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Beetles aren't to blame for forest fires, study confirms

"The bottom line is that forests infested by the mountain pine beetle are not more likely to burn at a regional scale," lead study author Sarah Hart said.

By Brooks Hays
Beetles aren't to blame for forest fires, study confirms
Pine beetle infestations aren't responsible for the growing threat of forest fires in the West, according to new research. File photo by Jim Ruymen/UPI | License Photo

BOULDER, Colo., March 25 (UPI) -- Over the last two decades, the mountain pine beetle (Dendroctonus ponderosae) has infested millions of acres of forest in the Rocky Mountains.

But while the small, black-colored species of bark beetle may be destroying ponderosa and lodgepole pine trees, it's not making forest fires more probable or powerful -- that according to researchers at the University of Colorado Boulder.

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The beetle and microbial partners can be found infesting pine trees throughout western North America, stretching from Mexico to central British Columbia. And the insect's destruction has grown more prevalent in recent years, as warmer temperatures and lengthier droughts both encourage the pest's population growth and weaken trees' defense mechanisms.

With pine beetle outbreaks precipitating severe rises in tree mortality, it was only logical to assume forests full of dying wood would be more susceptible to forest fire. Such logic has dictated local forest and wildfire management policies, and several small scale studies confirmed the logic's scientific bonafides.

But while those studies were confined to only one or two small, localized fires, the new research features more comprehensive regional analysis, overlaying mapped records of beetle infestation and forest fires.

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Researchers looked at forest fire records from the American West in 2006, 2007 and 2012 -- all peak burn years. By comparing the burned areas to records of mountain pine beetle infestations, they were able to determine that fires weren't more likely to torch beetle-hosting forests than concentrations of healthy trees.

"The bottom line is that forests infested by the mountain pine beetle are not more likely to burn at a regional scale," lead study author Sarah Hart, a postdoctoral researcher at Colorado, said in a press release. "We found that alterations in the forest infested by the mountain pine beetle are not as important in fires as overriding drivers like climate and topography."

Rising temperatures and drought are the true drivers of forest fires, researchers concluded -- not mountain pine beetles. The research calls into question the wisdom of thinning forests infected by pine beetles -- a common, yet controversial strategy that allows loggers to strip dead and dying trees as a way to prevent fires.

"These results refute the assumption that increased bark beetle activity has increased area burned," the researchers in wrote in the new study, published this week in the journal PNAS. "Therefore, policy discussions should focus on societal adaptation to the effect of the underlying drivers: warmer temperatures and increased drought."

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