say the neighborhood where a house is located (88 percent) is a bigger consideration in deciding where to live than the size of the house (12 percent) … More than three-quarters of the public (77 percent) consider having sidewalks and places to take walks important … Young singles (under 35) are especially likely to [place the highest value] on a neighborhood with a mix of houses and businesses.” This trend is most pronounced for the young people cities most want to attract. A 2011 CEOs for Cities study found “In 2000, young adults with a four-year degree were about 61 percent more likely to live in close-in urban neighborhoods than their less-educated counterparts. Now, they are about 94 percent more likely.”

At the same time, we’re changing not only where we live, but also how we live. People are living longer, having fewer kids later in life, and living in nontraditional households and relationships. Families with young kids at home make up only about one-fifth of American homes, according to the latest census. Expectations about what makes a good childhood have changed as well: Many younger parents now see urban childhoods as better than suburban ones (they’re certainly safer — kids are much less likely to die in or under a speeding car when they live in a walkable community). The result of all this societal change is that demand for smaller homes, townhouses, studios, and lofts seriously outstrips supply. Indeed, some real estate experts say there’s a latent demand for tens of millions more units of urban housing than we have, while perhaps as many as 40 million unwanted suburban homes continue to see dropping values.

All this means that the coming city-building boom is really a boom in people-focused, compact communities. Indeed, one factor that’s keeping many cities from growing is simply cost: With supply lagging so far behind demand, housing in walkable neighborhoods commands a steep price premium. One study commissioned by CEOs for Cities found that a one-point increase in a home’s Walk Score (which rates a place’s walkability on a score from one to one hundred) corresponds to an average increase of $3,000 in that home’s value. With such a gap between housing demand and supply, walkable neighborhoods are simply financially out of reach for many people who would like to live in them, and are increasingly becoming too expensive for the less wealthy people who live there now.

The answer to this problem is simple: Build more housing. The simple truth is that if you want home prices to drop, or even just level off, the only way to do this is to build more housing. Every known policy aimed at limiting housing costs — from rent control to tenants’ rights to development moratoria — has failed to stop the rise in housing costs. Some of these policies have other merits (I think tenants’ rights ought to be strengthened in most cities), but none can do anything about the central dynamic, which is that in a city with extreme housing pressures, every sale of a property drives out a lower-income family and replaces them with a higher-income family; if that city has added little new housing supply, the lower-income family’s only option is to move out of the city to where housing is cheaper. Desirable cities in growing regions either add housing rapidly or become unaffordable and socially inequitable. It’s that simple. Limited housing supply is what drives out the poor.

A major factor limiting compact development, though, is that many people — especially older people — still have mixed feelings about growth, and fear that more development will “ruin” their neighborhood. At first glance, this makes intuitive sense: lots of new growth in a small area might seem like a recipe for neighborhood decline. It is definitely possible to design bad buildings — we’ve all seen an eyesore replace a cherished landmark somewhere in our town. Buildings can be ugly and imposing; when they are sited badly, lack pedestrian amenities, and offer no public or commercial uses at the street level, they can even become a form of “vertical suburb,” wherein they remain auto-dependent despite their density. That problem, however, is solvable with good planning and higher expectations of developers (expectations they’re often happy to meet if in return they’re given speedier permitting for their projects).

Bad buildings are one thing; bad streets are entirely another. Though we may not know the term, we have all experienced the “paradox of intensification.” As density increases, the number of people who choose to walk, bike, or ride transit also increases, but traffic increases as well (albeit more slowly). New walkable areas emerge, but many residents still need to drive; people from outlying car-dependent suburbs still want to drive through the neighborhood; old drive-in businesses still draw traffic; and parking is harder to find, meaning more cars circling looking for a spot. Often, new residents arrive before the businesses and amenities to serve them, meaning favorite parks, cafes, and restaurants get crowded. Clashes between pedestrians and drivers not used to negotiating urban settings become more common. The result is that a little density, arriving slowly, can end up making a neighborhood more congested with traffic, noisier, more dangerous, and less pleasant.

These are the perils of incrementalism. Small steps and gradual change may seem to take us “in the right direction” but may actually be more difficult (and arouse more local animosity) than making a larger change quickly. The main way incrementalism fails in this context is when planners try to “balance” the needs of cars with the needs of people walking, riding their bikes, and using transit. No such balance exists. As you add density, auto-dependence demands more and more parking spots, increased road capacity, and fewer impediments (such as traffic lights) that “get in the way” of cars. Without these, driving as we’re used to it in suburban settings only gets worse as more residents arrive, adding more cars to the streets.

Car-free places

We can’t build our way out of these traffic jams. We can bypass traffic, though, by creating other options for mobility. Driving will simply never get easier in a dense city. The only known fix to this problem involves remaking the streets for people, not cars. We know that with just basic pedestrian infrastructure (like sidewalks and streetlights), people will begin to use transit at about 12–15 units per acre. But we also know that this “transit-supportive density” is just one tipping point. If within key neighborhood cores (or along important corridors), cities aggressively tip the balance toward making streets that are designed to slow traffic, limit cars, and make for wonderful pedestrian-focused places that are well served by transit, at a certain density level — hotly debated, and in my opinion partially determined by culture and climate, but generally thought to be between 30–40 units per acre — many people will choose to get rid of their cars altogether, and most people will choose not to drive for most trips. Transit-supportive densities transition to car-free densities. That’s correct: Plan well and build quickly, and many people will simply use their cars less or get rid of them.

Urban people make these choices on their own — when their cities work well. Simply increasing density and focusing streets on the people walking and biking will set these changes in motion, as more and more residents find it preferable to leave the car at home for most trips, and more people passing through the neighborhood find it better to either take transit into the area or to simply find another route to get where they were driving. (A certain amount of “geographic sorting” has already begun taking place, with a certain number of people who feel driving and cars are essential moving from cities to exurbs that still have wide arterials, big parking lots, and highways — a topic I’ll come back to in a future project.) The more friendly the neighborhood gets to people on foot, bike, and transit, the easier it gets for others to decide to make the switch.

This is what’s known as a “threshold effect,” a paradoxical situation wherein a bit of change makes things inconvenient and slightly more change can produce some serious negative side effects, but lots of change actually improves substantially on the original situation. A few more people living closely together but still driving makes street life worse; many more people living more closely together in a great neighborhood, though, ends up reducing traffic. The more people who live without cars (or don’t use them much), the better the neighborhood gets as it densifies.

Areas designed to support car-free lifestyles can end up giving people more mobility. This is totally counterintuitive for most North Americans. A century of advertising and six decades of planning focused almost entirely on cars have convinced us that cars are always the quickest, most convenient way to get from one place to another. Indeed, most transportation planning is actually traffic planning — its only and entire goal is to move as many cars as possible in the shortest amount of time. To the average old-school transportation planner, the city’s main job is moving cars. Many traffic models don’t even count people biking and walking, much less the effect of bundling their trips on a neighborhood walk; some don’t even count transit. In short, both our cultural expectations and the traditions of road engineering tell us that cars are transportation, and therefore, anything that reduces cars must reduce mobility, and anything that reduces mobility must impoverish us. Slowing, much less limiting, cars is disastrous (they claim) and will lead inexorably to gridlock and economic losses.

The reality is that travel times can actually improve with fewer cars. Streets designed for pedestrians, bicyclists, and transit can accommodate many more people, moving more quickly, than can congested, car-focused roads. (This is one reason why “bus rapid transit” (BRT) works so well. Buses can fly through the city, moving many more people than cars could, when they have lanes of their own.) More users means better transit service, with more frequent trains and buses (“shorter headways” in transit-geek terms), better connections and transfers, and more express routes — all of which means it takes less time to get from one stop to another. In many places with bad traffic, biking (or even walking) is already quicker than driving some routes. With safer streets where pedestrians and cyclists get shorter paths, less waiting time at lights, and more areas with no cars at all, many routes will get even quicker. A low-car city can be a faster one.

These trends can be reinforced by creating congestion pricing zones where drivers are charged a toll for using the streets — even with traffic calming obstacles and more road lanes devoted to public transit, tolled areas can actually end up with less traffic than they began with, as was the experience in London. Eliminating free parking and allowing new developments to be built without parking in the first place — free/cheap parking is an inducement for people to drive — can help reduce the number of cars on the road at any one time even further. Narrower streets with fewer cars don’t always lead to less traffic, but these trends do mean that low-car cities don’t have to be driving nightmares.

