Why Are California’s Trees Dying?

California’s iconic mountain forests are in serious trouble, according to a series of recent studies. The latest — an aerial survey of the state’s most forested regions — shows that a combination of drought and insect damage wiped out a startling 36 million trees between 2021 and 2022.

“These last three years have been the hardest, driest three years on record in California,” said Jeffrey Moore, a forester with the U.S. Forest Service and the lead researcher on the survey, which was conducted from July to October. “When you get talking about multiyear exceptional drought, I mean, it’s rough on everything.”

The death toll wasn’t the highest we’ve seen in recent years, but it was troubling because of the type of trees that died and where they were. There are perhaps 40 species of native evergreen species in California, but more than three-quarters of the dead trees detected last year came from one family: firs.

These Christmas-tree-looking conifers are found mostly at higher elevations where there’s more snow. Half of the dead trees in the study were red firs, a crucial alpine tree in places like the Lake Tahoe area, which had avoided the worst effects of the drought until now.

Likewise, the Douglas fir had resisted the drought by using its deep roots to pull up water. But last year saw a shocking 16 times more dead Douglas firs than the previous one. In other words, the trees that should be the most able to survive the drought are now dying in large numbers.

“Doug fir is probably one of the most resilient species in the Sierra Nevada,” said Scott Stephens, a forestry professor at the University of California, Berkeley. “It is the last species that actually has not been really significantly impacted.”

Losing so many mature, drought-resistant trees can be devastating to delicate mountain ecosystems, and it indicates that the forests of the Sierra cannot withstand many more dry winters. And, of course, all of those dead trees may become a fire hazard. A study from last July showed California had lost an area of forest land nearly the size of Delaware since 1985, largely from wildfires.

What’s causing this die off? In effect, it’s a one-two-three punch, Stephens said. First, over the last 100 years, California forests have gotten more crowded, thanks to policies like fire suppression. He and several colleagues recently showed that 60 percent of lower pine forests in the Sierras are so crowded, the trees are essentially choking one another for water and nutrients.

Then came drought. The already thirsty trees reached a breaking point and many started to die. Lastly, pests like the fir engraver beetle arrived and made a meal out of the already desperate trees.

Stephens said California needed to begin managing its forests preemptively to withstand drought. The best way to do this, he said, is selectively thinning out smaller trees and clearing dead ones before they become a fire risk.

It’s not all bad news though. For one thing, about a third of the dead trees from the U.S. Forest Service survey were white firs, which are the forest version of garden weeds. They grow fast and push out trees like red firs that create a healthier ecosystem. With them gone, it’s possible other species might have a better chance.

Also, there has been a lot of snow this winter in the Sierras, which means the remaining trees will soon be healthier and better able to fight off pests. But Moore said he’s ready for at least one more bad year, since many of the trees that died last summer, including oaks in the lower elevations, weren’t spotted by the last aerial survey, because they hadn’t turned brown yet.

Stephens said: “We’re quite fortunate this year that we were able to recharge the soils. We’ll have to watch, but it’s certainly better than being another drought year.”

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Where we’re traveling

Today’s tip comes from Will Tait, who lives in Emeryville. Will recommends planning a summer trip to Golden Gate Park in San Francisco:

“July, August and September finds a most glorious show of dahlias in the Dahlia Garden in Golden Gate Park. Hundreds of plants each boasting many flowers; photographs do not begin to do it justice.

I have been making the pilgrimage for many years and am always delighted. A short drive out to where the park meets the ocean, one can have lunch overlooking the water at the Beach Chalet Brewery and Restaurant.”

Tell us about your favorite places to visit in California. Email your suggestions to CAtoday@nytimes.com. We’ll be sharing more in upcoming editions of the newsletter.

Tell us

With Valentine’s Day coming up, we’re asking about love: not who you love, but what you love about your corner of California.

Email us a love letter to your California city, neighborhood or region — or to the Golden State as a whole — and we may share it in an upcoming newsletter. You can reach the team at CAtoday@nytimes.com.

And before you go, some good news

Harish Srikar Vemuri and Princess Daisy Martekie Abla Akita started dating in their third year at Harvard Law School, in 2019.

Back then, the couple, who now lives in Santa Monica, didn’t know that the negotiating skills they acquired there would come in handy for wedding planning.

The two, both 31, found themselves not only dealing with their Indian and Ghanaian families, and all their traditions and dietary needs, but also staying true to their own modern, egalitarian partnership. “This past year has been a lesson in international diplomacy,” Akita said.

Vemuri wanted a wedding in India so his grandparents could attend, while Akita’s parents wanted to host something in her native Ghana. But some of their close friends couldn’t travel to either place. To make it all work, they ended up having four separate wedding ceremonies on three continents.

Read more in The Times.

Thanks for reading. We’ll be back on Monday. Enjoy your weekend.

P.S. Here’s today’s Mini Crossword.

Soumya Karlamangla, Isabella Grullón and Allison Honors contributed to California Today. You can reach the team at CAtoday@nytimes.com.

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