Voracious Beetles Take Toll on Sierra Trees

Los Angeles Times
July 22, 1989


East of U.S. 50, where it climbs away from Lake Tahoe, an eyeful of distant ridges covered in a soft green carpet of pine and fir trees has served up a visual treat to many summertime motorists in the Sierra Nevada. Splotches of reddish-brown stain the vista this summer, dabbed on the green background as haphazardly as on a painter's dropcloth.

It is the burnt-red color of dead trees, and it can be found dappled on nearly all the evergreen forests of the Sierra range and Southern California. The loss of more than a million trees -- the state's worst die-off in more than a decade -- is a stark visual reminder that arid California has just come through three straight winters of thin snowpack and disappointing rainfall. The dead trees represent enough lumber to build 300,000 new houses and more are being discovered every day, the U.S. Forest Service says.

Scarcity of water itself is not killing the trees, which have withstood worse droughts in California's erratic meteorological history. The trees were weakened by lack of water, then finished off by a opportunistic epidemic of burrowing, mating bark beetles that foresters are powerless to stop. "It's certainly the worst I've seen in 13 years with the forest," said John Wenz, a Forest Service entomologist for the El Dorado and Stanislaus national forests, which include most of the high mountains from the south shore of Lake Tahoe to beyond Yosemite.

Here in the El Dorado, the hardest-hit forest of the Sierra range, the rising toll from bark beetles prompts daily queries to rangers from campers and other vacationers concerned or curious about all the sickly looking trees. Forestry officials are mainly concerned, however, that all the dry, rotting wood will be fuel for wildfires and that it represents a waste of usable timber. Beetles are also spreading onto private lands at lower elevations and even claiming yard trees in mountain towns. "You can drive out of Sonora and see red trees everywhere," said Steve Waterman, spokesman for the Stanislaus National Forest.

Concern is not the same as surprise, however. Bark beetles are native to the state's woodlands, and flourish almost every time there is a drought of consequence like the current dry period, which finally eased somewhat with a final wave of storms last winter. "This was not unexpected," Waterman said.

Nor is there any official fear that the forests will be decimated, although the damage could mount as high as in the last major epidemic of beetles during the major drought in 1976-1977. Enough trees died over four years from that infestation to supply about 13 billion board feet of lumber, enough for more than a million new homes, said John Neisess, the Forest Service's pest control expert in California. This year's toll is expected to top 4 billion board feet, he said, and will keep mounting next year.

"That's more timber being killed by bark beetles than we (the Forest Service) offer for sale in a year," Neisess said. "That's also more than was burned in 1987" -- when woodland fires swept the state and devastated the Stanislaus National Forest near Yosemite National Park.

Bark beetles bore into fir, pine and cedar trees, where they lay their eggs. Healthy trees can repel the attack by flooding the beetles' egg galleries with pitch, pushing the pests and their larva back out of the bark. But trees in distress from lack of water cannot spare enough sap to expel the pests, foresters say. "The sap is their only defense," Neisess said.

Some trees succumb from having their bark girdled, others from a fungus the beetles carry that grows into the sapwood and blocks moisture from moving up the trunk. The fungus stains the inner wood blue, which can render the wood less valuable to lumber mills.

Forest Service officials said salvagers will try to remove tens of thousands of the dead trees, but the job is complicated by the erratic infestation of the beetles. The dead trees are scattered across all elevations of the timberlands, often in stands of one or two Ponderosa or sugar pines surrounded by acres of healthy, green trees.

Most of the dead trees are far from roads and outside of forest areas that were scheduled for timber cutting by loggers. In some cases helicopters will be used to ferry the trees to roads where they can be trucked to lumber and pulp mills.

Trees found in more remote wilderness will be left untouched, since it is policy to leave those areas as close to their natural state as possible. Some affected trees will also be left behind as a natural replenishment of forest snags, the dead trunks and limbs used for nesting and feeding by many species of animals. "We need these periodic waves of mortality to create new snags," said Jane LaBoa, silviculturist for the Tahoe National Forest.

With such a huge amount of timber involved, routine tree harvesting by loggers is being delayed and in some areas postponed for the year because foresters are busy conducting environmental studies required before salvage can begin, Forest Service spokesmen say. But lumber mills are not unhappy since the salvage may make up for some of the timber that won't be cut down this year because of concerns over the survival of the northern spotted owl.

However, the dead trees must be collected swiftly or they begin to lose their value to mills. Dead pines can be left in the forest up to two years and still retain their timber value, but white firs -- a large share of the affected trees -- need to be cut down and brought out of the forest within a year, foresters say.

The worst die-off in the Sierra range is south of U.S. 50, the main link between South Lake Tahoe and Sacramento. Most of the timber taken there from the central Sierra goes to mills that chop it into chips for building materials or use the pulp for cardboard. Some also is burned in co-generation power plants.

Coastal forests and those farther north have not suffered as severely from the beetle infestation except for isolated spots, such as the Plumas National Forest on the east side of the Sierra range near Lassen National Park. The beetles have also not become a problem outside of California, forestry officials say.

© Los Angeles Times 1989