Last summer, bird-watchers confirmed the discovery of a new species of bird in Cambodia was not an event of particular biological significance, but it was striking for one reason in part. This species of bird was discovered not in an unspoiled rain forest but within the limits Cambodia's capital, Phnom Penh – a city the size of Philadelphia.
What the researchers found was surprising in cities. The medium-sized city in the state about 110 species of birds, over 95 percent of which would have been growing there urbanization. Ecologically speaking, cities are different, concrete buildings. Rather, each unique bio-profile – a kind of ecological fingerprint – that is against the idea of an environment dead zone.
Of course, it's also true that in the world of birds and plants, as in human society, there is such a thing as worldwide—the city-inhabitants who feel 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 are seemingly spread by European settlement. In the air, it's the usual suspects: the rock pigeon and many other birds. “They have become completely adapted to urban life,”Katti says. “That's not much of surprise. But they don't actually dominate as much as we think they do.” Those species—occurring in the cities across the globe—represent only a small part of a city's natural varieties.
Not all cities are equal protectors of native animals and plants, though. One of the biggest predictors for a city's biodiversity is its urban design. Territory as varied as backyards and street trees can lay 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 city.
In a world where architecture, food, language, fashion and commerce are increasingly globalized, a city's native animals and plants can be a kind of identity. There may be neighborhoods in London and Paris that resemble Singapore or Hong Kong. Cities are becoming similar, but their natural environments stand completely apart.
