Global warming is changing the face of the planet, and a key panel estimates that a quarter of the world's species will die out—but a few organisms are already evolving to survive in a hotter world. In the past few years Scottish sheep have become smaller, while species of birds and plants are moving to cooler climes up mountains and away from the tropics. Carl Zimmer, writing for Yale's green blog Environment 360, details how evolution can move far more swiftly than Darwin had foreseen.
In Canada, for example, red squirrels are coming out of hibernation earlier in the spring; not only are the animals reacting to climate change, but natural selection is favoring squirrels whose genes promote early rises. Yet while evolution may help a few species cope with the hazards of climate change, Zimmer cautions that it's not "an ecological Get-Out-Of-Jail-Free card"; many organisms, particularly longer-lived ones, will be unable to adapt.