THE discovery of a new ecosystem, a deep-sea hydrothermal vent, say, is a rare and exciting event, and tends to be big news. But one of the biggest “discoveries” of recent years is going on quietly, right under our noses. It turns out that cities – those noisy, smelly, garbage-strewn expanses of asphalt and concrete – are vigorous ecosystems in their own right.
Of course, we have always known that cities are home to more than just us humans; ask anyone with a backyard bird-feeder or a plague of mice in their kitchen. But, as ecologists are learning, cities are not just accidental homes for animals that really ought to be elsewhere. They are also hotbeds of evolutionary change, shaping the adaptations of their resident fauna as surely as the Serengeti plains or the Amazon rainforest (see “Evolution gets busy in the urban lab”).
Nor are cities merely lower-quality versions of some idealised natural state. Like any other habitat, they offer animals both advantages and disadvantages. Squirrels in suburban Chicago, for example, feast on a plentiful summertime smorgasbord, courtesy of overflowing garbage cans, bird-feeders and picnic leftovers. This is far beyond the dreams of their wild-land cousins. But they pay for this summertime bounty once the snow starts to fall because they cannot stash away sunflower seeds or crusts of bread for the winter the way forest squirrels hoard acorns. The result? The city’s squirrels get increasingly desperate for food and aggressive as winter progresses.
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As we begin to view our cities as worthwhile ecosystems, we may begin to ask questions that ecologists and urban planners have largely ignored until now. How can we make our parks and gardens hospitable to a wider diversity of species? How much green space do we need, and in what configuration? What would it take to bring new birds or insects into our cities? Can we establish new predators in urban ecosystems, such as dragonflies, hawks or coyotes, to help us control some of the less desirable pest species, or will they become pests themselves, as urban foxes have? Researchers have a lot to learn about the ecosystem most of us live in. As cities become more dominant and wild lands recede, this knowledge will become increasingly important.
“Discovery” of the urban ecosystem has another big benefit: it brings ecology up close and personal. No longer is the natural world something “out there” in national parks and wildernesses. City dwellers might be only mildly interested in tropical rainforests, but they connect emotionally to the squirrels and sparrows they see every day. In a world where nature needs all the friends it can get, that can only be a good thing.
