If the definition of insanity is making the same mistakes over and over, then many cities have taken a certifiable approach to securing their water supplies -- and they need some radical therapy before taking the big economic, ecological, and human hits that come with a permanent state of thirst.

That’s the conclusion from a new study in the journal Water Policy, whose authors compared the water supply histories of four cities -- San Diego, Phoenix, San Antonio, and Adelaide, Australia. Among the lessons learned? Urban water conservation, recycling, and desalination aren't silver bullets. In fact, the best solution may lie upstream with farmers -- saving just 5-10 percent of agricultural irrigation in upstream watersheds could satisfy a city’s entire water needs.

But the time to act is now, argues Brian Richter, a senior freshwater scientist at The Nature Conservancy and the study’s lead author -- he says a global urban water crisis is already here. Below, Richter tells us more about what cities need to do to say on the right side of dry.

Q. Many cities take a similar pattern of water development, according to your research -- going from exhausting local surface and groundwater supplies to importing water to implementing water conservation to finally recycling water or desalination. Why is this pattern unsustainable?

A. When we overuse a freshwater source, we set ourselves up for disaster. Each of the cities we reviewed in our study has contributed to the drying of a major river or important groundwater spring. That has obvious ecological impacts and social consequences -- it affects livelihoods and human health by compromising fish production, concentrating pollution, or curtailing recreational activities.

Our research is revealing that water scarcity also causes severe economic losses by limiting or disrupting agricultural, industrial, and energy production. Texas lost nearly $8 billion in agriculture last year due to water shortages; electricity generation from hydropower dams on the Colorado River in 2010 dropped by 20 percent due to water shortages. Some estimates suggest that China may be losing $39 billion each year due to crop damage and lessened industrial production, and hundreds of thousands of people around the globe are being forced to move due to water shortages.

Because these impacts are so pervasive and damaging, we need to begin investing in water supply approaches that don’t just minimize these adverse impacts but instead begin to reverse them.

Screenshot of Milwaukee's "greenness" measures vs. average home value by neighborhood. Source: City Nature

The evidence keeps sprouting up like daffodils: Experiencing nature is good for us -- physically, emotionally, cognitively. (Check out this new study on how a walk in the park can reduce brain fatigue.) But as the world becomes ever more urbanized, which urbanites have enough access to nature to reap these benefits … and how can we make that access more equitable?

Enter City Nature -- a new project from Stanford University that maps the “greenness” and “paved-ness” of more than 2,500 neighborhoods in 34 U.S. cities (as determined by the shade of remotely sensed pixels) and then lays over that demographic data such as ethnic diversity and average home value as well as access to parks to produce portraits of American urban nature -- who lacks it, who has it in abundance, and how those disparities match up with individual city plans and visions.

Those disparities are wide, according to Jon Christensen, an environmental historian who is one of City Nature’s two principal investigators and who teaches in UCLA’s History Department and Institute of the Environment and Sustainability. The hope, says Christensen, is that urban planners and activists can use City Nature’s data to eventually pinpoint the neighborhoods that have the greatest “nature need” -- and take action.

But City Nature’s data also holds surprises -- including how much urban nature in the United States has happened in spite of central planning, and how little impact great landscape architects such as Frederick Olmsted have had on that development. I caught up with Christensen to learn more:

Wood thrush. (Photo by Jeff Whitlock.)

Cross-posted from Cool Green Science.

Mercury pollution -- nothing to worry about if I don’t live in the rural Northeast and don’t eat tons of fish, right?

Guess again, says a new report done by the Biodiversity Research Institute (BRI) in conjunction with The Nature Conservancy. The report, "Hidden Risk," details the widespread and deep impacts of mercury pollution in terrestrial nature -- particularly on animals such as songbirds and bats. Researchers are discovering how mercury is causing big declines in reproductive success among these species, as well as physiological oddities -- like developmental asymmetries and an inability of some birds to hit high notes.

Photo: Scott PenaCross-posted from Cool Green Science. Let's say the rise in sea level that climate change will bring us -- from melting ice caps and expanding seas -- won't be "all that bad" by, oh, the year 2080. Maybe ... just half a meter (a little under 20 inches). We can deal with half a meter, right? Well, yeah -- if we're ready to "deal with" almost 50 percent more affected people and 73 percent more property losses from a typical Category 3 hurricane -- all because of the higher storm surge that'll come from that additional 20 inches of …

Joanne Wilson surveying coral reefs in Raja Ampat Cross-posted from Cool Green Science. You've probably heard about coral bleaching -- the mass die-off of coral reefs because of warming sea temperatures, a dynamic that can be attributed at least indirectly to climate change. It's a problem of growing concern to the hundreds of millions of people whose lives depend on reefs and the fish they shelter. But as ocean temps continue to rise, is there any hope for coral? Science to the rescue! Researchers are learning tons about which kinds of coral species are either resistant to bleaching or bleach more …

New York City's High Line Park. Nature is everywhere, if you know where to look.Photo: John Dalton.What’s more ecologically valuable -- national parks, or median strips and vacant lots? Could dreaded invasive species actually be more beneficial than native ones? Are environmentalists clinging to a timeless notion of nature that science has thoroughly discredited? Can we actually make nature better than it is in its "natural" state? Emma Marris asks these and other icon-busting questions her new book Rambunctious Garden -- potentially the most optimistic and controversial work about the future of nature to appear in years. Marris, a former …

Cross-posted from Cool Green Science. Want to know how climate change might affect a seashore near you? Look at what it's already done over the past 20 years to a stretch of the Florida Gulf Coast, according to a pathbreaking new study published in the journal Climatic Change. Sea-level rise along the Waccasassa Bay area (90 miles north of Tampa) is already picking winners and losers in nature there -- and the losers include the habitat the iconic Florida black bear and the bald eagle depend upon. People up and down Florida’s Gulf Coast might soon suffer, too, if sea-level …

Pistachios: What shell remain? Photo: PatternedCross-posted from Cool Green Science. What won't climate change affect? Well, cross trail mix and cherry pie off that ever-shrinking list. It turns out that crisp apples, chewy almonds, ripe plums, and a host of other nuts and stone fruits might become much more costly to grow -- or not grown at all in some spots -- because of rising winter temperatures, according to a new study published in the peer-reviewed journal PLoS One. The problem, say researchers: The trees that produce these goodies need a certain number of hours at cold temperatures -- or …

The helpful Jerusalem cricket.Photo: Franco FoliniCross-posted from Cool Green Science. There are 1 billion bacteria in a single gram of soil. (Give or take a few million.) But how can you get that army -- and its insect friends, like the two-inch Jerusalem cricket pictured to the right -- to help you grow bigger veggies and prettier flowers? There's nobody better to ask than Nature Conservancy soil ecologist Sophie Parker, who recently turned Grist on to the fascinating (and sometimes scary) world of soil organisms. I asked Sophie to give us some tips to make our gardens grow even better …

Photo: U.S. Fish & Wildlife Service -- Pacific RegionCoral reefs are in big trouble worldwide -- and that's not just bad news for snorkelers. It could mean death instead of life for millions of people ... maybe even you. Here's why: Coral already provides the elemental compounds for a growing number of crucial medicines and health products -- ranging from antiviral drugs like Ara-A and AZT to anti-inflammatories, painkillers, and even sunblocks. But science is in a race against time: We've just started to plumb the depths of coral's potential to attack the world's health issues ... only to have …