The Windy Fire burns in Sequoia National Forest in September 2021.

The Windy Fire burns in Sequoia National Forest in September 2021. Noah Berger / AP Photo

Can ‘Immortal’ Sequoias Survive the Ravages of Climate Change?

California’s giant sequoias, some more than 1,000 years old, are facing an existential threat from increasingly intense wildfires linked to warming and drought. An urgent federal push to thin forests in an effort to save the big trees is drawing criticism from conservationists.

In 2015 a lightning strike started what became known as the Rough Fire, which eventually burned more than 150,000 acres of forest east of Fresno and just west of Kings Canyon National Park.

The blaze burned into seven different sequoia groves in Sequoia National Forest, as well as a grove called the General Grant Complex in Kings Canyon National Park. As the flames died down and the smoke cleared, experts realized that an unusually large number of big sequoias had been killed by the blaze — 27 on park land and 74 on national forest.

The deaths of so many sequoias in one year was unheard of, and it deeply alarmed people who research and care for redwoods, some of whom wept at the sight of dead giants that had stood for more than a thousand years. After the Rough Fire, said Ben Blom, director of stewardship and restoration for the Save the Redwoods League, the idea of immortal sequoias no longer seemed to be true.

While the impacts of the Rough Fire were worrisome, it wasn’t until 2020 and 2021 that “things changed [by] orders of magnitude,” said Blom. “We’re talking tens of thousands of big trees dying in those two fire seasons.” It was after those fires, Blom added, that “we realized the big trees were facing an existential crisis.”

The crisis is rooted in climate change — which has caused record heat and drought, more insect pressure, and more high-intensity fires in California — combined with a century-long history of suppressing frequent, low-intensity fire.

A firefighter at the base of a towering sequoia in Long Meadow Grove in Sequoia National Forest.

A firefighter at the base of a towering sequoia in Long Meadow Grove in Sequoia National Forest. Patrick T. Fallon / AFP via Getty Images

In response to the emergency, experts declared a code red and are now working quickly to try to save the giants that remain. Teams of biologists, Native American tribes, and government agencies are urgently thinning the overgrown woodlands that surround the big trees and conducting prescribed burns. Research shows that such efforts help prevent extremely hot fires that can reach the sequoia canopy.

But such “active management” — which includes logging with heavy equipment and chainsaws in protected and unique ecosystems — has also sparked controversy. A bipartisan Congressional bill to further fund thinning efforts is being challenged by a coalition of conservation organizations who contend the legislation does not provide for adequate environmental review.


Giant sequoias are, by volume, the largest trees in the world, indigenous only to California. Reaching heights of 300 feet, they occur in 80 groves or grove complexes along the western flank of the Sierra Nevada mountains in Central California. All but eight of those groves occur in a narrow, 60-mile-long band at elevations between 4,000 and 8,000 feet. Coast redwoods, which are related to giant sequoias, are generally taller — reaching up to 350 feet — though not as big around.

For a long time, sequoias were thought to be indestructible. With their thick, flame-resistant bark and elevated crowns they are well adapted to wildfire. When a fire comes through, they aren’t usually killed. In fact, they thrive as their competitors for light, water, and nutrients are removed, and the fire’s heat opens the sequoia’s cones, facilitating the release of seeds for reproduction. Insects don’t kill them, nor does disease. That is why many of these trees live for thousands of years: The oldest sequoia is more than 3,200 years old. In North America, only bristlecone pines grow longer.

The General Sherman Tree in Sequoia National Park. It is the largest living tree, by volume, on earth.

The General Sherman Tree in Sequoia National Park. It is the largest living tree, by volume, on earth. Ovidiu Hrubaru / Alamy Stock Photo

Sequoias have become vulnerable to fire primarily due to drought. From 2012 through 2016, California experienced the most severe drought since instrumental climate records have been kept. The last two years of rain and snow officially ended the drought, but the state’s climate continues to warm — average summer temperatures have increased 3 degrees F (1.8 degrees C) since the end of the 19th century. As the temperature increases in a linear way, vapor pressure deficit — essentially, the thirstiness of the atmosphere — increases exponentially, pulling an increasing amount of water from trees, other plants, and soil.

As the drought continued, native bark beetles swooped in and began killing large tracts of California’s conifer forests, though not the sequoias. Vast tracts of white fir, red fir, and especially ponderosa pines — an estimated 147 million trees — died beneath the sequoias, their needles brown and tinder dry. And then the fires came.

“You got a sea of brown trees killed by beetles and drought, with the monarchs [trees at least 4 feet in diameter and often much bigger] interspersed among them,” said Blom. “The way fires kill giant sequoias is by ladder fuels that can get the fire up into the canopy. It was a perfect storm of conditions that allowed this all to happen.”

Another factor contributing to the forest’s vulnerability was the removal, during the settlement period, of Indigenous people from most of the American landscape, which ended their use of so-called good fire — frequent low-intensity blazes that increased forage for game animals. “All tribes throughout California have always done cultural burning, and it’s a practice we continue to use,” said Kenneth McDarment, a council member for the Tule River Indian Tribe. “It’s a good thing for the forest.”

