Pine beetle infestations reduce wildfire severity, study suggests

"In general forests that had insect damage had a lower level of burn severity," said Garrett Meigs, the lead author in the study led by the University of Vermont which examined more than 80 fires over the last 25 years in the Pacific Northwest region of the U.S.

Study examined more than 80 fires over the last 25 years in the Pacific Northwest region of the U.S.

Foresters expect limitations on future timber supplies after provincial forests were devastated by the mountain pine beetle (CBC)

It's been feared that the many millions of dead trees left in the wake of pine beetles infestations would lead to more severe wildfires, but new research suggests that is not the case.

A study that examined more than 80 fires over the last 25 years in the Pacific Northwest region of the U.S. concluded that pine beetle and western spruce budworm infestations did not increase the severity of wildfires, but actually decreased the intensity.

"In general forests that had insect damage had a lower level of burn severity," said Garrett Meigs, the lead author in the study led by the University of Vermont.

"The conventional wisdom is that insect outbreaks increase fire activity, either the likelihood or the severity … so when our results showed this pretty consistent pattern of lower severity in places with insect outbreaks — across a wide range of conditions — it was pretty surprising."

Two destructive insects studied

Meigs said research found that the mountain pine beetle and western spruce budworm affected the forests differently, and the way the fires behaved was also different depending on the time since the infestations occurred.

"In fact the two insects had sort of the opposite pattern, where over time [for] the mountain pine beetle, the effect on burn severity got lower and lower, and the spruce budworm actually initially had very low severity fire, but then it increased over time," he said.

Meigs said the results are applicable to B.C., where 18.1 million hectares of forest have been infected by the pine beetle, according to the B.C. government.

However he said it is only "one piece of a pretty complicated puzzle."

How findings could be used

"Other aspects of insect-fire interactions include the connection between insects and fire likelihood and fire spread. This study just focused on the severity."

He said the findings could be used by forest managers.

"When it comes to being able to make decisions about where to have forest management activities, to do firefighting, to allocate those kinds of resources, they could take this study into account which suggests that some of the insect outbreak areas at least in Oregon and Washington are less of a fire hazard than we expected."

With files from CBC's Radio West


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