Climate Change to Bring Plagues of Insects?

A fossil leaf from the Paleocene-Eocene Thermal Maximum shows extensive insect damage. (Photo by Amy Morey.)New research from the National Science Foundation suggests a warming Earth could mean a significant increase in voracious, plant-eating insects.

Scientists studying the Paleocene-Eocene Thermal Maximum (PETM), a period about 55 million years ago when global carbon dioxide levels spiked rapidly, found that plant fossils from that time show noticeably more insect damage than plants from before or after the PETM. They found no evidence that the plants themselves had become more appetizing to insects, or that insect species themselves changed. Rather, it appears that the PETM simply was a time when insects became more voracious and destructive.

Part of the reason might be that plants grown in high-carbon dioxide conditions are less nutritious than they otherwise would be. Some scientists have speculated that might have been the reason dinosaurs grew so large: to be able to take in large enough volumes of plant material to sustain them.

The high-temperature PETM lasted about 100,000 years.

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

Today’s tropics already illustrate that phenomenon, as insects there eat more plants than do their temperate-zone counterparts. Insects are also among the warm-weather species now expanding their ranges as average temperatures around the globe rise.

The researchers’ findings suggest that insects could wreak greater damage to crops and forests around the planet as the climate continues to change.

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