Earthwatch teams research impact of Hurricane Katrina

Earthwatch Institute, Maynard, MA, November 17, 2005-Climate change may spell disaster for agricultural crops and forests, in the form of caterpillar outbreaks, according to a paper published this week online in the Proceedings of the National Academy of Sciences. The paper links increasing climatic unpredictability, including extreme storms such as Hurricane Katrina, to decreasing levels of parasitism by wasps and flies that control caterpillar populations.

"This finding is potentially very significant," said Dr. Lee Dyer, an ecologist at Tulane University and principal investigator of Earthwatch Institute's Forest Caterpillars project. Dyer, who is a co-author of the paper, explains, "It could mean that the parasite services that we take for granted may start declining as climate change drives more of these extreme weather events. Because parasites are a key regulator of insect herbivores, we speculate that damaging outbreaks in natural and agricultural systems will become more common."

Most animals rely on environmental cues, and scientists predict that climate change may adversely affect their behaviors. Such effects are likely to be more pronounced in predators, as these animals have to cope with both changes in climate and subsequent changes in the behavior of their prey. The same could be said of the parasitic wasps and flies that play an important role in controlling insect pest populations.

The authors used caterpillar parasitism data from 15 insect-rearing programs ranging from Canada to Brazil, comparing these data to year-to-year rainfall variations for each region. They found that the overall frequency of parasitism against caterpillars decreased as climatic variability increased. No other environmental factors measured accounted for this pattern, suggesting that unpredictable rainfall patterns are disrupting the ability of parasitic wasps and flies to track their prey.

The PNAS paper included data from Dyer's caterpillar-rearing programs at La Selva, Costa Rica and Yanayacu, Ecuador, supported by the efforts of Earthwatch teams. It also included data from Arizona and Louisiana, where Dyer has recently expanded his Earthwatch teams to explore caterpillar parasites still further.

"We could not have collected data at La Selva and Ecuador without Earthwatch volunteers," said Dyer. "For most years over the last decade, our Earthwatch funding was the only financial support we had for this project, in addition to National Geographic funding for the Costa Rica site."

Earthwatch teams are now being recruited to work in New Orleans, the site of Dyer's lab at Tulane, to help examine parasitism on caterpillar populations affected by Hurricane Katrina, with findings very relevant to the present paper. Teams will also be working to restore Tulane labs damaged by the storm, a valuable opportunity to both help the restoration effort and learn more about the ecological aftermath.

"They will be working with our insect collection, which provides more specific data for looking closely at these interesting relationships," added Dyer.

Earthwatch Institute is an international nonprofit organization that supports scientific field research by offering members of the public opportunities to work alongside leading field scientists and researchers. Earthwatch's mission is to engage people worldwide in scientific field research and education and promote the understanding and action necessary for a sustainable environment.

For more information, see "Climatic unpredictability and parasitism of caterpillars: implications of global warming." J.O. Stireman III, L.A. Dyer, D.H. Janzen, M.S. Singer, J.T. Lill, R.J. Marquis, R.E. Ricklefs, G.L. Gentry, W. Hallwachs, P.D. Coley, J.A. Barone, H.F. Greeney, H. Connahs, P. Barbosa, H.C. Morais, and I.R. Diniz. PNAS, 102 (48): 17384-17383.

For Lee Dyer's personal commentary, photos, and links about the impact of Hurricane Katrina, go to http://www.tulane.edu/~ldyer/neworleans1105.htm