There is already a new field of urban ecology for scientists who study the city and biophysical interactions within it, in a similar way to traditional ecosystem research. In fact, a surprising amount of wildlife now depends on the human-made environment, from the clouds of huge Sydney fruit bats to London’s wily foxes, to skyscraper-nesting peregrine falcons, animals have made cities their home - in some cases, their natural habitats have disappeared. In other places, the mix of human-introduced plant and animal species, and those opportunists that migrate to the urban environment, are interacting to produce unique ecosystems that exist nowhere else. Seagulls, for example, now often live in cities hundreds of kilometres from the coast. As their traditional food – fish – becomes scarcer, they scavenge human rubbish.
Whether traditional conservationists and wildlife lovers learn to value these new flourishings that are occurring at such a rapid rate is still to be seen. But what is certain is that the survivors of these menagerie experiments in the human garden will produce a genetic legacy. In centuries to come, new species that could not have formed under pressure from any natural circumstances will be testimony to our mixing. Already, urban moths have evolved changes in shade suiting their dull concrete habitat (compared with the tree trunks they used to live among), songbirds have got louder to compete with traffic noise. And, as many city dwellers know, there are now new varieties of urban rat, housemouse and cockroach.