Beetles alone may not raise fire threat
SUMMIT COUNTY ” The link between fire risk and the pine beetle epidemic sweeping through Colorado forests may not be as conclusive as generally assumed, according to Forest Service research.
Based on a recent review of relevant studies, Forest Service scientists said there is no huge amount of evidence suggesting that insect outbreaks significantly increase the fire risk in a given area.
However, large areas of recently dead trees still carrying red needles can result in a more intense fire and enable such a blaze to spread more rapidly.
The biggest risk to long-term forest health may come from super-hot, earth-baking fires 20 to 30 years after a bug infestation, when the trees are dead on the ground. And even then, it’s important to remember that lodgepole forest ecology is marked by episodes of destruction and renewal.
That doesn’t mean work should stop on trying to limit the threat of fires near homes, town and important infrastructure.
“The life cycles of these (lodgepole) forests are punctuated by extreme events,” said Dr. Mark Finney, a Montana-based Forest Service fire researcher. “Running out there willy-nilly to try and solve this problem probably won’t help.
“All this talk, all this worry that we have an emergency might just go away in a year of two on its own,” Finney said.
Once the needles have dropped off the beetle-killed trees, they are less susceptible to a rapidly spreading crown fire than green-topped trees, he said.
By the time a treatment is planned, reviewed and implemented, the most extreme period of immediate fire danger may already be long gone. Thus, human efforts to address beetle kill and fire danger are far behind the curve, he added.
“The time to improve a stand’s health is before the bugs get in,” he said. “Destroying a whole stand is not a bad thing, ecologically.”
Finney cited recent fires in the Black Hills of South Dakota as an example where it was assumed a beetle epidemic had contributed to the fires.
“It’s tempting to draw conclusions,” he said.
But a close comparison of fire history maps and the pattern of pine beetle infestations in that area failed to show a close geographic overlap, he explained.
Finney did acknowledge that Summit County could be facing somewhat of a worst-case scenario, with “mile upon mile of trees dying within a short time.” In that situation, the potential for a rapidly spreading “mega-fire” could indeed be high, at least for the one to two years when the trees are still carrying the dead, red needles high in their branches.
At least some of the information reaching the public concerning the fire danger associated with beetle-killed trees has been muddled by generalizations and misconceptions, said Dr. Wayne Shepperd, a forest ecologist with the Forest Service’s Rocky Mountain Research Station.
As recently as last week’s Summit County pine beetle task force meeting, local residents heard about the impending fire risk.
“It’s still looking pretty green right now ” in a couple of years, it won’t be so green and the fire danger will increase astronomically … most of our trees will be red,” said Sandy Briggs, of Our Future Summit, the grassroots umbrella group for the task force. “The fire danger will be extreme at that time.”
Shepperd said Briggs is partially correct to assume that lodgepoles with red needles are more flammable. But at best, that may be an over-simplification.
The reality is much more nuanced, with the fire risk depending on other significant factors, including dead vegetation on the forest floor, wind and weather, he explained. A drought-stricken lodgepole pine forest with green trees on a hot and windy day can be just as susceptible to a big fire as a beetle-killed stand.
Focusing on beetle-kill at the expense of other factors could result in a faulty rationale for decision-making, both scientists said.
“There’s a popular misconception that the bugs turn the trees red and that equals more fires,” Shepperd said. “Red trees do not appreciably increase the fire risk. At least many of our scientists say no.”
There is no increased risk of fire ignition based simply on the fact that the trees are dead, Shepperd said.
The message coming out of the agency’s fire lab in Montana is that the science on how insect-damaged forests affect fire behavior is still limited, but the research so far shows that those effects depend on the types of insects, the percentage of trees affected, elapsed time since the infestation and what kind of vegetation is around to fuel a fire.
For an overview of the latest Forest Service efforts to manage insect infestations, go to http://www.fs.fed.us/foresthealth/publications/wbbi_assessment.pdf.
Vail Daily, Vail, Colorado
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