Colorado temps not low enough to kill pine beetles
The Aspen Times
Aspen, CO Colorado
EAGLE COUNTY, Colo. – The frigid air that Colorado endured in recent days wasn’t quite nasty enough to harm the mountain pine beetle population that has killed millions of lodgepole pine trees.
The mountain pine beetle, which has been affecting forests after an extended drought in the late 1990s and early 2000s, has infested more than 1.5 million acres of forest in northern Colorado and southern Wyoming. The epidemic spreads into Canada, and local Forest Service officials say it’s the worst beetle epidemic in history.
Sky Stephens, a Colorado Forest Service forest entomologist, said the arctic blast that came over the state last week probably didn’t slow the epidemic.
“We need about 72 straight hours of 30 below (zero), not just an overnight low,” Stephens said. “We’ve had some drastically cold temperatures, but I don’t know of any area that’s had the sustained cold temperatures to sustain (beetle) mortality.”
The timing of extreme low temperatures also plays a part in whether the mountain pine beetle population is affected. In the late fall and early winter, the beetles are turning sugar into glycol, which acts as a natural antifreeze. By January and February, the beetles already have built up so much glycol that they’re resistant to the lower temperatures.
And even if the cold air descended on the state at the perfect time, Stephens said the epidemic is so widespread and the population is so huge that it likely wouldn’t make much of a difference.
“With the acreage in Colorado now infected, it just wouldn’t be that impactful,” Stephens said.
Cal Wettstein, the beetle kill incident commander for the U.S. Forest Service, said if extreme cold happens early on, when the beetles haven’t adapted yet, it’s more likely to kill them.
But Wettstein said the beetles have already done so much damage that even a bitter cold snap for an extended period of time probably wouldn’t matter much in terms of forest health.
“They’re on track now to eat themselves out of house and home,” Wettstein said. “As far as the Western Slope, it’s done most of its damage. It will continue to kill most of the green trees there, too.”
Wettstein said that about 50 million acres across the West have been affected by the mountain pine beetle epidemic. The latest aerial survey of the Western Slope shows the beetles have gotten into just about all the pine they can, he said.
The damage has been so widespread because the beetles had what Stephens calls a perfect storm of susceptible trees. An overcrowded forest entered the same stage of tree age and health at the same time, and combined with a long drought, “we had lots of stressed-out trees that were essentially ripe for the picking,” she said.
The most immediate concerns from the epidemic are falling trees, Wettstein said. Trees are falling at increasing rates throughout the forests, he said.
When all those trees fall down, it will create a heavy fuel bed, which probably will enter its worst stage in about 20 to 30 years, he said.
“That’s why we’re cleaning up now around communities,” Wettstein said. “In the big scheme of things, it’s all part of a natural cycle. It just makes it difficult when (people have) moved right into it.”
Stephens said it’s essential to prepare for the future now that the epidemic has done most of its work.
“When we start managing these future forests, we have to recognize the types of management decisions we have to make,” Stephens said.
Options include planting seeds to diversify the forest, allowing wildfires to burn in areas that don’t threaten infrastructure, and timber harvesting or logging. Stephens said logging doesn’t have to mean clear-cuts, either, but merely enough to thin out sections of the forest to make room for young tree stands to emerge.
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