Science Daily - Beetle Outbreaks Have Already Killed Billions Of Conifers Across N. America

[hatrack]

ScienceDaily (Sep. 21, 2010) — The potential for outbreaks of spruce and mountain pine beetles in western North America's forests is likely to increase significantly in the coming decades, according to a study conducted by USDA Forest Service researchers and their colleagues. Their findings, published in the September issue of the journal BioScience, represent the first comprehensive synthesis of the effects of climate change on bark beetles.

"Native bark beetles are responsible for the death of billions of coniferous trees across millions of acres of forests ranging from Mexico to Alaska," said Barbara Bentz, research entomologist with the Forest Service's Rocky Mountain Research Station and lead author of the study. "Our study begins to explain how their populations respond to the climatic changes being projected by the Intergovernmental Panel on Climate Change." In the study, Bentz and her colleagues synthesized what is currently known about the effects of climate change on several species of bark beetles that cause extensive, landscape-scale tree mortality in North America. They then used a combination of models to analyze the likely response of and generate case studies for two specific species -- the spruce beetle and mountain pine beetle.

"Our models suggest that climatic changes on the order of what is expected would increase the population success of both spruce beetle and mountain pine beetle throughout much of their range, although there is considerable variability," said Chris Fettig, a research entomologist with the Pacific Southwest Research Station and a coauthor of the study. "Bark beetles are influenced directly by shifts in temperature, which affect developmental timing and temperature-induced mortality, and indirectly, through climatic effects on the species associated with beetles and their host trees."

One effect the study detected is the likelihood, in a warming climate, of a substantial increase in areas of spruce forest dominated by spruce beetles that reproduce annually rather than every two years, as is common today. Annual reproduction of the beetle can contribute significantly to population growth and the occurrence of outbreaks.

EDIT

http://www.sciencedaily.com/releases/2010/09/100908171158.htm

[mike_c]

1. this highlights the importance of restoring natural fire ecology to western forests...

...for thinning and maintaining old growth stand characteristics, which are considerably less amenable to beetle population outbreaks than the present overstocked, stressed forests.