Beetles create “perfect storm” for mass forest death By Leah Todd July 4, 2012 This story is the first in a series examining the effects of the Mountain Pine Beetle epidemic on forests, wildlife and wildfires, and highlighting the U.S. Forest Service’s efforts in managing the situation.
Since Mountain Pine Beetle populations reached epidemic numbers in the mid-1990s,the tiny bug has spotted more than 41 million acres of U.S. forestlands with dead, dry trees. In southeastern Wyoming and northern Colorado alone, the beetle’s population has affected more than four million acres of trees in Medicine Bow-Routt National Forest and Thunder Basin National Grassland. “What really caused that mortality is the mountain pine beetle,” U.S. Forest Service Public Affairs Specialist Larry Sandoval said. “The beetle is a naturally occurring insect to the lodge pole pine ecosystem. But when trees are stressed by things like drought, they are more susceptible to things like beetles.” The beetle outbreak was brought on by three major factors, according to the U.S. Forest Service. A decade-long drought parched lodgepole pine in the region; warmer winters failed to freeze beetles during reproduction cycles; and this century’s firefighting efforts so successfully suppressed forest fires that most lodgepole pines in the region are largely the same age. “The age diversity problem is the greatest thing for us to learn moving forward with management of the forest,” Sandoval said. Lodgepole pine age distribution in the region is skewed toward the elderly; Sandoval said roughly 80 percent of lodgepole pines in Medicine Bow National Forest are between 75 and 150 years old. Thesemature trees are prime pickings for the beetle. “A lot of (the age diversity problem) can be put back to the tie-hack era,” Sandoval said. “With the building of the railroads, a lot of the lumber and timber came from this forest.” High demand for railroad lumber prompted massive forest clear-cutting in the early 1900s, while clear-cutting in post-tie-hack era forest management has been relatively rare. And with 20th century firefighting efforts mainly concentrating on suppressing even natural, lightningignited blazes, the forest has had little chance to thin its massive overgrowth of mature lodgepole pine. Recent warmer winters also contributed to the beetle epidemic, according to Steve Loose, wildlife biologist with the U.S. Forest Service. “Another contributing factor was no winters with extreme cold the last several years,” Loose said. “Several days of extreme cold can kill the beetle larvae.”
Extreme cold can reduce Mountain Pine Beetle populations, according to a Colorado State University study. For beetles to be killed during winter seasons, temperatures much reach 30 degreesbelow zero for at least five consecutive days. Along with consistent drought and the lack of age diversity among lodgepole pine, the ongoing beetle epidemic has led to what the Forest Service now calls the “perfect storm” for today’s massive forest death. “The perfect storm has three factors: the beetle’s epidemic numbers, a decade-long drought and age class distribution,” Sandoval said. This massforest death creates a slew of safety concerns for the region. Falling trees pose threats to life and can damage property; the Forest Service estimates up to 100,000dead trees fall to the ground every day in southern Wyoming and northern Colorado. Fallen dead trees quickly become hazardous fuel for wildfires. “Of course, a forest full of dead, beetle-killed trees is definitely going to be more primed and ready to burn,” Sandoval said. “If we didn’t have a drought situation going on, green trees are going to be in a condition to fare better (in the caseof a wildfire).” Already this summer season, wildfires have scorched nearly 150,000acres across the state of Wyoming. Currently, Albany County’s Squirrel Creek fire is burning on 7,000acres of mostly beetle-killed forest, according to InciWeb.org updates. The Mountain Pine Beetle is naturally a part of the region’s ecosystem, and in regular populations does not pose a considerable threat to a forest’s health. In outbreak situation like today’s, however, natural predators like woodpeckers and other insects often fail to prevent widespread beetle attacks.