When ash began landing in Nate Stephenson’s yard 30 miles west of a fire burning in Sequoia National Park this summer, he knew the trees he’s studied for four decades were in trouble.
“I started to see some giant sequoia ash falling and that's when I knew it was going to be really bad,” the USGS research ecologist said about his home in the mountain community of Three Rivers.
Multiple lightning-caused fires this summer in and around Sequoia National Park merged into the SQF Complex. Months later the blaze is still burning and is about 90% contained at just over 174,000 acres.
The giant trees, which thousands of people visit yearly, were stressed by a multi-year drought. Wildfires this year killed hundreds of the largest trees. The extent of the damage to the groves from wildfires is unknown, but from helicopter flyovers scientists say the damage is unfathomable.
“The trees just got wiped out in a way that is unprecedented ... it's like watching elephants go extinct,” said Christy Brigham, science chief of Sequoia and Kings Canyon National Parks.
It could be a precursor of what’s to come for the big trees. Those same scientists say a new threat is emerging — bark beetles that feast on the bark of stressed out giant sequoias. Unless scientists come up with ways to prevent these insects from harming giant sequoias their fate could be like the millions of trees that died from another beetle during the last major drought.
“We have very strong preliminary evidence that these trees were weakened… by drought and by fire damage, but they were ultimately killed by a full on attack from this native bark beetle,” Brigham said.
The SQF Complex wasn’t the largest this year in the state by any measure — the August Fire in the coastal range burned well over a million acres — but for the iconic trees it was devastating, says Brigham.
Experts say that climate change stressed the trees out as well as a history of fire suppression in the Sierra Nevada, which has overloaded forests with fuels. Both mixed with windy conditions cause fires to burn fast and hot.
Giant Sequoias only naturally grow on the western slope of the Sierra Nevada and there are fewer than 50,000 left in the wild.
“If you got all giant sequoia groves and put them together, it's an area smaller than Sacramento,” Stephenson said.
The Stagg Tree is the fifth largest known tree in the world.Photo by Max Forster, Save the Redwoods League
Even with all those threats Stephenson said he doesn’t believe the extra large trees will go extinct, although they almost did once before about 4,000 years ago. But he says those towering 2,000 year-old trees that people draw inspiration from are at risk of burning up.
“Those are just limited to this handful of giant sequoia groves scattered along the western slope of the Sierra Nevada,” he said. “Those are the groves that we think might be threatened if temperatures keep rising.”
At Least 1,000 Burned
Out of the more than 170,000 acres the SQF Complex burned, 16,000 acres are in the band of the Sierra Nevada where the enormous trees grow, said Kristen Shive, science director for the Save the Redwoods League.
On a plot of 65 acres of private land, Alder Creek, the fire burned 80 big trees. Shive says if what happened on the league’s land took place across the burn scar then she thinks the loss will “be tremendous.” Much of the grove didn’t burn hot and will do some good, Shive says.
Shive is paying attention to how severe the fire burned across the region where she says about 40% of giant sequoias were severely charred.
“You scale that up to almost 6,000 acres burned at high severity, that is going to be very huge losses, definitely hundreds,” she said. “I will not at all be surprised if it exceeds 1,000.”
Giant sequoia in the Alder Creek Sequoia Grove.Photo by Max Forster, Save the Redwoods League
This wasn’t the first time fires killed the big trees in recent history. In 2017, fires west of Yosemite National Park killed around a third of giant sequoia groves.
“We just didn't think that quite could happen and so it made us realize that we are really in a crisis situation with the amount of fuels,” she said. “Fast forward to 2020 and I am kind of blown away at the extent of high-severity fire.”
After looking at aerial imagery, Sequoia National Park’s fire ecologist Tony Caprio says more than 300 of these giants were incinerated in 12 groves in the parks and around a third of the entire giant sequoia range has burned this year alone.
“It's very, very preliminary, we haven't been out there on the ground,” he said. “There probably hasn't been that many large sequoias die in this short of time since the area was logged.”
