Why Leaves Turn Red

Scientists have long wondered if the red color of fall leaves was more than just a sign of death. The process of turning leaves to brilliant colors requires energy, but doesn't seem to benefit the trees.

Some have suggested that fall colors act as sunscreen and keep trees from freezing. In 2001, British evolutionary biologist William Hamilton suggested the color might ward off bugs that would otherwise feast on the tree.

Hamilton looks to be on to something, a new study suggests. And the methodology is cool: Researchers found red fall leaves are prevalent among wild apple trees in China. But cultivated versions of those trees in Britain today aren't near as likely to turn red because "farmers crossbred the trees with the largest, tastiest fruit, rather than selecting the ones most resistant to insect pests," the thinking goes.

Seems the red, as elsewhere in nature, acts as a useful red flag.