Drought and bark beetle kill millions of trees, increase wildfire risk in North State forests

The bark beetle infestation that decimated large swaths of forest in the southern Sierra Nevada has moved into the North State, killing millions of trees and adding fuel to an already dangerous fire season.

And the problem isn’t likely to go away anytime soon, according to the U.S. Forest Service, the federal agency responsible for managing much of the forested land in California.

While officials with the Redding-based Shasta-Trinity National Forest try to stem the growing threat of tree die-offs, they say it may be more of a challenge than they can handle.

“What we have ahead of us, what we have in front of us, we can't get ahead of. Not the way we're staffed,” said Todd Hamilton, a silviculturist with the national forest.

The ongoing drought throughout the West has made North State forests more susceptible to the beetles, according to the forest service.

From 2010 to 2019, more than 163 million trees in California’s forests were killed, mostly by bark beetles, with the hardest-hit areas in the southern Sierra Nevada, according to the forest service.

A 2019 forest service survey showed more than 3.7 million trees killed in just three North State national forests: the Lassen, Klamath and Shasta-Trinity.

During a recent tour of the Gilman Road area, Hamilton pointed to a stand of beetle-killed trees near Lake Shasta, noting those trees will eventually rot and fall, creating a fire hazard.

'Just waiting to go up in flames'

“You have downed logs, more vegetation is going to grow and if you do get a fire in there again, or when,…” Hamilton said.

“It's gonna burn really hot and be very hazardous to any kind of firefighting resources you put in there,” Joe Stubbendick, a Shasta-Trinity recreation officer said, finishing Hamilton’s sentence.

The area of dead trees Hamilton pointed out grew not far from where the Salt Fire broke out at the end of last month. The blaze continues to burn, consuming thousands of acres of dense forest.

A California Department of Forestry and Fire Protection paper on the bark beetle says the damage from the insects poses a serious fire threat.

“In some communities, up to 85 percent of the forest trees have been killed, becoming dry fuel, just waiting to go up in flames,” the Cal Fire paper says.

The 2019 forest service aerial survey of tree mortality shows the Klamath National Forest, with large swaths of land in Siskiyou County, was the forest hit hardest in the state, with an estimated 1.8 million dead trees.

Here is a breakdown by county of tree mortality in the North State, according to the survey:

• Shasta: 305,000 trees on 115,000 acres
• Siskiyou: 2.8 million trees on 406,000 acres
• Tehama: 318,000 trees on 67,000 acres
• Trinity: 1 million trees on 150,000 acres

What the drought does to an overgrown forest

The beetle is a tiny insect, about the size of a match head, but the sheer numbers pose a risk to the forest, officials say. They lay much of the bark beetle problem on forests that have become too overgrown with small trees and brush.

And ironically, it’s decades of aggressive fire suppression that has left forests dense and overcrowded, according to the forest service.

A hundred years ago, low intensity fires regularly burned through the forests, keeping stands of trees thinned out, and prevented them from becoming too thick.

Because smaller trees were regularly thinned out by fire, the trees that remained were larger and spaced farther apart.

A hundred years ago, a forest would have typically 20 or 30 trees per acre, Hamilton said. Nowadays, though, it is not uncommon to have 800 to 1,000 smaller trees an acre, he said.

When a drought comes along, like the current one, too many trees are competing for too little moisture and the trees’ natural defense against bark beetles breaks down, he said.

When trees are healthy and they get plenty of moisture, they exude sticky sap to ward off the bugs and protect themselves.

But when trees lack water they can’t produce enough sap, and the beetles move in and damage trees until they die, Hamilton said.

"When bark beetles’ population is at epidemic levels they can still attack and overcome even healthy trees," according to Cal Fire.

Over the past couple years, as the drought dragged on, conditions for bark beetles have improved.

June in the North State was one of the hottest and driest on record. The number of days over 100 degrees tied a record for the month, and less than an inch of rain fell during the 30-day period.

The annual rainfall total for the year remains less than 50% of normal, and in the second year of a prolonged dry period, the North State is in an “exceptional drought,” the U.S. Drought Monitor’s most severe level.

That concerns Eric Knapp, a research ecologist with the forest service’s Pacific Southwest Research Station.

“With the tree mortality already picking up steam, I am especially nervous about what the future holds this summer, especially after the very hot June we’ve experienced. Trees are already stressed, and we have at least three and maybe four more months without rain ahead,” Knapp said in an email.

“I wouldn’t be at all surprised if we see an outbreak on par with what happened in the central and southern Sierra between 2013 and 2017. There are just too many trees without enough water to support them, and trees in a weakened state just can’t defend themselves against bark beetles,” he said.

Forest thinning effective in slowing down a pest

The best defense against the beetles appears to be thinning out areas of the forest to reduce competition for scarce water resources, forest officials said.

PHOTOS: Salt Fire north of Redding burns forest; forces evacuations

But removing all the beetle-infested trees and thinning large swaths of the forest would require more staffing than the Shasta-Trinity has, so officials are prioritizing which areas they can treat.

They plan to focus on thinning developed areas where people live and work and around other infrastructure such as roads, power lines and recreation sites, said Stubbendick.

The Shasta-Trinity already burns thousands of acres annually to thin out the forest of small trees and brush to reduce fire danger, Hamilton said.

Near the end of 2019 the forest service closed down the Hirz Campground on the McCloud River arm of Lake Shasta because of a bark beetle infestation.

Forest service officials cut down some 600 trees to thin out a 35-acre area. The campground was supposed to open July 4th weekend this month, but that was delayed due to the Salt Fire burning nearby.

Knapp said he published a research paper earlier this year that shows forest thinning slows bark beetle damage.

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The research compared tree mortality on adjacent plots of land in the Stanislaus National Forest, with one parcel thinned out and the other left untouched, he said.

There was a “stark” difference in higher tree mortality on the plot that was not thinned, he said.

“It shows you that you can really change the outcome just by reducing competition and increasing the amount of water for each tree,” Knapp said.

Hamilton said most of the trees dying on the Shasta-Trinity National Forest are in the area around Lake Shasta in the 1,000 to 2,000-foot elevation.

They are, however, finding more beetle damage in Trinity County, he said. The beetles also tend to skip over the trees forest officials value less, Hamilton said.

“And it just so happens, it's not the small trees that are dying. It's the large ones that we value probably the most,” Hamilton said.

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Damon Arthur is the Record Searchlight’s resources and environment reporter. He is among the first on the scene at breaking news incidents, reporting real time on Twitter at @damonarthur_RS. Damon is part of a dedicated team of journalists who investigate wrongdoing and find the unheard voices to tell the stories of the North State. He welcomes story tips at 530-338-8834 and damon.arthur@redding.com. Help local journalism thrive by subscribing today!