As Climate Warms, Bark Beetles March On High-Elevation Forests

Dec. 31, 2012 — Trees and the insects that eat them wage constant war. Insects burrow and munch; trees deploy lethal and disruptive defenses in the form of chemicals.

But in a warming world, where temperatures and seasonal change are in flux, the tide of battle may be shifting in some insects' favor, according to a new study.

In a report published today (Dec. 31, 2012) in the Proceedings of the National Academy of Sciences, a team of scientists from the University of Wisconsin-Madison reports a rising threat to the whitebark pine forests of the northern Rocky Mountains as native mountain pine beetles climb ever higher, attacking trees that have not evolved strong defenses to stop them.

The whitebark pine forests of the western United States and Canada are the forest ecosystems that occur at the highest elevation that sustains trees. It is critical habitat for iconic species such as the grizzly bear and plays an important role in governing the hydrology of the mountain west by shading snow and regulating the flow of meltwater.

"Warming temperatures have allowed tree-killing beetles to thrive in areas that were historically too cold for them most years," explains Ken Raffa, a UW-Madison professor of entomology and a senior author of the new report. "The tree species at these high elevations never evolved strong defenses."

Continued:  http://www.sciencedaily.com/releases/2012/12/121231161015.htm