Millions Of California Trees Were Lost To Drought. Will Two Wet Winters Help Repair Our Forests?

Over the past decade or so, California’s forests took a beating as more than 170 million trees died, many weakened by drought and extreme heat, and killed off by beetles and disease. Others were destroyed by fires.

Now that we have two wet winters on the books, soils are saturated, the snowpack is sufficiently dense and we may start to see some decent recovery.

“I expect to see a pretty dramatic decrease in fir mortality and conifer mortality overall this year due to nice precipitation years back to back,” said Jeffrey Moore, who’s been documenting California’s tree mortality from the air since 2009, as the aerial detection survey program manager for the U. S. Forest Service. He’ll begin performing the 2024 survey in July.

Thousands of pine trees around Tahoe lake died, as seen on August 10, 2022.

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George Rose

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Getty Images North America

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How we got here

During his first couple of years in the role Moore generally recorded about 500,000 dead trees annually. But when the drought years took hold, the death count climbed.

Lower elevation conifers in the southern Sierra were particularly hard hit between 2012 and 2016, while higher elevation fir in the central and northern parts of California suffered between 2020 and 2023.

The worst year was 2016, with more than 65 million trees recorded dead.

“Once a tree has been compromised due to drought, it can't just bounce back 100% right away, but after two years of good precipitation, I think most of the surviving trees will be in good enough shape to defend themselves against the bark beetle populations that are out there on the landscape,” he said.

A firefighter cools a burning tree at the Oak Fire near Midpines, northeast of Mariposa, California, on July 23, 2022.

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David McNew

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AFP

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The threat of dead trees

The upside to some of the tree death and fires is that they've helped thin out long overcrowded forests, the result of more than a century of fire suppression.

With more resources available to the surviving trees, there's the possibility that some of our forests could end up more resilient in the long run if managed correctly with techniques like prescribed fire.

However, the trees that are recovering nicely are still at risk, especially if they're in the middle of a whole bunch of dead trees, which supercharge fires when they blow through. That's something we explored in depth in our wildfire podcast The Big Burn.

Because of the amount of precipitation we've gotten, fire season could be delayed until July or August in our forests, according to Jonathan O'Brien, meteorologist with the U.S. Forest Service.