ecosystems

Yes, but probably not anytime soon. The Intergovernmental Panel on Climate Change estimates that the planet's average air temperature could warm by as much as 11.5°F by the end of the century. As a result, the world could be warmer than it was 55 million years ago, says Mark Lynas, author of Six Degrees, an analysis of hundreds of climate studies that reads like a nonfiction version of The Day after Tomorrow. Back then, the Canadian Arctic was as balmy as Florida and lousy with crocodile-like animals called champsosaurs.

If you feed the neighborhood stray cat, he'll keep coming back. He'll remember your house as an easy source of food and won't have to scavenge for as much garbage or chase down as many field mice. The same thing obviously applies to birds and bird feeders, just on a much larger scale. At that point—when hundreds of thousands, even millions of feeders are involved—what kind of effect does the feeding have on the animals' natural ecosystem? That's the question Gillian Robb and her team at Queen's University Belfast in the U.K. set out to answer through an experiment of their own and a review of the existing literature.