They really are concrete jungles! Why you’ll never think about cities the same way again

Of course, it’s also true that in the world of birds and plants, as in human society, there is such a thing as a cosmopolitan – the city-dweller who feels equally at home in San Francisco, Milan and Beijing. Four birds occur in more than 80 percent of the cities studied, and 11 plants occurred in more than 90 percent of the cities. On the plant side, those include phragmites, meadow grass, shepherd’s-purse; weeds, all of them, and seemingly spread by European colonization. In the air, it’s the usual suspects: the rock pigeon, the house sparrow, the barn swallow and the European starling. “These four have become completely adapted to urban life,” Katti says. “That’s not much of a surprise. But they don’t actually dominate as much as we think they do.” Those species — representing the closest thing we have to a pan-urban bio-profile, occurring in cities across the globe — represent only a small fraction of a city’s natural diversity. Invasive species have not conquered metropolitan ecology.

Not all cities are equal stewards of native flora and fauna, though. One of the biggest predictors for a city’s biodiversity is its urban design. Territory as varied as backyards, street trees and highway medians can play important roles in greening a city. In fact, the amount of green space is a stronger predictor of the density of biodiversity than a city’s size. A metropolis with a sizable network of parks can contain more species per square mile than a much smaller but more compact city.

That finding endows urban designers with power and responsibility, and makes Katti feel optimistic. “Our data show that even cities which are never built with biodiversity conservation in mind still provide habitat for a fair number of native species, including endangered species,” he says. “It’s true for birds, it’s true for plants, it’s true for mammals — coyotes or foxes in California, primates in tropical cities in Asia and Africa. Even though nobody built with green design in mind until recently, cities provide habitat for so many species. Imagine what we could do if we became more ecologically conscious in designing cities going forward.”

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