Bark Beetles Kill Millions of Acres of Trees in West
The New York Times,
"We're seeing exponential growth of the infestation," said Clint Kyhl, director of a Forest Service incident management team in Laramie, Wyo., that was set up to deal with the threat of fire from dead forests. Increased construction of homes in forest areas over the last 20 years makes the problem worse.
In the next three to five years, Mr. Kyhl said, virtually all of
Foresters say the historic outbreak has several causes. Because fires have been suppressed for so long, all forests are roughly the same age, and the trees are big enough to be susceptible to beetles. A decade of drought has weakened the trees. And hard winters have softened, which allows the beetles to flourish and expand their range.
Hoping to keep their forests from completely dying, to earn money by selling dead and infected trees and to mitigate fire risks, landowners are scrambling to cut the pines. If enough are cut -- up to 75 percent -- it might leave some behind that, with less competition for water, can survive. Still, for many landowners, cutting most of the forest where they have they built their homes is painful. "I've literally had people in my office crying," said Gary Ellingson, a forestry consultant for Northwest Management.
The black, hard-shelled beetle, the size of a fingertip, drills through pine bark and digs a gallery in the wood where it lays its eggs. When the larvae hatch under the bark, they eat the sweet, rich cambium layer that provides nutrients to the tree. They also inject a fungus to stop the tree from moving sap, which could drown the larvae. That fungus stains the wood blue.
"The Latin name is Dendroctunus, which means tree killer," said Gregg DeNitto, a Forest Service entomologist in
To fend off the bugs, trees emit white resin, which looks like candle wax, into the beetles drill hole. Sometimes the tree wins and entombs the beetle. Often, though, the attacker puts out a pheromone-based call for reinforcements and more of the beetles swarm the tree. In a drought the tree has trouble producing enough resin, and is overwhelmed.
There are some defenses. Owners nail to a tree an "aggregator pheromone" in a small packet, which mimics the chemical scent given off by beetles when a tree is full of insects. It can work when beetles are not too numerous, but at some point the beetles are not deterred.
Large, old, high-value trees, ones that shade campgrounds or yards, can be sprayed with an insecticide. But the trees need to be sprayed from the base to the height at which it is less than 4 inches around. Each tree costs about $10 to $15 if hundreds are sprayed.
Lodgepole pines are largely confined to high altitudes. But the beetles have moved into ponderosa pine forests on
The beetles will only be truly checked, experts say, if temperatures that used to reach 30 and 40 below for weeks return to the
The death of the forests worries the tourism industry. Many ski areas have cut down their forests because of the hazard of falling trees and have revegetated the land.
At Vail Ski Resort, for example, which has been particularly hard hit, workers have removed thousands of dead trees and planted new ones.
The dead trees that blanket the mountains are shifting ecosystems as well. In Yellowstone, for example, the beetles are killing the white-barked pine trees, which grow nuts rich in fat that are critical to grizzly bears in the fall. Biologists in Canada say streams will flash-flood because live trees will no longer catch snow and allow it to slowly melt, and it could injure salmon and destroy habitat. On the other hand, woodpeckers and other insect eaters will thrive.
Wildfire is the biggest threat. Some towns like Steamboat Springs and Vail, Colo., are surrounded by dead forests, and the Forest Service and logging companies are clear-cutting "defensible space" so firefighters have a place to fight fires.
After the trees die, the risk of crown fires that move through the canopy is the threat. After four or five years, as the dead trees fall to the ground, the threat of catastrophic fire is most severe. Fires in the piles of logs severely damage soils, prevent regrowth and cause mudslides.
Rainfall on damaged ground could also lead to widespread mudslides and silt buildup in rivers and reservoirs, which many mountain communities depend on for water. Strontia Springs Reservoir, a main water source for
The other major problem is large numbers of falling trees. In
But there is a lot more to do. We know they are going to fall, Mr. Kyhl said. And they are going to fall in the next 10 to 15 years. Theres campgrounds, thousands of miles of road, picnic areas, power lines and trails. How do we keep the facilities open for people to use?
The agency is faced with clearing a strip of 75 to 100 feet of dead trees along highways so they are not closed by blow downs.
Then there is a question of what do with the wood. Sawmills have diminished in the West in recent years, and there are not enough mills to take all of the timber.
Some trees are being shredded for use in biomass boilers, and carpenters are using the pine stained blue from the fungus for furniture.
Still, the volume of timber used is small compared with the vast acreage of dead trees.
The West that depends on tourism, meanwhile, wonders what their customers will think about the dramatic change in scenery. Four million visitors a year come for sightseeing and recreation to
Copyright 2008 The New York Times Company