California losing 2 million trees a month as drought-related plague drags on

Dead trees dot private lands just outside Sequoia National Park. The U.S. Forest Service announced Monday that California’s tree die-off continues even though the drought is over. Dead trees dot private lands just outside Sequoia National Park. The U.S. Forest Service announced Monday that California’s tree die-off continues even though the drought is over. Photo: Leah Millis, The Chronicle Buy photo Photo: Leah Millis, The Chronicle Image 1 of / 32 Caption Close California losing 2 million trees a month as drought-related plague drags on 1 / 32 Back to Gallery

California’s forests are seeing a continued die-off of trees even a year after last year’s heavy rains ended the state’s crippling drought.

The U.S. Forest Service announced Monday that 27 million trees died over the past 13 months after five dry years left them severely dehydrated and vulnerable to bark beetle attack.

The unprecedented casualties, which run rampant across the Sierra Nevada as well as parts of the coast, have turned patches of forest into a somber rust color for mile after mile. The mortality is so great in some places that foresters have closed roads and campgrounds for fear of the dried-out, lifeless trees falling on people. Tourists to Yosemite and Sequoia national parks, meanwhile, have been stunned by the unexpectedly grim views.

State officials also worry about dead groves becoming easy tinder for the lethal wildfires that have plagued California in recent years. Efforts to remove hazardous stands have been slow due to the sheer volume of death.

An estimated 129 million trees across some 8.9 million acres have died since 2010, according to the Forest Service.

“It is apparent from our survey flights this year that California’s trees have not yet recovered from the drought,” said Randy Moore, a forester at the Forest Service’s Pacific Southwest Region office. “The Forest Service will continue to focus on mitigating hazard trees and thinning overly dense forests so they are healthier and better able to survive stressers like this in the future.”

Federal foresters alongside state and local land management agencies and state utilities have removed an estimated 860,000 dead trees since the drought began. Crews have prioritized stands near communities and along roads.

As bad as the die-off is, Forest Service records suggest it may be slowing. The death toll over the past year is less than half of 2016’s — when more than 60 million trees fell prey to drought and bark beetles.

Last winter brought near record rainfall to many parts of the state, providing welcome relief for many stands.

The upshot of the vast tree loss remains a matter of debate. Some scientists worry that the casualties may mark the beginning of a downward spiral for California’s forests as the changing climate promises longer, more intense droughts. Trees, they say, will eventually be replaced by hardier shrubs and grasslands.

Others, though, say that die-offs are natural to forests. They allow weakened woodlands to be replaced by a sturdier crop of trees and ultimately provide a healthier habitat for a whole host of wildlife.

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexaner