Rising temperatures spur biological chaos.

• Position: Climate

Global warming is having a significant impact on hundreds of plant and animal species around the world, although the most-dramatic effects may not be felt for decades, according to a Stanford (Calif.) University study. "Birds are laying eggs earlier than usual; plants are flowering earlier; and mammals are breaking hibernation sooner," Terry L. Root, a senior fellow with Stanford University's Institute for International Studies and lead author of the research, points out.

"Clearly, if such ecological changes are now being detected when the globe has warmed by an estimated average of only 1[degrees]F over the past 100 years, then many more far-reaching effects on species and ecosystems will probably occur by 2100, when temperatures could increase as much as 11[degrees]F."

Root and her colleagues analyzed 143 scientific studies involving a total of 1,473 species of animals and plants. Each found a direct correlation between global warming and biological change somewhere in the world. For instance, research revealed that, as temperatures increased in recent decades, certain species began breeding and migrating earlier than expected. Other studies found that the geographical range of numerous species had shifted poleward or moved to a higher elevation--indicating that some plants and animals are occupying areas that were previously too cold for survival.

Root and her coworkers contend that nearly 1,200 species--roughly 81% of the total number analyzed--have undergone biological changes that were "consistent with our understanding of how temperature change influences various traits of a variety of species and populations from around the globe." Their research involving temperate-zone species revealed that springtime events--such as blooming, egg laying, and the end of hibernation--now occur about 5.1 days earlier per decade on average.

North American tree swallows offer a good example. Field biologists, who kept track of some 21,000 of those birds' nests in the U.S. and Canada over the last 40 years, concluded that the average egg-laying date for female swallows has advanced by nine days--a phenomenon that mirrors other North American studies confirming higher temperatures and the earlier...