A burned area of Kings National Park in November 2021.

A burned area of Kings National Park in November 2021. Daniel Jeffcoach / National Park Service via AP

Historical research shows that low- to moderate-intensity wildfire — sparked by either lightning or Indigenous peoples — occurred at six- to 35-year intervals, greatly reducing fuel loads. But that regime changed in the early 20th century. Responding to a series of large-scale wildfires on public lands, federal agencies in 1935 adopted the so-called “10:00 a.m. policy,” which decreed that all fires be extinguished by ten o’clock on the morning after they were spotted. As fire science and forest ecology evolved, federal agencies took a more nuanced stance, allowing natural-caused fires to burn in some areas. Meanwhiles, fuels were building up.

“When I look at the National Park Service groves, we see over 50 suppressed lightning-caused fires that could have [beneficially] burned into these groves in the last 80 to 100 years,” said Christy Brigham, chief of Resources Management and Science at Sequoia and Kings Canyon National Parks. “And it’s true across the range.”

The 2020 and 2021 fire seasons were a wake-up call: flames had killed between 13 and 19 percent of all giant sequoias more than 4 feet in diameter, and many trees were far larger. Before fire killed the King Arthur tree in Sequoia National Park, it was the eighth largest giant redwood in the world.

In 2022 officials who oversee groves in national forests and national parks declared an emergency and initiated large-scale mechanical and hand thinning of the sequoia forest, followed by the burning of the slash and prescribed burning. Removing this material has an added benefit — making more precipitation available to the trees that remain, increasing their resilience.

Locations of six recent wildfires that impacted giant sequoias. Sequoia groves are shaded in dark red.

Locations of six recent wildfires that impacted giant sequoias. Sequoia groves are shaded in dark red. National Park Service / Adapted by Yale Environment 360

A recent review of the literature on the value of thinning and burning to mitigate wildfire hazard, published in Ecological Applications, found that “a range of proactive management actions” — including managed wildfire, prescribed burning and mechanical thinning — “are justified and necessary to keep pace with changing climatic and wildfire regimes.” The paper acknowledged these actions weren’t necessarily appropriate in all kinds of forest, and it warned that if thinning is poorly executed it can exacerbate wildfire damage.

According to Blom, whose group favors thinning dense stands of young trees and reducing accumulations of vegetation and woody debris from the forest floor through prescribed burns or mechanical methods, there are about 26,000 acres of land to be cleared in all 80 sequoia groves on federal land, with some 8,000 acres already treated.

On their reservation, the Tule River Indian Tribe has been managing eight sequoia groves for 40 years. McDarment believes those efforts limited tree damage when the recent wildfires swept through. The tribe is planning to reintroduce beavers next spring; their dams will help keep more water in the meadows near the groves.

Meanwhile, foresters are studying the best way to add trees to already burned areas. Researchers have established seedling plots to study which genomes, from sequoias as well as other conifers, will survive the best in anticipated future conditions. “We’ll check those over time and see which ones grow well,” said Joanna Nelson, director of science and conservation planning at the Save the Redwoods League.

Firefighters clear dry vegetation in Sequoia National Forest to help keep fires at bay.

Firefighters clear dry vegetation in Sequoia National Forest to help keep fires at bay. Mario Tama / Getty Images

Earlier this year, U.S. lawmakers introduced a bipartisan bill called Save Our Sequoias that would provide additional funding for sequoia thinning. The bill received support from forest products, ranch, farm, and recreation groups. But a coalition of 80 environmental groups opposed the bill, in a letter to members of Congress, saying it would set a nationwide precedent that allowed federal agencies, under the guise of an “emergency,” to waive the environmental reviews required by the National Environmental Policy Act, the Endangered Species Act, and other environmental laws.

Without those reviews, and community and scientific input, the group said, the bill would “lead to rushed and poorly planned projects with major impacts on soil, streams, and wildlife that would result in increased wildfire risk.” No hearings have been held: the bill remains in limbo as the Forest Service and National Park Service continue to thin.

But not without pushback. In 2022, the Earth Island Institute sued the National Park Service to stop thinning activities in Yosemite National Park, claiming the agency had short-circuited environmental review and was logging illegally. The park halted its projects until a federal appeals court ruled in September that these activities were legal. Later that month, Wilderness Watch, the Tule River Conservancy, and the Sequoia ForestKeeper filed suit against mechanized logging in Sequoia and Kings Canyon National Parks, claiming it violated the Wilderness Act.

The debate is sure to intensify as the Biden Administration has committed $50 billion over 10 years to reduce fuel loads on 50 million acres in 11 Western states.

But advocates say action is urgently needed. “These forests we care deeply about could be converted to shrubland with repeated high-severity fires of the kind we are seeing,” said Nelson, of the Save the Redwoods League, citing a recent study that evaluated dry conifer forests of the western United States. “We know what we need to do in responding to climate disruption, and we need to do everything we know how to do. We need limits on greenhouse gas emissions, and we also need active management to have giant sequoias around.”