BILLINGS — A pine beetle outbreak that has left many Western states with vast stands of dead and dying trees has eased for the second consecutive year, the U.S. Forest Service said Monday.
With fewer trees left for the beetles to eat, officials said a 2011 aerial survey recorded beetle-killed trees on 3.8 million acres of public and private land. That’s down by more than half from 2009, when about 9 million acres with dead trees were tallied.
But the good news is tempered by more trees dying at higher elevations as beetles take advantage of warm winters to gain a new foothold, said Robert Mangold, the Forest Service’s acting associate deputy chief for research and development. And with trees on roughly 42 million acres killed by various beetles since 2000, it could take decades for some forests to fully recover.
Beetle outbreaks can lead to more intense wildfires and hurt timber companies by making some trees unsuitable to harvest.
Montana recorded the most beetle kill acreage in 2011, with dead trees across almost one million acres. Idaho, Colorado, Wyoming and Oregon also had significant losses.
Mountain pine beetle are native to the region and their outbreaks are cyclical, but the current one has been the worst in at least three decades. Mangold said it was too soon to say if the decreasing mortality seen over the last two years is a trend that will continue.
“You run into trouble saying the worst is over,” Mangold said. “People are still suffering.”
The beetle’s 2011 retreat helped drive a nationwide decline in trees killed by insects and disease. Dead trees seen on 6.4 million acres of public and private land in 2011, compared to 9.2 million acres in 2010.
Pine beetles accounted for about 60 percent of all tree mortality last year.
Most of the forests they damaged are expected to recover, although Mangold added that if a dead stand is overrun by a wildfire and burns hot enough, the soil can be depleted and it can be harder for trees to begin regenerating.
For those forests to reach maturity will take much longer, possibly as much as a century or more, said Frank Maus, manager of the University of Montana’s Lubrecht Experimental Forest east of Missoula.
In the interim, Maus said, the effects of the outbreak will continue to be felt for years to come.
Timber companies that wait too long to harvest beetle-damaged stands risk having the trees crack due to dry weather. Also, the amount of fuel on the forest floor that could help stoke future wildfires will continue to grow as dead trees rot and topple.
“Mother Nature’s time frame is hard for us to get used to,” Maus said. “She’s talking hundreds of years and we’d like to see it in our lifetime.”