How will climate change affect the giant sequoias in California?

There are a few things climate change could do, and are already likely doing to California’s majestic and massive sequoia trees, said Nathan Stephenson, a research ecologist with the United States Geological Survey who specializes in how climate change is affecting the nation’s forests.

The “most obvious” impact is an increased threat from wildfires, Stephenson said, as climate change creates conditions that make the blazes more frequent and intense—as seen in the record breaking fires in the summer and fall of 2020.

Fires can destroy the groves where giant sequoias grow and damage and even kill fully grown sequoias, some of which have been alive for thousands of years, Stephenson said. “In the last 10 years, 30 percent of the natural grove area for giant sequoias burned in wildfires,” he said. “That’s more than in the entire preceding century.”

That fact is particularly notable considering just how tough giant sequoias are, Stephenson said—not just in terms of being resilient to fire, but in resisting all harmful conditions to forests such as disease, parasites and drought.

In fact, during a particularly bad California drought from 2012 to 2016, hundreds of giant sequoia died due to a variety of factors, including disease, foliage loss and damage due to bark beetles—parasitic insects that feed on the wood of trees. But the loss of sequoia was minimal when compared to the overall damage California forests faced in that drought. More than 100 million trees died during that time, Stephenson said, a testament to the strength of sequoias.

“Lots of pines died, lots of firs died. Even the hardy infant cedar was dying,” he said. “The tree that died the least was giant sequoia, so there is good news there. They are really tough.”

Still, if global warming continues on its current path, Stephenson said, it’s possible that even the mighty sequoia could see significant damage to its populations in California and around the world. How humans move forward with conservation efforts and how successful they are in reducing greenhouse gas emissions over the coming decades could determine where sequoia can grow and in what quantity, he said.

If anything, Stephenson said, seeing the kind of stress sequoias face today should warn us that climate change has already pushed many tree species to their limits. “Sequoias really may not be the canary in the coal mine because they are so much more resilient than the surrounding tree species,” he said. “It’s almost like the sequoias are finally starting to feel the effects.” 

—Kristoffer Tigue

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