© Mark Goddard
While meadow grass and rock pigeons take the title of most cosmopolitan among plant and bird species, concrete jungles have caused big drops in species diversity overall.
Only 25 percent of native plant species and 8 percent of native bird species exist in city habitats compared with density counts of non-urban species. Land availability and cities' ages, along with other human-induced factors, best explain the species loss, scientists report February 12 in the Proceedings of the Royal Society B.
Despite the declines, cities still have native populations, which, if cultivated, could serve as starting point for conserving nonhuman urban natives, the authors say.