Low-car cities don’t eliminate cars, but they do put them in their proper urban context. Some cars are likely to be a part of our cities for the foreseeable future. Whenever we have a choice, though, between making it easier to drive and making it easier to walk, bike, and ride, the cars need to make way. Perhaps most importantly, urban streets should constantly remind drivers that when they do get behind the wheel in cities, they’re moving through people-focused places, and must exercise responsibility and care.

A top priority for any neighborhood should be reducing the speed at which cars move through its streets. For one thing, faster cars are deadlier cars. When a driver going 20 mph hits a pedestrian, the pedestrian’s risk of dying is roughly 5 percent; when a driver going 40 mph hits someone, that person’s risk of death rises to 80 percent. Driving faster is particularly deadly to young children, who, studies show, have a harder time seeing and anticipating fast-moving cars. Car-on-car collisions, too, are more likely to be deadly at higher speeds. (The higher risk involved with fast-moving cars is one reason why the statistics show suburbs are now more dangerous for children than urban-core neighborhoods.) Finally, fast traffic is noisy, unpleasant, and stressful for those on the sidewalks of a busy street — it’s a nuisance as well as a danger.

The answer is not lowering the speed limit. It’s not street signs indicating pedestrian crossings. It is not even more stoplights. All of these are useful tools, but the real answer can be found in changing the shape and feel of the streets themselves. Widening sidewalks and reducing the number of lanes of traffic — the so-called “road diet” — makes drivers pay more attention and feel the need to slow down. Putting in speed bumps, obvious crosswalks, and curb bulbs at pedestrian crossings does, too. Planting street trees and other features that “crowd” the road, making drivers feel higher speeds are more stressful, also does the job. When drivers feel they must pay attention, they drive more carefully and slowly; a fair number of drivers who were just passing through on their way to other locations will simply begin to avoid the area. All of these things have the added benefit of making the neighborhood more walkable.

Better still are places where cars are either forbidden, or are given an obviously low priority. Many cities around the world have older cores where cars are only allowed for commercial purposes or if owned by a resident. Often, these streets are closed off to cars by automated bollards that can only be opened with the right electronic passes. Other cities have embraced design strategies that make an entire street a pedestrian zone, essentially one giant sidewalk through which cars can pass, but only carefully, and slowly. Still others have simply banned cars from certain roads or at certain times of day, creating part-time pedestrian boulevards. And many more efforts to build strongly people-focused cores are on their way. Cities from Singapore to Vancouver to Melbourne are looking at ways to create large shifts away from the private car, while the European Commission has put forward a strategy for all cities in its jurisdiction to create plans that will completely remove all gas-powered cars from their centers by 2050. Meanwhile, significant shifts in opinions about car ownership and usage have already occurred, with fewer and fewer young people even getting drivers’ licenses, and the number of vehicle miles traveled dropping steadily in some cities. Many urbanites already want people-focused, even car-free, communities.

The threshold effects of people-focused density make building more of it the single most critical task for carbon-neutral cities. If we’re going to see the shifts in transportation choices that are pivotal to addressing the climate challenge, we need to design policies to quickly turn car-dependent areas into vibrant compact walksheds. That means our cities must grow denser. In a perfect world, this density would simply spring up because it’s needed and wanted; in this world, though, density doesn’t happen magically on its own, even when there’s a gigantic demand for it.

Ecodistricts

One way to build more density quickly is the creation of new “ecodistricts.” Often built on “brownfield” sites (like old military bases, vacant industrial land, abandoned ports, or dead malls), ecodistricts offer a great advantage: by building an entire neighborhood from the ground up, planners can use the latest infrastructure and planning from the start to make these areas people focused and transit friendly. Some districts — like the Vauban neighborhood built on a decommissioned military base outside of Frieburg, Germany — have been designed from the start to encourage minimal dependence on cars (living in a compact community with bike lanes, pedestrian streets, and a new tram into the central city, 70 percent of the families in Vauban don’t own cars). Others have emphasized energy efficiency (like districts in Malmö, Sweden, or the Dockside Green community in Victoria, British Columbia) or sustainable waste management (like the Hammarby Sjöstad area of Stockholm). We’ll come back to this idea of district systems. It’s important. Cooking up a new neighborhood with new infrastructure and sustainable transportation planning baked in is almost certainly the easiest recipe for a bright green urban community.

Unfortunately, opportunities to build a whole community from scratch are relatively rare. Every city probably has a few large sites ripe for ecodistrict redevelopment, but not many thriving cities have more than a few. If we’re really going to change the fabric of a major city, we need to talk about remaking existing neighborhoods, bringing them up to the level of people-focused density needed to support transit and new infrastructure. Sustainable urbanism most often means reweaving an existing, worn fabric, not producing new cloth.

Those with experience in North American urban politics, though, may understandably despair of the idea that we can bring entire neighborhoods up to 30–40 units per acre, when many are now less than 10 units per acre and so many challenges stand in our way. In many cases, because of a wide range of factors, including limited public resources, the perils of incrementalism, the slow speed of change in commercial development, and Not In My Back Yard (NIMBY) politics, increasing densities over an entire area consistently and quickly seems essentially impossible. But is it?

Smart neighborhood infill

Spreading density evenly, like butter across a piece of bread, is only one approach to transforming a given walkshed. The average person is willing to walk only half a mile at most for most trips. That means that her walkshed is essentially a circle a mile wide around her home. That area contains a little more than 500 acres. If we were to raise the density everywhere in her walkshed from an existing average density of say 10 units per acre to 30 units per acre over the course of two decades, every single block would have a number of new buildings (or significant remodels) on it.

Technically, there is nothing preventing us from doing this, and improving neighborhoods in the process. We certainly can make older neighborhoods better with lots of small interventions that add new residents. Larger homes (for which there’s less demand as average household sizes shrink) can be split into apartments and condos; small backyard cottages can be built; basements can be converted (or second stories added) to create new modest apartments or “granny flats”; new townhomes and small apartment buildings can replace vacant lots (or tear-down buildings) and be designed in such a way that they feel part of the existing fabric of the neighborhood. Combined with traffic calming, bike lanes, street trees, and green spaces, good infill development can ensure that neighborhoods retain their charm while reaching people-focused density.

The problem is that in practice, urban politics often makes this almost impossible to do in the time we have. Subdividing homes and redeveloping small lots can only happen at a slow pace, as properties become available. Permitting, planning, and infrastructure costs are high for local government, since almost every new project is particular and costs more staff time while new tax revenue is slow to arrive. NIMBYs may oppose new cottages and townhouses. Developers may be reluctant to risk money on complicated infill projects when easy money can still be made building elsewhere. We should certainly continue to encourage good fine-grain neighborhood development; we just shouldn’t expect miracles. If we want people-focused densities within the next couple of decades, we need to look to a more innovative set of approaches.

Tentpole Density

A non-intuitive characteristic of density is that it works on averages. You can get to 30 units per acre in a walkshed by having every acre covered with 30 units, or by having a single 300-unit building sitting on 10 acres of land. That means (with good placemaking) a few dense places can make a whole area perform like a more compact community. A dense neighborhood core (like an old small town “main street”) can raise the whole community around it to people-focused average densities. Like a tentpole, this compact core lifts the effective density of the urban fabric around it, even if those surrounding blocks don’t change very much.

Consider a hypothetical: A 500-acre walkshed that is currently at an average density of 10 units per acre could add just two units per acre (almost imperceptible — a couple of basement granny flats or backyard cottages on each block) to most (400 acres) of its area if it made its neighborhood core really attractive to new development. If, in that center, a people-focused core was 180 units per acre (six- and eight-story mixed-use buildings over a 40-acre area), and a surrounding belt of blocks was 60 units per acre (with a mix of townhouses, cottages, and small condos, say), the neighborhood’s average density would rise above 30 units per acre. The overall effect would be that everyone in that walkshed would have a people-focused community — but 80 percent of the neighborhood would look no different.

Or think about it another way: Imagine you live in the “bungalow belt” of older homes in a single-family neighborhood that grew up around a streetcar line. You love your block, with its classic homes and old trees. You can walk five blocks to a nice little “main street” with a few shops, a cafe, and a bar or two, but that little neighborhood core doesn’t offer access to everything you need. There’s no grocery store within walking distance, say. You would take transit downtown to work, but the bus only comes every half hour. The nearest decent daycare is a 10-minute drive. As a result, both you and your partner have cars, you drive almost everywhere you go most days, and your daily drives take you past run-down strip malls, parking lots, and a lot of wasted land just outside your neighborhood. This is a typical scene for many people in North American cities.

