Many environmentalists celebrate the environmental benefits of densely developed urban centers. Urban living reduces the scope of humanity's footprint on the earth in many ways. Not only do cities fit more people on less land, but urban density generates tremendous economies of scale that lead to greater energy efficiency and other material savings. There are environmental costs of density, to be sure. Air pollution tends to be higher in more densely populated areas, and the concentrated pollution flowing from dense areas will, in some circumstances, be more likely to overwhelm nature's inherent absorptive capacities. Nonetheless, environmental activists have long championed dense urban growth over the dominant alternative of suburban sprawl.

Environmentalist gadfly Jeremy Rifkin challenges this consensus in today's Washington Post. Rifkin argues that urbanization, combined with population growth, comes at a terrible environmental toll; "our burgeoning population and urban way of life have been purchased at the expense of vast ecosystems and habitats."

The flip side of urbanization is what we are leaving behind on our way to a world of hundred-story office buildings, high-rise residences and landscapes of glass, cement, artificial light and electronic interconnectivity. It's no accident that as we celebrate the urbanization of the world, we are quickly approaching another historic watershed: the disappearance of the wild. Rising population; growing consumption of food, water and building materials; expanding road and rail transport; and urban sprawl continue to encroach on the remaining wild, pushing it to extinction.

I am not much of a Rifkin fan, largely due to his Luddite view of modern technology, and I don't entirely accept his analysis. Nonetheless, I think this article is worth a read.