USA: As global warming rises, so do tree-killing infestations of bark beetles By Katherine Kerlin
04 April 2002
In Alaska’s Kincaid Park, just a 10-minute drive outside downtown Anchorage, the parking lot gives way to a path strewn withwildflowers, huge with the midnight sun’s constant attention. The trail winds past vistas of the Alaska Range rising behind Cook Inlet, and your chances for spotting a moose increase with the elevation. The trees tower as their needles exhale their woody scent. Interrupting this serene forest are pitiful patches of sagging, gray trees, defeated by the spruce bark beetle.
According to Ed Holsten, an entomologist with the U.S. Forest Service in Alaska, about 2 million acres of spruce forests were infested in Alaska between 1920 and 1990. Three million acres were infested during the 1990s alone, and the epidemic reached its peak of 1 million in 1996. The hardest hit was the Kenai Peninsula, where nearly 70 to 80 percent of the trees have been killed. Scientists attribute the epidemic not only to the mismanagement of forests, where crowded trees compete for light and nutrients, weakening their defenses against insects, but also to global warming. The Environmental Protection Agency (EPA) reports that the average temperature in Anchorage has increased 3.9 degrees Fahrenheit over the last century, and that by 2100, temperatures in Alaska could increase by five degrees in spring, summer, and fall and by 10 degrees in winter. “In Alaska, the distribution of plants and animals is controlled by climate,” said Holsten. “Any subtle change in temperature will affect insects. Spruce bark beetles usually have a two-year cycle, but warmer temperatures can cause them to complete their cycle in one year. So a lot more are being bred at one time.” Along with beetle infestations come forest fires. Michael Fastabend of the Kenai Borough’s Spruce Bark Beetle Mitigation Office, said that as dead trees drop needles and limbs, fuel and tinder accumulate on the ground, making conditions ripe for a fire. The EPA said the increase in forest fires due to beetle outbreaks and global warming “is of particular concern for wildlife species that make extensive use of mature and old-growth forests, such as martens, fishers, and caribou.” Holsten added red squirrels and the townsend warbler to that list but said some small mammals, such as mice and moles, thrive in affected areas where there are now fewer trees.
The federal government has allocated $10 million to the Kenai Borough and $2 million to Anchorage for forest regeneration and to protect communities from beetle-induced fires. “There is no outbreak anymore because the beetles have eaten themselves out of house and home,” said Holsten. “Now we’re just trying to pick up the pieces.” But Alaska is not alone in its beetle battle. The spruce bark beetle’s range stretches across North America, from the eastern United States through the Rocky Mountain region and up to Canada. A report from the Forest Service says spruce beetle outbreaks in Utah in the 1990s infested more than 122,000 acres and killed more than 3 million spruce trees. “In the past 25 years,” the report continues, “outbreaks have resulted in estimated losses of more than 25 million boardfeet in Montana, 31 million in Idaho, more than 100 million in Arizona, 2 billion in Alaska, and 3 billion in British Columbia.”
British Columbia is currently facing attack from the mountain pine beetle, another bark species. Like the spruce bark beetle, the mountain pine beetle is also indigenous to North America, global warming plays a hand in its infestation, and dead trees left after epidemics are a source of fuel that may cause wildfires unless removed. The beetle attacks and kills lodgepole, ponderosa, sugar,and western white pines, and outbreaks can kill millions of trees each year. British Columbia’s newly elected Premier Gordon Campbell said the beetle has infested $4.2 billion-worth of timber in the province’s west central interior, where more than 15 million acres, or twice the size of Vancouver Island, are affected. The Cariboo Lumber Manufacturers’ Association (CLMA) and the Northern Forest Products Association (NFPA) have joined to form the Mountain Pine Beetle Emergency Task Force to fight the epidemic. Working with the Ministry of Forestry and the Ministry of Environment, Lands, and Parks, the task force is trying to come up with a strategic plan for salvaging the forests and the economic stability of the area, which is highly dependent on the timber industry. The CLMA/NFPA reported that by the end of the 2000 to 2001 season, industry had spent more than $79 million fighting the beetle and the B.C. government had spent more than $18 million. “If left to run its course,” said the CLMA/NFPA, “water quality, riparian areas, wildlife habitat, and other environmental, visual, and recreational qualities can be negatively impacted. Millions of dollars in trees, forestry, and tourism jobs can be lost, and the long-term fiber supply that supports communities can be put at risk.” According to the U.S. Forest Service, a bark beetle leaves a tree once it has killed it, though larvae and adult beetles may still be under the bark during the first winter after infestation.This leaves the tree with three years of lumber value left. One beetle-control strategy for both Alaska and B.C. is moving logging operations into areas of beetle kill. Dan Rollert, woods manager with Weldwood Quesnel, said, “For every 100 infested trees we eliminate this year, we prevent 500 trees or more from being infested next year.”
Others, such as Paul George of the Western Canada Wilderness Committee, favor controlled burns over cutting infested areas, though most harvesters are required to replant. Measures such as silviculture and insecticides are also employed. But as Holsten said, “Noninvasive techniques like thinning stands are good to do in the beginning, but once you get an outbreak going, it’s like spitting into the wind.” Only cooler weather can stop the mountain pine beetleepidemic, said the CLMA/NFPA. As the high-noon moon of Alaska replaces summer’s 23 hours of sun and a chill returns to the forests, firefighters and trees alike receive a winter break from the hungry bark beetle. But if the warming trend continues, so will the potential for insects, fire, and loss of forests.