Dear Umbra,

I just took the Ecological Footprint Quiz, feeling rather confident that I’ve been doing my part to minimize my personal impact on environmental despoliation. But my results weren’t reassuring. My ecological footprint is nine acres, which is much better than the U.S. national average of 24 acres per person, but still twice what the planet could sustain. In short, the quiz tells me, if everyone lived like me, we would need two planets.

I’m not sure I can make any more big changes — I take public transportation when I can, I’ve kept my 10-year-old Honda, which still gets about 35 mpg, I’m vegetarian, I choose locally produced goods whenever possible. I don’t know what else I can do. After several years of effort to “live green,” am I still such a big part of the problem?

Despairing Amateur Green

Dearest Carrie,

Maybe we just need two planets. Maybe that’s the point of the ecological footprint quiz: to find out how many planets we need so that NASA can develop an appropriate space program.

How big is your footprint?

For those of you who haven’t taken the quiz, it’s an online survey about living habits. You answer multiple-choice questions, the computer tallies the result and tells you how many planets we would need if everyone lived like you, and then you feel guilty. Redefining Progress and Earth Day Network developed an elaborate calculator that incorporates complex country-based data into your responses, and the components of the calculator make it quite difficult to get a one-planet result (though I did it by cheating). In the United States, environmental impacts indirectly linked to your personal consumption are what put you on the two-planet program. You may drive very little, but because you’re an American, roads are still included in your footprint, as are the impacts of conventional agriculture and the military-industrial complex. The footprint gizmo calculates your impact within the context of your country.

Leaving you feeling hopeless is not the intent of the exercise. Instead you’re meant to be motivated to change your life and your community. Messages from environmental organizations can be confusing, and the Footprint Quiz may be guilty on this score.

We tend to focus on the impact of individual consumption habits on resource degradation and environmental destruction. Folks who heed this message may gradually become obsessed with their own actions as the crux of good and evil. Projects like the Footprint Calculator can encourage this mindset. While looking inward to examine our car mileage and food choices is, in aggregate, a powerful tool for harm reduction, it’s not the only thing that eco-conscious people can do to make a difference — and it’s also not the most important thing. An individual decision to drive less is vital, and it’s true that if all Americans reduced yearly mileage the world would be a better place. But simply opting out of driving yourself does not make for an improved mass-transit system or more walkable communities — for this we must become advocates.

The human population as a whole has outstripped the planet’s capacity by about 35 percent, according to Redefining Progress’s calculations. But until we find another planet, we’re stuck here, forced to work together. Instead of feeling guilty about your individual impact on the earth, band together with other concerned folks to fight for broader societal changes — a more sustainable system of agriculture, stronger open-space protections, real corporate responsibility, better environmental laws.

To finally answer your question, we are all part of the problem, but we are also the solution.