Extreme drought and hot weather killed millions of trees in California’s forests last year, according to a new report from the U.S. Forest Service.
Aerial surveys conducted from July 2022 to October 2022 surveyed 39.6 million acres (over 61,000 square miles) of tree canopy across California. The Forest Service found about 2.6 million acres (over 3,100 square miles) of dead trees, or the equivalent of about 36.3 million dead trees.
The tens of millions of dead trees tell a story of how bad the dry and hot conditions were across the American West throughout much of 2022. The average mortality was a lot higher last year than in 2021, the report explained. The survey looked at a large variety of trees to assess which were the most affected. Douglas fir mortality especially increased in 2022 from 2021. In 2021, an estimated 170,000 Douglas firs died—that number jumped to around 3 million. This represents a 1,650% increase in mortality from one year to the next.
Lack of water, even for trees that don’t need all that much precipitation, has been a dire situation. Just this past November, large sections of Central and Northern California saw exceptional and extreme drought, according to the U.S. Drought Monitor. Prolonged drought doesn’t simply dry trees up; it makes them weaker, which makes them more susceptible to damage from insects that destroy the trees. Trees are usually attacked by bark beetles that lay their eggs in tree bark, and the larvae that hatch feed off the trees.
Ryan Tompkins, a forester and natural resources advisor at the University of California Cooperative Extension, told the LA Times that forest density in California makes things worse. “When these forests are really dense, trees are competing for a finite amount of water, particularly in a dry year,” he said. “While we see these periodic droughts, and these periodic tree mortality events, some of this is driven because we’ve normalized these very dense forests.”
Last year’s drought also affected forests farther up the West Coast. In December, the Columbia Insight reported how aerial surveys conducted by the Forest Service found huge patches of dead forest throughout Oregon and Washington. What was supposed to be miles and miles of evergreen trees was instead yellowing or brown.
The widespread drought conditions have only recently abated, after a series of several atmospheric rivers brought deadly storms to California from late December into mid-January. As of early February, California is no longer experiencing exceptional and extreme drought. The storms meant high levels of snowpack across the Sierra Nevada mountains at the beginning of this year, but officials have warned that the weather can quickly swing back into being especially dry. It’s too early to say if this year’s snowpack will contribute to more water in California this summer.