It’s been more than a decade since a bark beetle epidemic wiped out swaths of piñon trees around Santa Fe, but a growing body of research predicts that warming winters could spell trouble for beetle-prone conifers in the area — and beyond.
A new study by Los Alamos National Laboratory is the first large-scale analysis to demonstrate that higher temperatures allow the destructive beetle to multiply rapidly and expand its range.
The study also found that the pest’s population growth is limited by competition for food. In other words, there’s only so much sustenance in each tree.
“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,” said Devin Goodsman, a postdoctoral researcher at the lab and the study’s lead author. “That can have a countering effect.”
Still, Goodsman said, colder winters would be the best defense against an epidemic.
The study used samples from 10,000 trees, collected over nine years and across 22 million acres in the Canadian province of Alberta.
Researchers from Utah State University, the University of Minnesota, the Canadian Forest Service, Pacific Northwest National Laboratory and the Alberta Forestry Division co-authored the study, which was sponsored in part by LANL and published in the journal Global Change Biology.
Goodsman hopes the study’s findings will allow researchers to build a computer model to predict tree mortality during epidemics, while also aiding forestry officials in improving management practices.
He said climate change could be dealing the region’s conifers a double blow: Not only do warming winters help beetles survive, but drier seasons make trees more susceptible to a beetle invasion. Bark beetles can sense a fragile tree and alert their brethren to join the feast.
The study comes on the heels of one of the driest winters on record in New Mexico, with extreme and exceptional drought covering 60 percent of the state, according to the U.S. Drought Monitor.
Still, entomologists and tree experts said they don’t expect this year to bring an outsized incidence of tree destruction because of bark beetles.
If anything, this will be a building year.
“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.”
So far this year, beetles have targeted ponderosa pine and Douglas fir trees in the Santa Fe National Forest, Coleman said.
Robert Coates of Coates Tree Service said he’s seen “very minor issues” with bark beetles.
“We’re sort of expecting we’re going to get some action later this year,” he said. “But then, if we have a really good monsoon, that could abate it somewhat.”
Coates said monthly slow, deep watering of conifers is the best defense against bark beetles. Still, it’s not a fix-all solution.
“There will be trees here and there getting attacked, but that happens on any year because it’s a natural phenomenon,” he said.
The term bark beetle is a broad classification that refers to more than 6,000 species of beetles that reproduce in the inner bark of trees. From 2001-05, the piñon ips, a tree-killing species, laid its eggs in drought-weakened piñon trees in and around Santa Fe, decimating populations along N.M. 599 and near Interstate 25 between the city and Eldorado.
The matchstick head-sized insects are also prone to fell spruce trees and other conifers. They don’t destroy the trees themselves, instead transmitting a deadly fungus.
Once the tree is infected, Coates said, the best thing to do is remove it — and quickly.