The severity of insect outbreaks and wildfires has increased in recent years that some scientists and policy makers have drawn a correlation between the two.
Findings of a new study, however, revealed that there is a negative link between the two such that the outbreaks of insects, such as the western spruce budworm and mountain pine beetle, were found to help reduce the severity of wildfires.
For the research, which was published in the journal Environmental Research Letters on April 21, University of Vermont forest scientist Garrett Meigs and colleagues analysed 81 fires that occurred over a span of 25 years, focusing on sites with past insect outbreaks.
Using satellite imagery to evaluate vegetation loss, the researchers found that wildfires in areas that had greater insect damage were marked by less severe burning regardless of the season, fire size and drought conditions.
The researchers said this can be attributed to "forest thinning." This happens when insects kill some of the trees and leave others to thrive, lowering forest density, which cuts the amount of fuel that may worsen subsequent fires.
The insects likely kill the weakest trees while leaving others to survive, which leaves the forest with less flammable mass.
Meigs said the findings suggest that insects do not just reduce the odds of fire. They can also reduce their potential impacts.
"Native insects contribute to landscape-scale heterogeneity, potentially enhancing forest resistance and resilience to wildfire," the researchers wrote in their study. "Because insect outbreaks do not necessarily increase the severity of subsequent wildfires, we suggest a precautionary approach when designing and implementing forest management policies aimed at reducing wildfire hazard in insect-altered forests."
Study researcher Bill Keeton, also from the UVM, said climate change prompts concerns that incidences of insect outbreak and forest fire will continue to grow. The study, however, may provide valuable information on forest management.
"These threats remain significant, but our study suggests that major insect outbreaks, contrary to current thinking, can dampen future fire impacts – and we can use that knowledge to improve forest management," Keeton said. "These findings will help forest managers to better prioritize restoration efforts designed to reduce fire risks."
The Forest Service looks into the issue and currently uses fire-prediction models that would analyse how forests with insect outbreaks may react to fire.