New research by the U.S. Forest Service takes an in-depth look at the effect of climate change on tree-killing bark beetles.
Their conclusion? The warmer climate predicted by the International Panel on Climate Change will likely yield more bark beetle outbreaks, which will kill more trees.
Bark beetles have already destroyed billions of coniferous trees from Alaska to Mexico, in part because winter temperatures aren’t getting cold enough to kill brood stocks.
The potential for outbreaks of spruce and mountain pine beetles, in particular, is likely to increase significantly in the coming decades, the study found. The beetles are native to the West, but warmer temperatures, drier climates and overstocked forests help spread the beetles and trigger outbreaks that kill large swaths of trees.
The new research findings, published in the September issue of the journal BioScience, provide the first comprehensive analysis of the effects of climate change on bark beetles. They also highlight some of the changes foresters expect to see in the coming decades – like an expansion of the Ponderosa pine forest range.
I got a chance to interview entomologist Chris Fettig of the Pacific Southwest Research Station about the findings, and will post the Q&A soon.
He and Barbara Bentz, research entomologist with the Forest Service’s Rocky Mountain Research Station and lead author of the study, combined several models of what is currently known about the effects of climate change on bark beetles that cause landscape-scale tree mortality to reach their conclusions. One scenario for the spruce beetle shows the insect reproducing once a year in a warmer climate instead of once every two years as it commonly does now - a pretty significant change.
“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 Fettig. “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.”
However, the research found low to moderate risk of the mountain pine beetles expanding their range across forests of central Canada and into the central and eastern United States. That had been a major concern up until now.