Drought, disease and insects killed 36 million trees across California in 2022

A group of conservationists survey several properties in search of the goldspotted oak borer in 2022 in Oak Grove.
A group of conservationists, community members and an arborist survey several properties in search of the goldspotted oak borer in on Friday, Dec. 9, 2022 in Oak Grove, California. In recent years, the insect has killed many of the community’s oak trees.
(Ana Ramirez/The San Diego Union-Tribune)

Federal officials fear tree mortality could help drive mega blazes. Hundreds of millions of dollars are now slated to thin out forests across the West.


More than 36 million trees died across California last year, including 90,000 trees in Southern California’s four national forests, officials announced Tuesday, Feb. 7.

The central Sierra Nevada and areas north were hit the hardest, according to aerial surveys conducted by the U.S. Forest Service across federal, state and private lands.

Mortality was up significantly from 9.5 million dead trees in 2021, as a result of ongoing drought, disease and insects, such as pine and fir engraver beetles, officials said. Overcrowding of forests, as the result of a century of aggressive wildfire suppression, has exacerbated these impacts as trees competed for limited moisture.

Despite recent storms, tree mortality is predicted to remain elevated until the state experiences several consecutive years of normal precipitation, officials said. About 150 million trees died across the state over the last decade, including about 89 million in 2016 and 2017 during a period of severe drought.

Many researchers fear that a perfect storm of drought, overly dense forests and tree mortality has set the stage for highly destructive mega blazes, such as the 2020 Creek fire in Fresno and Madera counties.

President Joe Biden announced last year a 10-year plan to roughly quadruple the federal government’s efforts to thin out wildfire-prone landscapes across the West, using chainsaws, heavy equipment and prescribed fire.

“Forest health is a top priority for the Forest Service,” Jennifer Eberlien, regional forester for the Pacific Southwest Region, said in a statement. “The agency’s 10-year strategy to address the wildfire crisis includes removal of dead and dying trees in the places where it poses the most immediate threats to communities.”

Southern California has struggled to chop back forests in the name of wildfire prevention, according to a Union-Tribune analysis. The Biden administration now plans to dole out $10 million to ramp up such efforts across the region.

Jan. 22, 2023

The primary goal of thinning a forest is to prevent wildfires from jumping into treetops, where flames can spread rapidly and engulf entire stands. That’s how the 2003 Cedar fire wiped out roughly 95 percent of the trees in Cuyamaca Rancho State Park.

“Working together, we can mitigate the risks of tree mortality and high-intensity wildfire by reducing the overabundance of living trees on the landscape,” Eberlien said.

About $131 million was allocated last year to projects across California, Arizona, New Mexico, Colorado, Montana, Idaho, Oregon and Washington. This year, the federal government aims to dole out another nearly $930 million to treat fire-prone landscapes across those states, as well as in Utah and Nevada.

The most recent round of funding includes $10 million to chop back forests across Southern California with a goal of treating 27,500 acres over the next three years.

San Diego County, which has a relatively small amount of conifer and oak forest, saw 9,400 trees die across 1,800 acres last year. The primary culprit was the goldspotted oak borer.

“The most widespread area of mortality occurred south of Palomar Mountain,” said Nathan Judy, spokesperson for the Cleveland National Forest. “We are working with federal, state, and local partners in our communities to plan and implement hazard tree mitigation projects.”