Ancient Global Warming Gave Bugs the Munchies

February 11, 2008

A temperature spike about 55 million years ago gave bugs the munchies, according to a new study.

If modern temperatures continue to rise as anticipated in the coming years, researchers add, the planet could see a similar increase in insect damage to crops and other plants.

The finding is based on an analysis of more than 5,000 fossil leaves that were ravaged by voracious insects dating to before, during, and after the ancient bout of global warming.

"We see a huge increase in the percent of plants that are being attacked," said Ellen Currano, a graduate student in geosciences at Pennsylvania State University in University Park.

The research appears this week in the journal Proceedings of the National Academy of Sciences.

Michael Storey is a geochronologist at Roskilde University in Denmark and an expert on the ancient temperature spike, called the Paleocene-Eocene Thermal Maximum (PETM) because it straddles the two geologic eras. (See a geologic time line.)

Storey said that the PETM is "the best natural analog" to modern warming and that studies like Currano's "reveal more and more about what potentially will happen when we change the climate."

Less Filling

Currano and colleagues collected the fossil leaves from the badlands of Wyoming.

Some leaves have giant holes chewed through them; other fossils are just the leaf skeleton—the veins—because all the other tissue was eaten.

Some of the leaves had galls, which are tumor-like growths that form around insect eggs laid inside the leaves. Another type of damage, called leaf mines, occurs when eggs laid in the leaf hatch and the larvae chew passages on their way out.

"You can see that trail where there's no leaf tissue inside anymore, and in some cases you can see the fossil poop that the insect has left behind," Currano said.

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