Now, imagine the same neighborhood, but with those strip malls redeveloped, those parking lots turned into mixed-use buildings, and that wasted land used for infill development. Now, you have not only your “main street,” but also a whole corridor of people-focused buildings within walking distance. The thousands of new residents who live there make an enticing market, meaning that a grocery store opens up on the ground floor of one of these new buildings; child-care options improve; there are more places to dine out. Due to increased demand, the bus now runs every five minutes. New stoplights are installed and more street trees are planted. A new park is being built with the increased local tax revenue, and more young parents mean the school system is pressured to improve. Your actual living situation has barely changed, if at all. You still live in a little bungalow on a quiet street with big trees. Except now you and your partner find it easy to get rid of one of your cars, and you drive a lot less (and save a lot of money). You now live in a people-focused community.

A dense neighborhood core is, of course, only one of many possible patterns. Some cities focus on creating these neighborhood-centered “urban villages.” Others focus on key corridors, stringing compact development along key roads and creating linear density. Still others group most of their new density in smaller clusters along new transit lines. Forms can (and should) vary to reflect local cultures and conditions, but the operating principle remains the same: The key is to concentrate on spots where enough growth can be clustered to create transformation throughout the local area.

Tentpole density means we don’t need to completely remake every street — let alone convince every person to change her behavior — we just need to concentrate our efforts on building walkshed cores that can offer access by proximity and many more choices to nearby neighbors. Tentpole density can provide critical mass for new transit, infrastructure, and business investments. These tentpole neighborhood centers make a ton of financial sense to local government. They can be much more easily planned, permitted, and financed than myriad small projects, and be built more quickly at a reasonable profit (while adding to the local tax base). They can also be built simultaneously with new transit, street improvements, and amenities paid for by borrowing against the new tax revenues they will generate — an old, proven technique known as “tax increment financing.”

When new buildings tip the balance in their own walksheds, they not only improve quality of life in the immediate area, they also offer benefits to the surrounding neighborhoods. People in nearby walksheds gain new destinations for shopping and entertainment. The transit routes, walkways, and bike paths that connect these cores together mean bikers and transit riders in other neighborhoods along the way get better service. As more businesses catering to car-free customers (by, for example, offering free delivery) locate in the area, residents who want to drive less benefit, wherever they live. Retrofitting even a dozen such people-focused neighborhoods can redraw the transportation picture of an entire city.

The placemaking dividend

A critical mass of people-focused neighborhoods can also power economic reinvigoration. Simply put, people-focused density is economically more competitive. Numerous examples show that sidewalk-focused retail (restaurants, small shops, local professional services) does better as density increases and the area becomes more walkable. The idea that urban neighborhoods need to “compete” for suburban shoppers by providing lots of free parking and widening streets to ease traffic is outdated and counterproductive. The fact is, at a time when suburban retail is crashing, urban retail is beginning to boom.

Indeed, the “placemaking dividend” retail businesses get by being in a walkable neighborhood can be huge. From Vancouver to Copenhagen to Melbourne, dense walkable neighborhoods have become entertainment destinations, drawing people from around the metro region to new restaurants, bars, theaters, and arts institutions. New York City Department of Transportation’s Janette Sadik-Khan reports that the stores lining the newly closed-to-cars streets in Manhattan saw sales increase 71 percent in just one year, and the effect is now spreading to nearby streets. Even as the number of new auto-dependent supermarkets has plunged in recent years, smaller pedestrian-focused (and, more frequently, locally owned) urban grocery stores are multiplying.

What’s more, in many places, the success of the cores of these neighborhoods has enlivened businesses at their margins. There’s a “spillover effect” that can help more entry-level small businesses thrive in the cheaper edge locations. This means immigrants, artists, and others often find more opportunities in these areas, despite rising rents — especially if local government makes helping them a priority (by, for instance, encouraging mobile food carts, or making small business licensing easier for small stores, art studios, and temporary retail).

All of this means more money stays in the local economy, generating more jobs and prosperity in turn. Even the construction involved in walkable cores is better for the local economy. A 2010 study shows that building bike lanes creates 14.4 new jobs per million dollars spent and widening sidewalks means 11.3 jobs per million bucks, while road upgrades and repairs only create 7.4 jobs per million bucks. Some highway projects generate less than three jobs for every million dollars in taxpayer money spent.

And once these walkable centers are built, they provide much more revenue for our local governments than spread-out, auto-dependent development does (studies show that compact, mixed-use development generates far more sales and property-tax revenue per acre than low-density uses like strip malls and single-family streets), while costing much less to maintain (the infrastructure costs per resident are much lower in compact communities, because more people can share the same sidewalks, pipes, and wires, much more efficiently). Compact development simply costs less to serve and provides more money for our parks, schools, libraries, and emergency services. In other words, walkable centers provide a foundation for better governance.

Walkshed technologies

The same walkable places also provide fertile ground for technological innovation. Mobile and ambient technologies (our cell phones and laptops, embedded sensors, database technologies, augmented reality, and so on) not only thrive in people-focused communities, they multiply, intermingle, and evolve. These “walkshed technologies” are morphing the ways we live in people-focused places. They’re changing cities irrevocably. And mostly, this is a very good thing.

I’m old enough to remember a time before Google. Back then if you wanted to find something on the Web, you had to go looking for it, using these sites called “directories.” You would pull up a directory, click on a category of thing, and then go one by one down a list of webpages until you found something like what you wanted. The Web was “browsable,” but not “searchable.”

Today, that seems utterly absurd. Yet until the explosion of smartphones about five years ago, nearly everyone still used cities like the Web before Google. If you were out shopping and wanted to find which store had the best price on an item, for instance, you generally had to either call the stores one by one or go around and compare their prices in person. Even at home, most people still used the Web like the phone book, finding the number for a store or restaurant online then calling and asking them if they had the right product or an open reservation.

Today, every smartphone is essentially a small computer. Every phone can access maps, reviews, retail offerings, service data, and a whole host of other facts and opinions about how things work in a given city. And phones are now ubiquitous: according to the International Telecommunication Union, there are now 5.9 billion mobile subscribers worldwide (the number of total users is less, but 85+ percent of all people now have access to a phone). Our cities are now, as Adam Greenfield says, searchable.

On the most basic level, technology has simply dematerialized a bunch of trips we used to make. For instance, fewer and fewer people drive to a music or video store since they can download music and stream movies. Other trips we used to make have been replaced with home delivery. Most purely functional shopping can now be done online, with the products you buy delivered to you. Because one truck driving multiple places (often on a computer-generated route designed to take the least time and use the least fuel) is far more efficient than many people driving themselves around to shop, home delivery is inherently more sustainable. Delivery is even getting more secure, with innovations like the German Postal Service’s packstations or Amazon’s “delivery lockers,” which keep deliveries in secure neighborhood kiosks until you pick up your parcels with a swipe card. If we live in walkable communities, we can now get most of the things we need in life without even owning a car (I suppose many of us could get most of the things we’d like to purchase without leaving the house).

When we do want to go out for a bit of “sport shopping” or “retail therapy,” it’s easier than ever to have the things we buy while out and about delivered to us — indeed, some stores are now simply “webfronts” designed to give a tactile, personal experience to online shopping by letting us handle the products or try on the clothes before we buy them online. Shopping is less and less about driving around and filling up the car trunk than it is about taking transit to a retail district, meeting a friend and making a day of it, walking around and checking things out, having lunch, people-watching, having a drink and relaxing. Increasingly, it costs less to have a thing delivered than it does to pay for parking. In fact, the very degree to which physical shopping is becoming an experience rather than a necessary chore may drive rapid innovation in how retailers connect with, serve, and entice their customers. As Dan Hill puts it, “physical experience had better be bloody good if it is to withstand the force of the internet.” Shopping streets now survive by being great places to walk around and have fun.

But that’s not the limit of how technology is changing our relationship to space and transportation. Done right, dense cities with good technology actually become easier to move through. In fact, they’re changing the very nature of what it means to move through urban space.

It’s a common observation in some tech circles that this will be the last generation to know what it means to get lost, since phones with GPS-powered maps and travel information are ubiquitous and constantly available. What is less remarked is that this is probably the last generation to frequently experience unintentional urban solitude, and certainly the last generation to unwillingly experience the true sensation of being alone in a crowd. We nearly all carry access to enormous amounts of media around with us, allowing us to create our own emotional bubbles whenever we like. Most of us are communicating somewhat constantly with friends, family, and coworkers through phone calls, emails, and texts. Already some of us move through heavily annotated urban spaces, where we can in real time know where our friends are and what’s going on that might be of interest to us. As urban technology accelerates, and begins to include more interfaces and means of interaction, I expect that what we view now as an imposing degree of connection will someday soon look quaint and cranky.

