We are marching towards a future in which three-quarters of humans live in cities, more than half of the landmass of the planet is urbanized, and the rest is covered by farms,pasture, and plantations. Increasingly, as we become ever more city-centric, species and ecosystems crafted by millions of years of evolution teeter on the brink of extinction - or have already disappeared. A growing band of 'urban ecologists' is beginning to realize that natural selection is not so easily stopped. They are finding that more and more plants and animals are adopting new ways of living in the seemingly hostile environments of asphalt and steel that we