Pine beetle harm wanes as spruce bugs pop up
The growth rate of the spruce beetle infestation on the West Slope spiked last year, even as the numbers of mountain pine beetle appear to be on the decline, according to an aerial survey of Colorado’s forests.
Statewide, the spruce beetle was active on 216,000 new acres in Colorado, according to the 2013 aerial forest health survey conducted by the U.S. and Colorado forest services.
In 2012, the survey found 183,000 new acres of forested lands affected by the beetle, bringing the two-year total to nearly 400,000 acres. Since 1996, the spruce beetle has reached a total of more than 1.1 million acres.
“This increase of activity is indicative of a rapidly expanding outbreak,” the U.S. Forest Service said on its website. “In some areas, the outbreak has moved through entire drainages in the course of one year. In the most heavily impacted drainages, nearly every mature spruce has been killed from the creek bottoms all the way up to the high-elevation krummholz.”
“Krummholz” refers to areas subject to constant exposure to gusting, freezing winds.
The survey underscores what U.S. Forest Service officials have said previously — that there is little they can do to halt the onslaught of the spruce beetle, though they hope to blunt some of its most undesirable effects.
“We’re going to continue to work with local and state officials toward restoration of affected areas where we can, not with a presumption that we can stop it, but to lessen the impacts,” said Lee Ann Loupe, spokeswoman for the Grand Mesa, Uncompahgre and Gunnison national forests, which are administered from Delta.
The Gunnison National Forest seems in particular to be high on the spruce-beetle menu, Loupe said.
It’s munching through La Garita wilderness and into the rest of the forest, Loupe said.
The survey documented 34,000 new acres of infestation, bringing the number of affected areas to 44,000. On the Grand Mesa National Forest, 8,000 new areas of affected trees were discovered, bringing the total to 24,000 acres in which the beetle is active.
The depredations of the spruce beetle play out differently than is the case with the mountain pine beetle, which has laid waste to the lodgepole and ponderosa forests of central Colorado’s mountains.
Trees killed by the mountain pine beetle turn red and orange as they die and dry in the forest. Trees killed by the spruce beetle turn gray, leaving them nearly indistinguishable from healthy trees.
The survey found the mountain pine beetle active on 97,000 acres in 2013, the lowest number of affected acres observed in 15 years, the Forest Service said.
The total number of acres that were affected since the outbreak in 1996 is 3.4 million.
The spruce beetle infestation is a natural condition, Loupe said, but its long-term effects are unknown. Whether spruce forests can regenerate is subject to a variety of localized factors that can’t be easily predicted, she said.