Not all the effects of this will be good. Indeed, I think constant hyperconnection may be in some sense damaging to our souls, distracting us from the messy and constant work of becoming ourselves. Heck, we’re still reeling from the societal impacts of old-school broadcast media, which sociologists like Robert Putnam have argued (convincingly) have been a terrific shearing force on our communities, associations, and civic life; the social effects of ubiquitous and always-on communication may magnify those impacts. Constantly being alerted to choices can make our lives extremely stressful, as we’re constantly reminded of all we’re missing. “Filter bubbles” applied to our lives in urban space may render cities less and less a place of encounter and exchange. I suspect that — just as being able to schedule long blocks of uninterrupted time is now taken as a sign of prestige and power in upper-middle-class culture — finding, or living in, urban space that is random and whimsical on the one hand, or peaceful and low-stimulus on the other hand, may become an increasingly sought-after experience. (All these forces actually have the potential to be far, far more harmful when combined with auto-dependence and the social isolation of suburbia, but that’s a story for another time.)

On the other hand, it’s possible that we may get a grip on these technologies and use them to make our cities much livelier, more nurturing places. There’s a lot of evidence to suggest that more online socializing leads to more friendships and socializing in “real life.” Some groups have begun to find ways to use technology to engage with people who’ve essentially stopped participating in civic and cultural life. Approaches as varied as geolocative art to gamification are trying to draw people back into engagement with each other in urban places. It may be that hyperconnection, properly tamed, makes us more a part of our cities than we’ve been for a century.

In any case, some of the effects of walkshed technologies will be unquestionably good when it comes to energy use. For instance, the one gigantic advantage cars have always had over transit is convenience. Walkshed technologies are fast eroding that advantage. Since buses and trains are easily tracked with GPS, it’s trivial to provide information about when the next bus or train will be at our stop, thereby minimizing the time we spend standing around and waiting. It’s increasingly easy to have the system plan the most efficient trip for us given the real-time positions of the buses or trains we’re choosing from and current road conditions, meaning that we get to our destination by the fastest possible route. In addition, for people who are often occupied using their laptops, tablets, and phones, Wi-Fi–enabled transit means time that would otherwise be spent focused on not crashing our cars can be spent being productive or just enjoying ourselves. Seen in this light, all driving is a waste of the time you could spend doing better things.

Walkshed technologies actually increase the number of options we have, compared to driving. If we really want to drive, looking up the nearest car-share vehicle is easy, and many systems allow walk-up use: Find the car, walk there, get in, and drive away. Taxicabs, too, are easier to order and (since they themselves are networked and tracked) more likely to arrive quickly; services like Uber give us access to fleets of cars we can’t normally hail on the street. Even ride-sharing services get much more realistic. Some futurists, again including Adam Greenfield, even see an emerging era of “cloud commuting,” where a host of travel options is available for a given trip, and people move effortlessly through the most convenient ones, not needing to plan their routes, much less memorize bus timetables and subway maps. With the right phone and the right app, transit is effortless.

Walksheds as innovation platform

Compact communities suffused with technology offer another advantage: They’re a superior platform for the widest range of innovations. This is counterintuitive — exurbs, with more land and cheaper rents, seem like they’d be much more amenable to experimentation. But we think this because we mistakenly focus on surface form, and neglect to look beneath the surface, to systems.

When we look at exurban systems, what we find is that they are incredibly rigid (and thus also brittle, but that’s an idea we’ll take up again later). Because suburbs are so spread out, with roads built in hierarchies of cul-de-sacs, feeder roads, and arterials, with different parts of life (like home, office, school, and shopping) separated and widely dispersed, most exurbs can only realistically be navigated by car. That means connections between points can only be made in one way, and the only thing we can really change about exurbs — without making them into something other than an exurb — is the mechanics of driving itself (and we haven’t done a very good job of that in the last half century).

Within more compact communities, though, the number of possible connections increases geometrically as more kinds of people and more potential solution spaces find themselves within proximity to each other. Replacing auto-dependence with walkability means replacing a single, rigid approach with a variety of approaches. That means more can be changed, which in turn means more things for innovators to improve. Especially in the cities that welcome innovations in deeper systems, like infrastructure, patterns of urban life can be made flexible, approaches to problem-solving can be iterative and influence each other, and rethinking root problems becomes possible.

If you want to innovate, do it where you find the most opportunities for innovation.

City innovation as transportation solution

By seeing the problem of transportation for what it really is — a problem of access, of land use, of the way we build our neighborhoods (in other words, a city-building problem) — we instantly redefine the available solutions. In just a few years, a neighborhood can go from auto-dependent to people focused. In just a few more years, cities can weave together their people-focused neighborhoods with deep walkability and transit routes. Within a few decades, a fast-changing city can deeply slash its energy use.

The changes needed are changes that improve people’s lives, changes many people want (and most people who live in cities are eager to see). We’re talking about growing nicer neighborhoods, with broad sidewalks and street trees and local businesses; places with a mix of homes and people; places that are less expensive to live in, yet offer more opportunities; places that are healthier, cleaner, and safer for our kids. And perhaps most importantly, on a planet in the midst of a climate catastrophe, places that emit many, many fewer greenhouse gases.

Read the sidebar to this chapter: People-focused places and fairer cities

Read on: If we build it right, they (emissions) will come (down)

Compact development means increasing the supply of housing. Even if the new homes are being built in an area not affordable to those with low incomes, the increased housing supply helps make other housing more affordable than it would otherwise be. Part of what we need to do to bring housing costs down is build a lot more of it (and refurbish more of what’s there).

Many people worry about gentrification. But the reality is that gentrification proceeds inexorably in walkable neighborhoods when cities have a very limited supply of people-focused areas. Lots of new development doesn’t make things worse: It means the gentrification that occurs is the kind that’s more likely to be beneficial to the people already living there. A recent Columbia University study found that “poor residents and those without a college education were actually less likely to move if they resided in gentrifying neighborhoods” in part because the increase in services improved their lives more than the rising cost of living disrupted them.

Good development can benefit low-income people, too, because compact neighborhoods are cheaper to live in; and the more compact they get, on average, the more the cost of living drops, measured against suburban areas with comparable income levels. We’re used to thinking of the suburbs as more affordable, because homes on larger lots cost less there. Think of the saying, “Drive until you qualify,” which acknowledges that real estate prices drop the farther into the ‘burbs you go.

Suburban affordability, however, is an illusion — when you consider the whole cost of living (and not just home prices) the suburbs are often actually more expensive. The average American family in an auto-dependent neighborhood spends more than one-quarter of its income on cars (not counting secondary costs, such as the health costs of so much inactivity and the financial risks of a major car crash). The average family in a walkable community, on the other hand, spends only 9 percent of its income on transportation — and their choices tend to leave them healthier and better off. The costs of car ownership, especially multiple car ownership, are so great that even when housing is much cheaper in the outer suburbs, the cost of living is greater.

And cars are arguably the one product most responsible for impoverishing the poor in the first place — an “investment” that destroys much of the value paid into them, and moves money out of the local economy. Cars funnel money from poor drivers to auto companies, lending companies, oil companies, and insurance companies. As Catherine Lutz and Anne Lutz Fernandez write:

The car system redistributes wealth upward, playing a significant role in the creation of inequality in America … Cars are an expensive and depreciating asset for which there remains pervasive discrimination in new and used vehicle pricing, financing, and insurance. In other words, someone with low income or living in a poor or minority neighborhood will likely pay more to own and operate the same car than someone holding a higher-paying job or living in the next town over … In a lifetime of car ownership, an American family will likely “invest” almost $1 million in its vehicles. And these numbers don’t even count yet more hidden costs like the mortgage on our garages or the property taxes levied on them.

There is a huge cultural challenge here: In an auto-dependent world, the working poor are understandably reluctant to give up their cars, even though they’re much more likely to achieve middle-class status with less auto dependence.

Being priced out of scarce homes in walkable neighborhoods and valuing the status and sense of “spatial freedom” that can come with a car, lower-income Americans are migrating to inner-ring suburbs and outer-ring exurbs.

