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Drought, Beetles Preying on Weakened California Forests

Sacramento Bee: At least 12 million drought-weakened trees have died across California as forest officials conduct more aerial surveys.

Written by Ryan Sabalow Published on Read time Approx. 4 minutes

Frank Cody wasn’t surprised to learn that at least 12 million trees across California recently have died from a lethal mix of bugs and long-term drought. Business is booming for the South Lake Tahoe tree service business owner.

“We’re close to halfway through the season, at least for Tahoe, and we’ve done as many dead trees already this year as we do in an average year,” he said. “We’re seeing a lot of trees dying.”

Four years of drought have put an incredible strain on California’s forests – particularly stands of pine and fir. The problem is more pronounced in Southern and Central California, but foresters say it’s spreading north.

The reason trees are dying is simple enough. In many areas, there’s not enough water for the tree roots to suck up. Weakened, the needle-covered trees are unable to secrete the sticky resin to fight off bark beetle infestations. Mild winters also don’t kill off as many of the bugs, which burrow under bark and into the trees’ soft insides – which their larvae feed on.

Foresters and researchers say tree mortality is a problem that’s likely to become more common as California grows hotter and drier due to global climate change.

“This is going to be big,” said William Anderegg, a Princeton University researcher who studies climate change and forests. “This is going to have a big impact on forests, and it’s probable that these numbers – the 12 million – are just the tip of the iceberg.”

This week, teams of researchers with the U.S. Forest Service continued survey flights looking for stands of dead timber. John Heil, a Forest Service spokesperson, said the crews will be flying over low elevations with an eye on pine and mixed conifer forests. He said the surveyors may travel as far north as the Shasta-Trinity National Forest.

In April, similar surveys showed staggering numbers of dead or dying trees in Southern and Central California. The researchers flew over more than 8.4 million acres of public and private forest lands. They spotted nearly 1 million acres of ponderosa, gray and pinyon pine stands that had turned red, a sign they were dead or dying.

While flying over the foothills, the researchers also reported some stands of blue and live oak that appeared dead, though it was unclear whether they’d merely shed their leaves due to the drought.

Some of the worst pine die-offs are in the Sierra and Sequoia National Forests. This year, surveyors believe western pine beetles have ravaged a combined 6 million trees there. Last year, surveyors discovered only about 300,000 dead trees in those forests.

Steve Anderson, a resource officer for the Sequoia National Forest’s Kern River Ranger District, said in some stands there are about 10 to 15 red, brittle trees per acre.

“It definitely stands out,” Anderson said. “But what you don’t see are the gray trees from last year that kind of faded into the background.”

Don Owen, an insect scientist and forest health specialist with the California Department of Forestry and Fire Protection, said the beetle-killed trees are exposing problems with how California’s woods have been managed.

He said many forests have become unnaturally thick with undergrowth and small trees that otherwise would have been burned out by naturally occurring, low-intensity fires.

Without logging to thin out the woods or allowing wildfires to burn through the unnaturally thick and increasingly dry stands of trees, Owen said, there’s going to continue to be too many roots trying to suck up a finite amount of water.

“When there are too many of them,” Owen said, “it just compounds the problem.”

Because forests have been particularly dry in Central and Southern California, they’ve suffered the worst beetle infestations. Owen said that if the drought lingers, the infestations are likely to expand north.

So far, beetle-killed woods north of Yosemite are few and far between, said Mark Pawlicki, a spokesperson for the Anderson-based Sierra Pacific Industries, which owns 1.9 million acres of timberland in Northern California and Washington.

Pawlicki said there are pockets of beetle-killed trees in the private forests, which the timber company removes as quickly as possible to bring them to the mill.

“It’s an expensive proposition to get them,” he said. “But (we) do take them out to save their value.”

It’s aesthetics and not timber values that are foremost in the minds of the clients who hire Cody, the South Lake Tahoe tree service owner.

He said that he’s seen bark beetles in Tahoe’s pines and firs. But he reminds clients it’s not always the beetles’ fault for those ugly, dead trees on their lands. Rather, he tells them it’s a side effect of living in a populated area that, understandably, has been spared from wildfire. Their woods, he says, are too dense to thrive in the drought.

“Bark beetles get a bad name, but a lot of the time they’re just the final thing that finishes off an unhealthy situation,” Cody said. “That’s just nature limiting how many trees are growing in an area.”

This story originally appeared in the Sacramento Bee on July 10, 2015. To see more stories in the Bee’s ongoing coverage of the California drought, go to

Photo courtesy of Randy Pench, Sacramento Bee

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