I’ve been studying the growth of U.S. cities from 1990 to 2000, trying to get a handle on how much habitat was lost to urban sprawl.
When most people think of sprawl destroying natural habitat, they think of a big, fast growing city. Sure enough, if you look at the total number of acres lost, the names at the top of the list are places like Atlanta, Phoenix and Las Vegas.
If you stop to think about it, though, that’s a bit unfair, because these cities have to house a lot of new residents. If you calculate acres of habitat per new resident, a whole new set of names come to the top of the list, places like Duluth, MN, and Johnstown, PA. Some cities even lose population and still lose habitat.
Another concept I’ve been exploring is what I’m calling sprawl inequality. This comes out of the famous Pareto Principle, that 80 percent of any phenomenon is due to 20 percent of the people. How much of habitat loss in cities is due to a small proportion of folks living in suburbs or exurbs? After a bunch of GIS work, the answer appears to be: 80 percent of urban development (in terms of area) is due to 35 percent of folks who live at the lowest densities. We may all have a responsibility to move toward more sustainable cities, but we aren’t all equally to blame for sprawl.
These kind of statistics about urban form are important because (among other things) the shape of our cities affects how much energy we use, and hence how bad global warming will be. The Obama administration has hinted recently that it will try to change federal transportation and urban development so they help us meet our goal of preventing climate change rather than hurting our progress toward that goal (see, for example, thw Washington Post‘s Juliet Eilperin’s reporting on the planning meetings on climate change strategy that include HUD and the Department of Transportation).
It’s a logical idea that will inevitably be opposed by some folks on Capitol Hill and K Street. Quite apart from that political battle, I’m interested in a theoretical question. Has anyone looked at climate change inequality in the United States? What proportion of high-emitting Americans is responsible for 80 percent of greenhouse gas emissions?
It is also comical to me how tardy my research is. The National Land Cover Database for 2000 wasn’t completely finished until a couple years ago, which slowed my research down. And even now I’m being coy with my results because I don’t want to violate my copyright agreement with the journal that publishes this research. So I’m presenting national statistics on urban growth that are almost a decade old, when a great deal has changed in the past two years. The rapid rise in oil prices has changed how people commute, and the collapse of the housing bubble has temporarily stopped construction in many far suburbs. At this point, 2000 seems like ancient history.