One of the innovations most needed is a strategy that makes it possible for auto-dependent, middle- and lower-income families to live in and benefit from walkable communities, especially where the upfront costs of moving there are greater. I don’t know of such a program anywhere, but it could offer real traction on a growing problem. Even such a smart strategy for helping the working poor live more affordably will fail, though, if cities don’t build many more walkable neighborhoods, with a much greater supply of housing.

Back to Carbon Zero, chapter 3
Full table of contents for Carbon Zero

Before we get on with the business of reimagination, though, we have to pause for some clarification on the matter of energy.

The first response many of us have to the climate crisis is simple: We need cleaner energy. This is not illogical. Most of the emissions warming the Earth come from burning dirty fossil fuels. So, we think, replacing those dirty power sources with clean energy sources should solve the problem. When we first ponder the challenge of making carbon zero cities, most of us fly immediately to the idea of cities covered in solar panels and powered by fields of wind turbines.

But seeing climate change mainly as an energy-generation problem — rather than an energy-use problem — will mean failure. To meet the climate crisis and win, we need to not only change the kind of energy we use, but also (and even more importantly, to my mind) completely rethink our relationship with energy.

The clean energy supply challenge

My support for clean energy is unequivocal. Obviously, we need to be moving quickly towards a world where all the energy we use comes from clean sources. Wind, solar, geothermal, and hydro all have very, very low emissions. (Nuclear is less climate-friendly, once the costs of mining uranium and storing the waste for the necessary 25-100,000 years are factored in, but some smart people like to include nuclear in the clean energy mix.) A world that ran only on these energy sources would be profoundly more sustainable.

Here’s the problem: If we continue using energy as we have, we won’t become a world run on clean energy. Business as usual, according to the U.S. Energy Information Administration (EIA), would see global energy demand jump 44 percent by 2030. The International Energy Agency (IEA) warns that with current policies we may see more than a doubling of world energy use by 2050.

In other words, to “zero out” our emissions solely by using clean energy, we’d have to replace all the dirty energy used on the planet today — the coal, oil, and gas which provide transportation, heating and cooling, electricity, food, and manufactured goods to 7 billion people — with solar, wind, and other clean energy. Essentially we’d need to replace all of the energy used everywhere on the planet. And then — because energy demand is expected to double by 2050 unless we change direction — we’d need do it again, within the next 40 years.

That may be impossible, given even the boldest plans for clean energy production. Energy entrepreneur Saul Griffith gives an excellent talk (available here) in which he illustrates how enormous a job it would be to meet our current energy demand — much less doubled demand — with clean energy sources. We’re talking, after all, about amounts of clean energy generation that are hard to even fathom, much less plan for: forests of wind turbines off all our coastlines and blanketing the high plains, huge fields of solar panels, nearly every river on Earth dammed, and so on.

It’s true that clean energy innovation is proceeding at a rapid pace. I believe that as clean energy generation drops in price, simple economics will drive a shift to solar and wind. I believe carbon pricing, the elimination of fossil fuel subsidies, and changes in public opinion can massively accelerate that shift. But I don’t believe this will happen on a large enough scale, quickly enough, to make clean energy production the sole (or even primary) focus of climate action while world energy consumption doubles. That’s absurd.

The brutal realities of energy politics

For one thing, some of the largest companies and wealthiest people on the planet are determined to slow the spread of clean energy. These powerful interests are actively hostile to clean energy deployment, have war chests of tens of billions of dollars, and operate what’s probably the nastiest, smartest, best-funded political lobby in history.

If we bet on clean energy as our climate strategy, in order to win we must produce massive amounts of clean energy very quickly; yet our ability to get new clean energy sources up and running brings us into direct conflict with forces (oil prices, national regulators, financial markets, international agreements) that are often largely out of our control. The energy sector is especially subject to political delay, and in the U.S. and Canada, clean energy shows no sign of breaking free of the political logjam.

It’s true that external events might break up that logjam for us. The wildcard here is oil prices and their effects. Since we are likely past peak production of oil (and the oil supplies that remain are increasingly lower in quality, harder to get to, or both), prices are essentially certain to rise over time. The only question is by how much. The EIA forecasts oil prices rising to $110 a barrel in 2015 and $130 in 2030. Many other forecasters see much higher oil prices, up to $200 a barrel or more by the end of this decade.

Quickly rising oil prices will make transitioning to more efficient energy uses and clean energy sources easier. Slow-rising oil prices will make it harder. For oil companies, the ideal is that prices rise enough to make them maximum profits without rising high enough to spur a rapid transition. As Saudi Prince Alwaleed bin Talal admitted recently to CNN, “We don’t want the West to go and find alternatives, because, clearly, the higher the price of oil goes, the more they have incentives to go and find alternatives.” (Alwaleed also owns the fourth-largest stake in Rupert Murdoch’s News Corp, which may help explain some of that company’s climate denialist stances.) Another lead Saudi official told Reuters that climate treaty negotiations are “one of the biggest threats that we are facing.”

The worst-case scenario is that prices remain low for a decade or two, then skyrocket. That would mean rising emissions, followed by a severe strain on the global economy, making transition more expensive and difficult, and it would likely lead to an economy that has high emissions and low growth. The best-case scenario would see steadily rising costs starting now, so that we have the ability and incentive to transition quickly. Which scenario plays out is, unfortunately, essentially out of the control of advocates, and even most national governments. Politics severely constrains our ability to choose our energy sources.

The other energy path

We can choose how we use energy, though.

I’m not talking about efficiency — if by efficiency, we mean doing the same things, better. We tend to think of our economy and its energy demand as more or less a given, and efficiency gains as something that happens slowly and incrementally to improve that economy. For instance, many economists make predictions with apparent confidence that in order to generate X amount of economic growth we will need Y amount of energy. The theory is we’re already doing the right things; all we can hope for is to do them a little differently, a little more efficiently. (Others, like Amory Lovins, say we can do them much more efficiently, but most efficiency experts still see the overall patterns of our lives changing little.)

The way we live now, though, is not the pinnacle of prosperity: Progress didn’t end with 20th-century city-building approaches. Sprawl, malls, and highways aren’t the last word in wealth.

The greatest lever for changing the nature of prosperity is our cities. Cities abound with opportunities for transformation. In fact, the workings of almost every system in almost every city can be redesigned to use less energy while leaving us more prosperous.

And using less energy means a lot less demand for energy generation. Designing out energy and materials use within a city creates cascading reductions all the way down the supply chains that serve that city. Because these supply chains are full of waste (no industrial process is perfectly efficient and many industrial systems today pay at best passing attention to energy efficiency), reducing the need for the final product in a system often produces incredible savings as that reduced demand echoes out.

Let’s look at an example. When we turn on an air conditioner, the energy used to cool the room is a small fraction of all the energy used to power the machine. How? First of all, engineers tell me even the most efficient air conditioners only put out about one-quarter as much cooling energy as the energy they take in; the rest is wasted in the process of cooling the air. But in order to produce even that blast of cold air, electricity flowed into the home through the power grid. Along the way, energy was wasted in transmission line losses. The power plant on the other end of that power grid usually wastes vast amounts of energy generating electricity (coal-fired plants can waste half of the energy they generate by burning the coal that feeds them). The result can easily be that 10 times as much power is generated as is actually used to cool the room. This doesn’t even begin to account for the energy costs of manufacturing air conditioners, stringing power lines, mining coal, or building power plants (or maintaining that whole system).

As long as we rely on that air conditioner alone to make a building livable on a hot summer day, the best we can do is try to make each of these steps (power generation, electricity transmission, air conditioner operation) less wasteful.

However, as we’ll see in the second chapter, the building itself can also change. Buildings can be designed (and retrofitted) to require much less air-conditioning (or even none). Cities can be landscaped and designed to keep urban temperatures lower. And, of course, cultural norms can change from expecting a chilly but stuffy room in the middle of summer to being happy with a not-too-warm room that has natural ventilation. A city with buildings designed for natural cooling, shaded by street trees, and lived in by people who don’t expect to wear wool suits in midsummer — such a city might well do away with many of its air conditioners. In so doing, the citizens of that city would not only cut the energy use of their air conditioners, they’d essentially eliminate the need to generate perhaps 10 times that amount of energy in the first place. Make enough buildings cooler, get rid of enough air conditioners, and cascading energy savings mean pretty soon you’re closing down coal plants.

The power of cities

Cities offer the leverage for these sorts of changes. National and international standards and policies matter, of course, but the vast majority of decisions on things like building standards, urban design, and infrastructure are made at the local level. Cities are where demand reduction happens.

