We talk a lot about chain stores and the way their proliferation takes away the individual character of American cities, replacing it with a homogenized urban landscape of Wal-Marts, malls, and Applebees*. But some scientists think businesses and buildings aren't the only thing making our cities look more alike.
The ecology of cities could be homogenizing, as well — everything from the plants that grow there, to the number and density of ponds and creeks, to the bacteria and fungi that live in the soils. My newest column for The New York Times Magazine explains why ecologists think cities are becoming more alike, and what it means if they're right. The really interesting bit: The effects aren't all uniformly bad.
"Americans just have some certain preferences for the way residential settlements ought to look," Peter Groffman, a microbial ecologist with the Cary Institute of Ecosystem Studies in Millbrook, N.Y., recently told me. Over the course of the last century, we've developed those preferences and started applying them to a wide variety of natural landscapes, shifting all places — whether desert, forest or prairie — closer to the norm. Since the 1950s, for example, Phoenix has been remade into a much wetter place that more closely resembles the pond-dotted ecosystem of the Northeast. Sharon Hall, an associate professor in the School of Life Sciences at Arizona State University, said, "The Phoenix metro area contains on the order of 1,000 lakes today, when previously there were none." Meanwhile, naturally moist Minneapolis is becoming drier as developers fill in wetlands.
Why does any of this matter to anyone who's not an urban ecologist? "If 20 percent of urban areas are covered with impervious surfaces," says Groffman, "then that also means that 80 percent is natural surface." Whatever is going on in that 80 percent of the country's urban space — as Groffman puts it, "the natural processes happening in neighborhoods" — has a large, cumulative ecological effect.
*Or, possibly, Applebeeses.