Ravaged by drought and bugs, North Coast forests prone to go up in flames
Thousands of trees in North Coast forests are dying, apparent victims of more than three years of drought and the bark-boring pests that flourish when water is scarce.
The dead and dying trees, mostly pines, are adding flammable fuel to forests where the fire risk is already high because of California’s prolonged drought. The dead wood won’t cause more fires, but once ignited, flames will burn hotter and be much more difficult to control, posing potential danger for rural residents and firefighters, fire officials say.
“It increases the intensity of the fire,” said Jim Wright, a Cal Fire division chief in Lake County, where most of the area’s dead trees have been found. “It’s just like starting a fire in your fireplace. It’s much easier to get a fire started when you have dry wood than green wood.”
The tree deaths are part of a larger, statewide problem that has ravaged the southern Sierra, where more than 10 million pine trees in national forests have perished. More than 12 million trees have died in national forests statewide in the past year because of drought and pests, according to U.S. Forest Service aerial surveys. Similar problems decimated pine forests in Colorado several years ago.
“Statewide, it’s horrific,” said Greg Giusti, forest adviser with the UC Davis Cooperative Extension.
Statistics for state and privately owned forests were not available, but Giusti estimates the tree deaths in Sonoma, Mendocino and Lake counties to be in the tens of thousands.
“It’s getting pretty impressive,” he said.
The trees are believed to have been weakened by the drought, then finished off by several different types of native bark beetles, which bore through the outer layers of trees to lay their eggs. The beetles and their larvae feed on the trees’ inner bark, damaging their nutrient-carrying circulatory systems. Healthy trees normally are able to limit infestations by releasing resin, also called pitch, that is toxic to many organisms, said Donald Owen, a Cal Fire entomologist and forest health specialist.
“When a tree is water- stressed or diseased, its ability to release pitch can decrease, thus making it more vulnerable to attack,” he said.
Once established, insect infestations expand as the invading bugs, releasing pheromones, attract additional beetles until they reach a lethal population level, Owen said.
If the insect populations continue to climb in an area, the creatures eventually are able to overwhelm healthy trees as well as those that are stressed, he said.
Locally, the hardest-hit area appears to be Lake County, including areas of Boggs Mountain State Forest, Cobb Mountain and Mount Konocti, where fall-like, red and brown colors are appearing in stands of conifer trees that normally remain green year round.
But drought-stressed trees also are dying in cities and among other types of tree stands, including eucalyptus in San Francisco’s Mount Sutro forest, said Giusti, who has been asked by UCSF officials to examine the trees.
Kurt Johnson, owner of a Ukiah-based tree-removal company, said he has been kept busy with calls to remove trees killed by drought and pests along the North Coast. His crews recently removed a half-dozen diseased conifers on one property on the city’s west side.
The forest conditions could alter firefighters’ tactics in what already has been deemed a high-risk fire season. Fire crews can’t battle flames in the tops of trees from the ground, and must rely on water and retardants dumped from aircraft and on clearings created to limit the spread of wildfire, Wright and other officials said.