The lethal combination of drought, heat and an infestation of ravenous bark beetles has killed 26 million trees in the Sierra Nevada since October, an “unprecedented” die-off that heightens an already high wildfire risk, officials said Wednesday.
The new estimate by the U.S. Forest Service brings the loss of trees to at least 66 million since 2010 — a problem that grew worse despite an average winter of rain and snow that brought some relief to urban Californians.
The dire report comes as fires have raged across California, burning thousands of acres, forcing evacuations and closing freeways.
“Tree dies-offs of this magnitude are unprecedented and increase the risk of catastrophic wildfires that puts property and lives at risk,” Agriculture Secretary Tom Vilsack said in a statement.
The latest estimates come from a May survey of six southern Sierra counties: Fresno, Kern, Madera, Mariposa, Tuolumne and Tulare. And the 26 million trees that apparently died between October 2015 and May continue a disturbing uptick.
Forest Service officials found 40 million dead trees between 2010 and 2015 and say that nearly 30 million of those succumbed to drought and insect mortality between September 2014 and October 2015.
The rapid recent die-off prompted Gov. Jerry Brown to declare a state of emergency in fall and form a tree mortality task force to help mobilize additional resources for the safe removal of dead and dying trees.
The Forest Service says it has felled over 77,000 hazardous trees to date. But the agency’s scientists say they expect to see continued high levels of tree mortality during 2016 in many areas. Officials said the Forest Service would conduct additional surveys throughout the summer and fall.