And many of the opportunities to cut energy use are mutually reinforcing, meaning that the more of them our cities pursue at the same time, the more affordable big shifts in energy use become. (Combine the synergies of these urban solutions with the fact that energy prices are predicted to become a major drag on urban economies, and big energy-use reductions not only become feasible, they show themselves to be engines of economic growth.)

Instead of achieving emissions cuts by trying to build wind turbines that outcompete coal plants (on a political playing field tilted against them), these cities eliminate our need for coal plants to begin with. We’ll still need a lot of wind turbines. But supplying clean energy to cities that use a small fraction of the energy they do today is a much cheaper and more achievable goal than trying swap the entire power system with clean alternatives.

The ability to drop energy demand and meet that lower demand with realistically deployable clean energy makes carbon-zero cities possible. If a city can reduce its energy use by 90 percent, covering the remaining 10 percent with clean energy is an entirely achievable task (and one amenable to a “local energy” approach). Balancing the remaining (non-fossil-fuel) emissions with ecological restoration efforts that soak up CO2 would then result in a carbon zero city — a city that in effect produced no net greenhouse-gas emissions at all. Indeed, carbon zero cities could over time become climate-repairing cities, their actions drawing more greenhouse gases out of the atmosphere than they emit.

If we build them right, carbon zero cities will outshine the cities we live in today. The idea that high energy use equates high quality of life is an outdated 20th-century one. People will live better in carbon zero cities, in part because of their lower energy use. Communities will be more vibrant and healthier; streets will more walkable and safer; local businesses will thrive; entrepreneurial opportunities will increase; and neighborhoods will be better prepared to survive hard times, whether those hard times come in the form of storm surges or skyrocketing oil prices. We’ll be thankful we acted while there still was time. Our kids and grandkids will be even more grateful.

So, climate change is likely unsolvable as an energy problem, but it looks entirely solvable as a cities problem. What follows is my best educated guess at what a workable set of such urban climate solutions might be.

Read on: Urbanism: Why good walksheds mean lower emissions

A footprint, of course, is the measurement of the total impacts of a thing, be it a building, business, or ballgame. Consumption, of course, describes the things we use. So consumption-based footprinting is an attempt to measure the total impacts of everything we use. Boiled down: If we use it, its emissions are ours, no matter where the thing originated.

Now, footprinting is a bit of an arcane art. Because cities themselves are brain-boggling in their complexity, modeling the kinds and amounts of greenhouse gases their economies create represents a considerable task. It is not an impossible task, however, especially if what we’re seeking is a model good enough to guide decision-making, not a perfect reflection of reality.

In order to get our “good-enough” model, we need to know what it is we’re trying to measure — and this is where the disagreements really begin. Essentially, there are three camps, which we might think of as city-map footprinting, mailbox footprinting, and shopping-basket footprinting (though their technical descriptions are often geographic, production, and consumption footprinting, respectively).

The city-map footprinters generally say we should measure those emissions created within a city, or created to directly power activities within a city: the oil burned in the cars we drive, the gas burned in our hot-water heaters, the coal burned in a nearby power plant to electrify the garage door, that sort of thing. This is the most common approach to footprinting, but its virtue is simplicity rather than accuracy.

The mailbox footprinters say we should measure all the emissions we ourselves produce. In other words, yes, we should include our cars, water heaters, and garage doors, but also the emissions our factories and workplaces create in the process of making the goods and services we export. This is a less common approach.

The shopping-basket footprinters say we should count all the emissions created by the things we use and consume, or created by the systems that support those things. So, yes, we should count our cars, water heaters, and garage doors, but also the roads on which those cars drive, the manufacturing plants that made those water heaters, and the mining and shipping operations that produced the coal burned to raise and lower those garage doors. Basically, this consumption-based approach says that if we use something and benefit from its use, we are responsible for all of the greenhouse gases it took to make that thing.

Even this can seem a bit complex, though, so I like to imagine that carbon emissions are cakes, and emissions-reductions are a diet. If we think of cakes and diets, we see that the three approaches like to count very different calories:

• Geographic footprinters say, “I will count only those cakes I both bake and eat at home.”
• Production footprinters say, “I will count all the cakes I bake, whether I eat them or not.”
• Consumption footprinters say, “I will count all the cakes I eat, no matter who bakes them.”

If what we care about is modifying our caloric intake (read: greenhouse gases), consumption-based footprinting is clearly the best approach. (For ethical reasons, we may also want to take a hard look at the kind and number of cakes we’re baking and sending elsewhere, but if we’re looking to lose weight … well, baker, heal thyself.)

Consumption-based footprinting helps us imagine carbon zero cities, because it gives us a truer sense of our climate impacts. In addition, it draws our attention to big systems. Looking at our lives, we begin to realize that large percentages of the greenhouse gases created in the process of housing ourselves, feeding ourselves, shopping, working, and getting around are emitted out of our sight or within systems not immediately amenable to change by individuals. We have a lot of work to do, and we cannot reach our emissions goals simply by tweaking the end product in a system — because most of our emissions come from the inner workings of the systems themselves.

This kind of understanding can be overwhelming, but also empowering: If we can see the systems that underpin our various ways of living, we can see, too, how changing those systems can produce large reductions in emissions patterns. Every city will be different, of course, having differently shaped carbon footprints and thus different systems-change priorities. But every city can use consumption-based footprinting to see its climate impacts more clearly and completely.

Back to Carbon Zero, chapter 1
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Forewarned

On Monday the 29th of October, 2012, a tidal surge 13.9 feet high (the highest ever recorded) washed up and over the waterfront in Lower Manhattan, pushed forward by the superstorm Sandy. That same week, the storm destroyed large swathes of coastline from the New Jersey shore to Fire Island, while driving torrential rains, heavy snows, and powerful winds inland across the eastern U.S. and Canada. By the time the storm blew out, it had killed more than 100 Americans, made thousands homeless, left millions without power, and caused at least $50 billion in damage. Sandy was, by any reckoning, one of the worst natural disasters in American history.

Maybe, though, the word “natural” belongs in quotes. Because what was surprising about Sandy wasn’t that it happened (indeed, many had predicted that rising sea levels and storms intensified by warmer oceans would make something like Sandy inevitable), but that it was seen so clearly, and so immediately, for what it was: a forewarning of what a planet in climate chaos has in store for us.

Sandy was far from the first sign that climate change is here — scientists have been warning for decades of the dangers of a heating planet, and in the last 10 years we’ve seen a flurry of unprecedented storms, droughts, floods, melting glaciers, and wildfires, as well as record-breaking heat waves following one after another. Sandy, though, knocked down walls of denial and inattention that have kept us from admitting what’s happening to our world.

What’s happening is that we’re losing the climate fight. Climate change is here, it’s worsening quickly, its effects are more dire than many thought they would be, and — if we continue with business as usual — we’re on a track to unleash an almost unimaginable catastrophe on ourselves, our children, and our descendants.

“Part of learning from [Sandy] is the recognition that climate change is a reality,” said New York Gov. Andrew Cuomo at the time. “Extreme weather is a reality. It is a reality that we are vulnerable.” He added later, ”Anyone who says there is not a dramatic change in weather patterns is denying reality.”

Our choice: “extremely dangerous” or “catastrophic”

To not warm the planet at all no longer remains an option. The Earth is already dangerously hotter than it was before the Industrial Revolution.

We used to think that warming up to 2 degrees C fell within a sort of “safe zone,” where we could expect change but not crisis. But in a world we’ve warmed only by about 1 degree C above the historical baseline, we’re already seeing massive climate impacts across the planet. These unexpected impacts, along with new projections from ever-improving climate models, tell us that the climate is not nearly as forgiving as we’d like it to be. As the Tyndall Center for Climate Change Research’s Kevin Anderson puts it, “1 degree is the new 2 degrees.” Two degrees, meanwhile, now appears not just dangerous, but extremely dangerous.

That means the menu of choices in front of us no longer includes a completely safe and stable climate. Instead, our choices come down to two options: a world in which climate change becomes extremely dangerous, or one in which it becomes totally catastrophic.

To keep climate change within that merely “extremely dangerous” range, scientists say, we must limit the rise in global temperatures to 2 degrees C. Allowing warming to accelerate beyond 2 degrees C to 4 degrees C takes us beyond extremely dangerous into downright insane.

