Study: Warming winters could lead to bark beetle spread

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Bark beetles damaged this ponderosa pine in southern New Mexico's Lincoln National Forest. Aerial and ground surveys done by state and federal forestry officials show an increase in tree mortality in the Sacramento Mountains due to drought and beetle infestations. (Source: The U.S. Forest Service)

SANTA FE – A bark beetle epidemic wiped out swaths of piñon trees around Santa Fe more than a decade ago, and now new research predicts that warming winters could spell more trouble.

Scientists at Los Alamos National Laboratory have done a large-scale analysis to demonstrate that higher temperatures allow the destructive beetle to multiply rapidly and expand its range, the Santa Fe New Mexican reported last week.

Bark beetle is a broad classification that includes more than 6,000 beetle species that reproduce in the inner bark of trees. Populations of piñon trees around Santa Fe were decimated from 2001 to 2005 after beetles infested the drought-weakened trees.

While more beetles may stick around in warmer winters, the population growth is limited by competition for food, said researcher Devin Goodsman, the lead author of the study.

“If these beetles are living better because they’re not dying due to cold, there are more of them around to compete with one another,” Goodsman said. “That can have a countering effect.”

The study could allow researchers to build a computer model to predict tree mortality during epidemics, which could also support forestry officials in improving management practices, Goodsman said.

Drier seasons make trees more susceptible to beetle infestations, so the changing climate may deal a double blow to the region’s conifers, Goodsman said. Bark beetles can sense a fragile tree and alert fellow pests.

New Mexico had one of its driest winters on record with extreme and exceptional drought conditions covering about 60 percent of the state, according to the U.S. Drought Monitor.

“Usually two years of drought stress are what’s needed to see the elevated tree mortality,” said Tom Coleman, an entomologist with the U.S. Forest Service. “We’re beginning to see populations build this year. If we get a good wet winter next year, it’ll basically knock them out.”

Beetles have been found in ponderosa pine and Douglas fir trees in the Santa Fe National Forest this year, Coleman said.

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