Fossil record suggests insect assaults on foliage may increase with warming globe

With implications for present climate, new data links past spike in temperature with increased voraciousness of plant-eating insects

Ellen Currano collecting fossil leaves from a site that is 57 million years old in the Bighorn Basin, Wyoming. Click here for more information.

More than 55 million years ago, the Earth experienced a rapid jump in global carbon dioxide levels that raised temperatures across the planet. Now, researchers studying plants from that time have found that the rising temperatures may have boosted the foraging of insects. As modern temperatures continue to rise, the researchers believe the planet could see increasing crop damage and forest devastation.

The researchers, from Penn State, the Smithsonian Institution, the University of Maryland, the University of California, Santa Barbara, and Wesleyan University published their findings in the Feb. 11, 2008, Proceedings of the National Academy of Sciences.

"Our study convincingly shows that there is a link between temperature and insect feeding on leaves," said lead author Ellen Currano of Pennsylvania State University and the Smithsonian Institution. "When temperature increases, the diversity of insect feeding damage on plant species also increases."

With support from the National Science Foundation (NSF), Currano collected the study fossils from the badlands of Wyoming, gathering more than 5,000 fossil leaves from five sites representing time zones before, during and after the roughly 100,000 year temperature spike called the Paleocene-Eocene Thermal Maximum (PETM).