Pine Beetle Infestations Won’t Spark More Flames: Study

Western pine forests that have been devastated by pine beetles at least have one respite according to new research: They are not more likely to burn.

“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,” said Sarah Hart, a postdoctoral researcher at the University of Colorado-Boulder and lead author of a study in Proceedings of the National Academy of Sciences.

“The bottom line is that forests infested by the mountain pine beetle are not more likely to burn at a regional scale.”

Mountain pine beetles (Dendroctonus ponderosae) have laid waste to more than 24,700 square miles of forest in the western U.S., killing trees from Alaska to California. Some researchers have hypothesized that the excess dead trees may be easy kindling for wildfires, and Hart and her team wanted to look at the problem on a large scale rather than the more regional studies that have taken place previously.

They produced maps by looking at multiple years of fire and beetle activity using ground, airplane and satellite data from the U.S. Forest Service and U.S. Geological Survey.

“What we are seeing in this study is that at broad scales, fire does not necessarily follow mountain pine beetles,” said Tania Schoennagel, a research scientist with CU-Boulder’s Institute of Arctic and Alpine Research. “It’s well known, however, that fire does follow drought.”

In fact, Schoennagel and her colleagues found that factors such as increasing temperatures due to climate change and drought that has gripped the U.S. Southwest since 2002 have led to more fires.

This finding has implications for the way government agencies spend money on forest thinning or other fire mitigation strategies, which Schoennagel said may not be an effective use of budgets.

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