“Accommodating wildlife in cities doesn’t necessarily require massive investment” says Susannah Lerman, a University of Massachusetts ornithologist. But as author Richard Conniff points out in his article in Yale University environment 360 blog you have to know what to do. “Curiously researchers have barely begun to think about what wildlife already lives in the city, or how to encourage more of it.” In 2009 Douglas Tallamy, a University of Delaware entomologist, published a ranking of trees and shrubs according to how many caterpillar species they harbour, which is a good starting point to look into biodiversity.

In the U.S. Mid-Atlantic state Maryland the Baltimore County examined street trees. Recent research has shown that oaks benefit everything from caterpillars to songbirds. Even fish prosper, because the aquatic invertebrates they feed on favour oak leaves on stream bottoms. And oaks accommodate 537 species of caterpillars , says researcher Tallamy. Gingkoes, a standard street tree in many cities there, host just three.