Global warming brings out the bugs -- study
Agence France-Presse
First Posted 08:33:00 02/12/2008
CHICAGO -- New research into an earlier chapter of global warming in Earth's history suggests the current period of climate change will accelerate crop damage and forest devastation, a study released Monday said.
Researchers who studied the impact of this earlier warming period on prehistoric foliage found it coincided with increased damage to the plants due to greater insect feeding.
Prehistoric plant life appeared to have been subjected to an intense assault by an unusually abundant and voracious insect population.
Investigators believe rising temperatures allowed insects from the tropics to migrate to new habitats in traditionally cooler latitudes, while higher carbon dioxide levels made it harder for them to get the nutrition they needed from the plants.
"Our study convincingly shows that there is a link between temperature and insect feeding on leaves," said Ellen Currano, a graduate student at Pennsylvania State University.
"When temperature increases, the diversity of insect feeding damage on plant species also increases," added the lead author of the paper in the Proceedings of the National Academy of Sciences (PNAS).
Currano and colleagues examined more than 5,000 leaf fossils they recovered from the Bighorn Basin in Wyoming in the western United States, dating from a period called the Paleocene-Eocene Thermal Maximum (PETM), and the years immediately before and after that.
The PETM is the name given to an abrupt warming period that occurred about 56 million years ago and coincided with a temporary tripling of carbon dioxide in the atmosphere. Temperatures spiked by four, and in some places as much as 10, degrees Celsius.
Scientists say this earlier period of climate change is comparable to the contemporary global warming phenomenon which is driven in large part by greenhouse gas emissions.
When Currano and her colleagues studied the fossilized leaves from the PETM, they found they had much heavier insect feeding damage than the leaves from the years either side of that geologic period.
The evidence suggested that a greater diversity and number of predators were feeding on the plants -- and feeding harder -- than before or after.
Previous research has shown that animals extend their ranges as temperatures rise. It has also shown that plants grown under higher concentrations of carbon dioxide are less nutritious, so insects must eat more.
"If what happened then is representative of what might happen today, we would expect to see insects from the tropics and sub-tropics move to northerly and southerly latitudes, and more feeding damage on plants that grow in those regions," Currano said.
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