Bark beetle scourge felt outside Colorado
January 22, 2007
BILLINGS, Mont. (AP) – This story will ring a bell for Eagle County residents: Beetles smaller than a grain of rice continue to choke off and kill thousands of whitebark pine trees and other species in and around Yellowstone National Park.Just like in the forests of the Rockies, mountain pine beetles have been hungrily burrowing into Yellowstone’s trees for years as part of a large-scale outbreak that some experts say is part of a natural cycle and others tie to global climate change.Some had hoped that a few cold snaps last winter would have killed off many of the beetles. But when last summer rolled around, the bugs were back at it.Roy Renkin, a vegetation expert at Yellowstone National Park, said he was taken aback last year during a trip to a part of the park called Avalanche Peak. Vast stands of whitebark pines – trees that grow in high elevations and produce a fatty nut that is an important food for grizzly bears – have been hit hard by the beetles. “It was just a red carpet,” Renkin said, referring to the color needles turn as they die. “It didn’t look like there was a living tree down there.”
Last week the U.S. Forest Service released a report of bark beetle conditions in the Northern Rockies culled from aerial and ground surveys.The 2006 report is a mixed bag. In many places, fewer affected trees appeared in Western Montana and northern Idaho. That’s probably the function of more moisture, which makes trees stronger and better able to fight off the beetles. Last year, the mountain pine beetle swept through about 881,000 acres of forest in the region, down from more than 1 million acres estimated in 2005. On those infested acres, about 2.4 million trees were killed, more than 80 percent of which were lodgepole pine, the report said.While weather may have dampened some bark beetle activity, the mountain pine beetle seems to be going strong, and with no relief in sight.”They just go through until they don’t have anything left to kill,” said Ken Gibson, an entomologist with the Forest Service in Missoula.The beetles occur naturally and act as a forest regulator, spurring on life-and-death cycles that kill trees – usually by digging beneath the bark in large numbers and stifling the flow of nutrients – and recycle nutrients in the forest.Mountain pine beetles and other bark beetles go through periodic outbreaks, including those in the Yellowstone area in the 1930s and 1970s.In recent years, large outbreaks have been recorded from Arizona to Montana – including the Colorado Rocky Mountains – and in parts of Canada and Alaska.One of the top concerns in the Yellowstone area is with whitebark pine trees, a key species at high elevations.
Jesse Logan, a retired U.S. Forest Service entomologist who studied bark beetles for 30 years, said his visits to Yellowstone showed many places where whitebark pine infestation seems to be worsening.The death of whitebark trees has a ripple effect. The trees play an important role in holding and controlling snow as it melts from high elevation. It also produces a high-protein nut that’s important in the diet of grizzlies and other animals.
“I see what’s going on in whitebark is really a true ecological threat,” Logan said.Logan said it’s clear to him that the outbreak is linked to climate and man’s role in making it warmer. Above-normal temperatures allow beetles to survive winters, breed faster and move to higher elevations in places where they have rarely been.”I think the evidence is so overwhelming,” Logan said of climate change.He is pushing for an assessment of the greater Yellowstone ecosystem to look specifically at the effect of mountain pine beetles on whitebark pine.”This is an issue that is very immediate,” Logan said.Gibson is wondering whether the January cold snap, which included temperatures down to 40 below zero to minus 50 in higher elevations, will mean fewer beetles this summer. Even better, he said, would be a prolonged cold snap in the fall, when the beetles are more vulnerable.It’s hard to say when the outbreak will die down significantly.”I expect 2007 is going to be another busy year for insects,” Gibson said.