Yet that’s where our current emissions trajectory is leading us: to a world 4 degrees C hotter, perhaps as soon as 2050; and perhaps even 6 degrees C hotter by the end of the century. Four degrees global temperature rise involves so many utterly catastrophic impacts — permanent droughts, large-scale shifts in agriculture, megastorms, rapid sea-level rise, ecosystem collapses, and so on (all triggering social instabilities) — that we can’t expect our global civilization to avoid serious disruptions, and in many places, long-term ruin. A world 4 degrees C hotter is, as some put it, “beyond adaption.” (A world 6 degrees C hotter is almost beyond comprehension: To conceive of a world 6 degrees warmer, imagine alligators in the Arctic.)

A world that’s 4 degrees C hotter would also be vulnerable to nonlinear climate feedbacks — ways in which the effects of warming (like the melting of the Arctic permafrost) could rapidly worsen warming itself (by, in this case, releasing enormous volumes of CO2 and methane now trapped in frozen soils). Some worry these feedbacks could lead to “runaway” climate change, wherein a cycle of warming and greenhouse-gas releases and more warming spirals viciously out of control. At that point, even the wildest “geoengineering” ideas — for example, creating artificial volcanoes to fill the stratosphere with sulfate particles, blocking some of the sunshine headed towards Earth — would be, at best, “Hail Mary” strategies (and would do nothing to address other catastrophic effects of rising emissions, like the acidification of the oceans and the resulting mass die-offs of ocean life). Spiraling climate chaos of this severity would leave us on a profoundly different planet than the Earth we now call home.

There is simply no way to put a cost to those kinds of impacts: Their magnitude transcends economic reckoning, because their impact could be greater than the entire human economy is worth. Four degrees of warming, Anderson and many others say, is therefore something we should avoid literally at all costs, because no economic cost we pay will be greater than the losses we risk in a climate catastrophe of that magnitude.

Now, all of this is the sort of thing that can bum you right the hell out, and it’s not irrational to let it get to you — there’s a real chance we may destroy civilization and much of the natural world in the decades ahead, and that’s a valid reason for being a bit glum. There’s just no shiny side to extreme climate chaos.

It’s not too late to avoid catastrophe

If that were the end of the story we could all just start drinking now. Hell, I’d buy the first round. But it’s not. We still have a choice. We still, just barely, have the option of choosing to limit warming to 2 degrees and then working hard to restore the climate once we’ve stabilized it. We can, yet, pause at “extremely dangerous” and pull back from the brink of chaos.

To do that, we have to limit the total amount of carbon dioxide and other greenhouse gases in the atmosphere. What’s the limit? Drawing on the scientific consensus, 350.org, the world’s leading climate advocacy network, puts the number at 565 more gigatons of CO2 (or about 450 parts-per-million [ppm] of CO2 in the atmosphere). That’s the most humanity can emit and still, probably, hold global warming to 2 degrees C.

That means we need to face a fact almost no one likes to discuss: We need to hit zero. That is, we need, as a species, to bring our global climate emissions into balance with what nature can safely absorb (actually, because we need to start rolling greenhouse gas concentrations backwards, we almost certainly need to emit less than nature can absorb, in order to take CO2 back out of the atmosphere and get back to safer greenhouse gas levels, of 350 ppm or less — but one shocking reality at a time is enough). This means that all the expressions of commitment we’ve heard from politicians about reducing greenhouse gas emissions by 50 percent off 1990 levels, say, or 80 percent by 2050 or whatever — all of those numbers are meaningless. The meaningful number is simple: zero, as soon as possible.

Zero, worldwide

A worldwide transition to a climate-balanced global economy (one which adds zero CO2 each year to the total CO2 in the atmosphere) lies completely within our reach. But to achieve it, we’ll need to be honest with ourselves about geopolitics and reality. Because we have some tough decisions to make.

Climate change is global, with people everywhere worsening the crisis. But we are not all equally responsible for the crisis we face now. Those of us who live in the wealthier nations got our wealth by cutting down forests, and burning coal and oil to fuel our industrialization. We are wealthy, to be blunt, because we’re the ones who put most of the greenhouse gases up there in the first place.

In the last century, to get wealthier, you needed smokestacks and clearcuts and coal mines. Poorer nations — whose economies rely more on older, more polluting technologies — argue that they have a right to grow their economies to help their people escape poverty and achieve prosperity. These nations are mostly willing to negotiate with wealthier countries on lowering their climate emissions rapidly, but they will need time to transition to low-carbon economies, and they expect that we in the wealthier countries will lead the way on cutting emissions rapidly to buy them time. Essentially, the poorer nations are saying, they have a right to the lion’s share of those remaining 565 gigatons of CO2.

Even ambitious plans for global emissions reductions take time. Poorer countries now emit less overall, but their economies are inefficient and largely dependent on dirty energy. Lots of work will need to be done for those countries to level off their emissions, and more work after that for their economies to become carbon neutral, even with really aggressive innovation — innovation bolder than any we have seen anywhere in the developing world. For example, one recent credible scenario by Kevin Anderson and Alice Bows would have emissions in poorer countries leveling off in 2025, then declining 7 percent per year thereafter, until the global carbon balance was restored. Seven percent a year, it should be noted, would be extremely bold: but even that extremely bold goal would demand that the wealthier countries buy time by zeroing out their own emissions first. The poorer countries argue this is a matter of “climate equity.”

Since we need their agreement, and their action, it’s probably smart to just go ahead and admit they’re right. It would be unjust to ask the world’s poor countries to absorb the costs of taking actions we ourselves avoid, in order to solve a problem we mostly created. We need to go first in zeroing-out our emissions.

But here’s the thing: far from being some unbearable burden, rapid reductions to net-zero emissions may in fact offer wealthier nations our best opportunity to rebuild our economies to prosper in the 21st century. To understand why, we need to look at the kind of planet we’re becoming: an urban planet.

Our urban future

Humanity is already an urban species, with more people living in cities than in the countryside. By the middle of the century, we will likely have as many as 9.5 billion people living on the planet, with 70-75 percent of us (around 7 billion people), demographers estimate, living in cities themselves, and 95 percent or more of humanity living within a day’s travel of a city. By the 2050s, the overwhelming majority of humanity will be participating in urban systems of health care, education, communication, commerce, and government that only a few decades ago were limited to the “developed” world.

Growth is transforming the very nature of cities. Every day, at least 200,000 people move to cities or are born in them. That’s like building a city the size of San Francisco every four days. Then doing it again, four days later. Then doing it again — and repeating the process several thousand times in the next 40 years. By 2050, we will have an estimated 3.5 billion more urbanites, and to house them we will have built a constellation of thousands of large cities, including a scattering of extremely large megacities, each home to tens of millions of people. The largest city-building boom in human history will happen in the next four decades, with each decade experiencing more change than the one before.

This urban boom won’t be wonderful for everyone; for many, it may be tragic. Unless we change our priorities quickly, as many as a billion people — climate refugees, the rural and destitute, victims of conflict and deep structural poverty — will live on the very edge of existence. Perhaps as many as 3 billion people will live in informal settlements — in the huge slums springing up around many developing world cities. Hundreds of millions of these slum-dwellers will live in abject poverty. Inequalities will strain our societies. In the midst of widespread poverty, 3 or 4 billion others may rise out of poverty to enter the global middle class, living what we today would consider a “modern” — if modest — life. A billion may well live in even greater affluence than we experience today. And the one thing the vast majority of these people will have in common is their cities, and the ways in which those cities are linked together.

How we build this coming wave of cities will largely decide not only the quality of life of the people living in them, but also the future of our planet. Because how we build our cities will decide, more than any other factor, how much we heat the planet.

Our urban opportunity

Climate emissions are a byproduct of the global economy; but the links that connect that economy together are forged in our great cities. In this book, we’ll see how the choices cities make about how they grow will largely determine whether their economies will be clean or dirty; and the choices these cities make, in aggregate, will largely determine whether the global economy as a whole will be catastrophic or full of possibilities.

In 40 years, humanity will live in thousands of these major cities, each stamping the global economy with its own character — and burdening the planet with its consumption and pollution, to greater or lesser degrees. But right now, the economies of only about 200 cities define the global economy. These cities and the regions surrounding them are responsible for the vast majority of their countries’ prosperity, and also of their countries’ greenhouse gases.

Most of these cities are still in the wealthier nations. If our cities reinvent themselves, finding pathways to low-to-no-carbon futures, our nations can rapidly cut climate pollution, even if most of our compatriots lag behind in reducing emissions. Building cities that produce no net emissions — that reduce emissions to the extent that the greenhouse gases generated can be balanced through other actions that draw CO2 out of the atmosphere (what I call “carbon zero” cities) — may in fact be the smartest, quickest pathway to lowering national emissions.