This map shows the fire severity this year within the SQF Complex, which encompasses a number of giant sequoia groves.Save the Redwoods
These enormous trees are not mapped very well. While on private and National Park land there are estimates about how many trees perished, there's not much data in Sequoia National Forest and the Giant Sequoia National Monument because many of the groves are remote and there’s a lack of funding and resources to map them. That’s where scientists believe most of the damage has taken place.
“It would be wonderful if we had maps of the groves and of all the individual trees so we could just check them out using satellite imagery now, but we don't have those,” said Amarina Wuenschel, an ecologist for the Sierra, Sequoia and Inyo National Forests.
While Wuenschel's worried about how severe the fire burned the historic trees, she said fire in and around the groves isn’t all bad news. The hearty trees need fire to unlock seeds in their two-inch cones, so less severe burns could actually benefit the groves.
“Typically, they do pretty well after a high-severity fire and there's a pretty big flush of seedlings,” she said. “Most of those tend to not make it depending on the climate when the seedlings are young, but usually a fair amount do. But it will be interesting to see what happens when we have such large portions of areas that burn.”
Meet The Beetles
During the last multi-year drought four years ago, bark beetles sucked the life out of more than 129 million thirsty pine trees. At that time beetles weren’t harming giant sequoias, but now a different bark beetle is threatening the trees.
“Finally during this drought a small handful of sequoias got stressed enough that it looked like the bark beetle could take advantage of their weakness,” he said.
The beetle is native to the area and some think it's a cedar bark beetle, but the exact species is currently uncertain, says Stephenson with USGS.
So far 32 trees have been killed by the beetles, and scientists are banding together to investigate the correlations between the red trees and the bugs.
Black Mountain Grove, which is part of the Giant Sequoia National Monument, burned in the 2017 Pier Fire. Save the Redwoods League counted at least 50 dead monarch trees (sequoia greater than three feet in diameter) within the grove.Courtesy of Save the Redwoods League
“The little beetles in giant sequoias weren't even on the managers' radar screens,” Stephenson said of the different agencies that manage land with giant sequoias on them.
He says if the climate crisis continues he’s fearful giant sequoias could continue to succumb to the beetles.
“The main thing I'm working on right now is trying to understand its life cycle and if there are ways to control it, and to be sure that we don't accidentally make trees more vulnerable to it,” he said.
But one surprise Stephenson noticed is that the trees that were most vulnerable were growing in the wettest areas. That was a big surprise, because the bark beetles that killed pines attacked trees that were lacking water.
“We're developing hypotheses on why that might be,” he said. “It's another one of these curveballs that nature throws at you.”
Swift Action Is The Solution
With around a third of all of the wild giant sequoia range burned in 2020 alone, scientists say two things need to happen to prevent more loss of the big trees: continued action on climate change to prevent temperatures from warming and work to prepare these big trees for the future.
Stephenson with USGS says this includes prescribed fire in giant sequoia groves and physically thinning forests.
“At the very top of my list is to better protect the groves,” he said. “Let's do some more prescribed burning in those groves and near those groves to protect them from wildfires.”
Sequoia and Kings Canyon National Parks have experimented with prescribed fires often and Brigham says it works. She says an area called Grants Grove had been treated multiple times with prescribed burns and when a wildfire came through in 2015 the fire slowed down.
“The fire behaved very differently, it laid down, it became a surface fire and the sequoias survived very well,” she said.
With the knowledge that thinning and prescribed burns are the immediate answer to protecting the trees, Shive, with Save the Redwoods League, says every entity involved should focus on the largest areas of sequoias and the groves in the best condition.
“We're in a crisis in the giant sequoia range, and we just need to get out there,” she said. “This is a warning bell and we need to go to the green forest that hasn't had treatment yet and do what we can.”
Shive said the main hurdles are funding the projects and training enough people to do prescribed burns. Legislators would like to fix it by ramping up burns, creating training programs and even a new conservation corps with a focus on thinning forests.
“This threat is real and it's big, and we are on the verge of continuing to lose a lot of the world's ancient giant sequoias if we don't act,” she said.
