Often, the first step to helping people make better choices is showing them that there are choices.

One of the biggest and most important -- albeit frequently overlooked -- steps toward combating global warming, improving public health, reducing air pollution, and restoring a sense of community and fellow-feeling to American life is changing the structure of our communities.

Right now, conventional wisdom is that the choice is between suburbs -- big houses, plenty of privacy and safety, big, cheap retail readily available -- and tight, cramped, dangerous, dirty living in a city, with corner stores the only source of provisions. This perception is off, but it's not that far off. There are still too few concrete examples of dense, safe, mixed-use walkable communities with all the conveniences of the suburbs.

So, forthwith, Dave's Two-Step Plan for Cleaner, Safer Communities:

1. Show people the costs of the suburbs. A pair of just-released studies show that people in less-walkable, less-dense areas (read: suburbs) are more likely to suffer from obesity and air pollution. Don't demonize people for living in suburbia. Don't mock or deride them. Just make the consequences of the choice as clear and widely known as possible. Make the invisible visible.

2. More importantly: Find better communities. If you can't find them, design and build them. Talk about them. Publicize them. And -- are you listening, all you enviros? -- if at all possible, live in them. Right now, it's difficult: difficult to find them, to afford living there, to get a nearby job, etc. But we can't very well browbeat other people to abandon the suburbs if we don't. Only a steady and rising tide of demand will cause more such communities to develop. People will only abandon unhealthy ways of living when they can see and touch and visualize healthy ways of living. Real, viable alternatives do more than any amount of debate or persuasion. (Exhibit A: The Prius)

Is your living situation healthy and energy-efficient? Do you know of walkable communities in your area? Tell us about them in comments.