Furthermore, the options that will be available to those thousands of emerging cities over the next 40 years largely depend on the choices we in the world’s wealthiest cities make today. The reason is that innovation and invention move slowly, yet are critical. When no new solution is available, business as usual is a given. Once a better solution to a given problem has been found, its spread can be hastened, though innovation diffusion still takes time. As the wealthier cities design away their own emissions, many excellent new solutions will be created, resulting in zero-emissions pathways poorer cities will be able to follow as they get wealthier.

There’s no time to lose. The costs of action will rise, not fall, with time. Many big investments have long life spans: They can operate for decades — and need to, in order to pay back the costs of their construction. This makes it politically very hard (and sometimes economically expensive) to shut down new infrastructure and industrial systems, even when those systems are producing unwanted results. What we build in the next two decades will probably be with us for decades more. Making new investments in old, dirty ways of doing things (like coal-fired power plants, highways, and suburban sprawl) retards change, and commits us either to continued pollution or to costly retrofits and replacements in the near future. But also, the longer we wait, the more the consequences of climate change already set in motion will hamper our progress and make us less able to act. All of the impacts of climate change have human costs, in many cases quite large. Few have any benefit at all. The longer we wait, the more our economic capacity for change will be damaged by droughts and floods, rising oceans and spreading diseases, climate refugees, and political instability. This is not even to mention the increasingly heart-wrenching human costs or the psychological trauma caused. Sandy was just a taste of what climate change could cost us.

Our cities as climate solutions

So, changing how our cities work proves to be a pretty vital job. Fortunately, our comparatively massive wealth has left us with a number of capacities the rest of the world simply doesn’t have: The majority of the world’s research universities, think tanks, engineering and design firms, advocacy groups, investment funds, venture capitalists, and so on, are all concentrated in the wealthiest cities — and even with China, India, and Brazil growing by leaps and bounds, this central fact of the concentration of the capacity for innovation in a relatively small number of rich cities is unlikely to change overnight.

Leading the way into a carbon zero future will be good for business. Cities that innovate in design, planning, policy, and products will equip their citizens with exportable skills and marketable experience before those in slower cities even know they exist. With thousands of large and small cities about to boom, the markets for urban innovations are almost inconceivably vast. There’s a 40-year boom on its way; cities that lead the way into a carbon zero future will be its great success stories.

Many of the most important kinds of innovations, policies, and plans needed to create such urban success stories are local — or are, at least, the kinds that don’t demand bold national action to succeed. In countries like the United States, where dirty energy companies have managed to clog the works of government, the ability to innovate meaningfully at a local level represents a huge advantage. Our major cities are small enough that committed people can actually change them, and large enough that changing them can produce big impacts.

Americans, Canadians, and Australians, in particular, sail now on a collision course with planetary realities. Our sprawling suburbs and low-density cities depend on abundant resources, cheap oil, and low costs for pollution, none of which the future holds. No amount of political grandstanding will change that fact. Sprawling, auto-dependent suburbs are unsustainable, and that which cannot be sustained does not long continue. For the size of their populations, our cities are the most climate-damaging in the world.

Even Northern European cities, with their older, more compact urban forms, better transit, and reputations for climate leadership, are far from sustainable — they, too, need a lot of change — but I have chosen to focus on North American cities precisely because that is where we need the biggest change in the shortest time. (Readers from the rest of the world should find a few ideas worth mulling over — much of what applies to North America applies without too much translation to Australia and New Zealand, as well as in parts to much of Europe and the prosperous parts of Asia, especially Japan and Korea. Around the world, leadership will take different forms: the imperative to lead will be the same.)

I’m writing most directly to my fellow Americans, though. That’s because I care deeply about my country, as do most Americans. I believe that if we truly love our country, we must care about its future; and we can’t care about its future without taking into account the ways our nation’s actions today are shaping that future; without attempting to steer a course that will leave our countrymen better off in the future. To love our country today is also to wish to see it secure and prosperous tomorrow. So to be patriots, we have to want to be good ancestors to those who are coming after us. And being good ancestors today means, perhaps above all else, fighting climate change. No greater threat faces America in the coming years than climate chaos. We learned that with Katrina; we’ve learned that with droughts and floods and wildfires; and now we’re learning it afresh as our nation recovers from the assault of a superstorm of unprecedented size. And the biggest storms are still ahead.

Building carbon zero cities means not only greater prosperity, but more security. Almost everything we need to do to drop our climate emissions also leaves us more rugged and resilient to disasters and global instability. Carbon zero cities mean future-proof cities, or as close as we’re likely to get.

Our choice could not be clearer, to my mind: Remake our cities into central hubs in the global climate-neutral economy we’re moving towards (and ready ourselves for the tough times to come), or shirk our responsibilities and leave ourselves even more vulnerable to the onrushing chaos. As a patriot, the right choice for America is plain to me.

Imagining carbon zero cities

How do we get to work? Well, we can’t build what we can’t imagine, so the first task in building carbon zero cities is to reimagine the cities we have.

Reimagining is hard work. It requires both a robust conversation about what carbon zero cities might be like, and a far more creative approach to envisioning the kinds of innovations and solutions that could get us there. This little book is my attempt to outline one version of a carbon-neutral city; to get a conversation going about what kind of change a 90 percent cut in emissions might entail; and to point out some of the main areas of possible innovation.

It’s worth emphasizing that this is a sketch, not a blueprint. I wouldn’t even attempt to ordain a model for zero-carbon development that every place should adopt. Every city is unique, with its own character, geography, civic culture, and history. Regional economies and politics have left every metro area with different workforces, institutions, and business cultures. The implementation of national policies and local capacities vary widely. No one set of innovations applied in a specific way will suit the needs of every city. Large teams of professionals and engaged citizens should (and I hope, will) take up the actual work of upgrading their cities. I’m not interested in dictating approaches to anyone.

Indeed, it seems to me that what we need most right now are not conclusive answers, but good hypotheses put immediately to the test; and good hypotheses spring first from reframing our understanding of a given challenge. I hope that my reframing of this challenge will influence readers to begin to see their own cities’ challenges in a new light.

But don’t expect things to look normal, illuminated by the demands of the future. We have, again and again, mistaken what we think of as “normal” for “best” and “permanent.” Normal as we knew it in the second half of the 20th century is already a thing of the past. Already, many of our older systems are crumbling, revealing themselves to be unsustainably expensive or indefensibly harmful. Even the timescales of the 20th century are out of date. Changes that took half a century before are erupting in a few years now.

The speed of change will not slow. It is both pulled along by the dire necessity of quick action — for, as Donella Meadows has written, on a planet full of limits, “Time is in fact the ultimate limit” — and driven along by the unleashing of innovation, collaboration, and competition on a planetary scale that dwarfs anything our great-grandparents could have comprehended. If the ultimate limit turns out to be time, the last infinite resource turns out to be creativity.

I believe that planetary limits and human creativity are now inextricably bound together. I doubt we’ll reinvent the physical limits of this world, at least in the next few centuries. I would bet against the emergence of any technologies that allow us to exceed our planetary boundaries on both a global scale and a sustained basis. But I would also bet we can build a civilization that works within our planetary limits, and furthermore, that the realm of possibilities for human experience within those ecological limits is essentially infinite.

Indeed, as we cease trying to maximize the volume of material growth and start emphasizing sustainable prosperity, I think we’ll find that what we’re able to do with energy and materials becomes more and more brilliant, meaningful, and enriching. Design constraints often deliver better results than a belief in complete freedom. Quite the opposite of imposing hardship, carbon zero targets may very well spur a renaissance in urban creativity.

The straining limits that pressure us to remake our cities will likely produce an unprecedented blooming of applied creativity and civic acumen. I find it completely likely that the constraints of climate neutrality and ecological sustainability, boldly met, may produce the most livable, prosperous, and resilient cities the world has ever seen.

Nothing in this book is utopian: Most of what I suggest is already being implemented or experimented with somewhere, though no city I know of has put all the pieces together in one place. Some of what I suggest still lives in the realm of conjecture, but that realm is not as far away as it used to be.

I hope you will take my sketch, use what makes sense to you, discard what doesn’t, and begin your own drawings of what the future’s possibilities can be — they are bound to be better than mine, and the world needs every well-grounded, well-crafted vision it can get. Please, don’t just read: reimagine.

Read the sidebar to this chapter: Consumption-based footprinting.

Read on: Why clean energy isn’t enough