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They’re Among the World’s Oldest Living Things. The Climate Crisis Is Killing Them.

Sequoia Crest, Calif. — Until a few years ago, about the only thing that killed an old-growth giant sequoia was old age.

Not only are they the biggest of the world’s trees, by volume — the General Sherman Tree, considered the largest, is 36 feet in diameter at its base and 275 feet tall — they are among the oldest. At least one fallen giant sequoia was estimated to have been more than 3,200 years old.

They last so long that, historically, only one or two of every thousand old-growth trees dies annually, according to Nate Stephenson, a research ecologist for the United States Geological Survey.

Fire always was a frequent visitor to sequoia groves, but rarely a threat. Mature sequoias are virtually fireproof because the bark can be several feet thick. The crowns, the top where branches and needles are, are so high that they stayed above the fray of fire, out of harm’s way.

Until now.

Dr. Stephenson was home in Three Rivers, Calif., this summer as the Castle Fire raged in the nearby mountains. Ash and debris fell from the sky, big enough to be identified.

“I could go, ‘Oh, there’s a fir needle, that’s incense cedar, that’s oak, that’s a pine,’” Dr. Stephenson said. “Then I saw a piece of giant sequoia ash, and that really drove it home. I thought, ‘Oh, no, I bet some of those sequoias, their crowns are burning.’”






Giant sequoia groves

CALIFORNIA

Extent of fire

Intense fires engulfed the giant sequoia groves, killing trees.

More intense burning

Unburned grove

Burned grove

S.Q.F. Lightning Complex fires

In the Alder Creek grove, hundreds of the oldest trees are thought to have died.

SPRINGVILLE

Giant sequoia groves

In all, thousands of trees died in groves damaged by fire.

Area of

detail

Giant sequoia groves

CALIFORNIA

Extent of fire

Intense fires engulfed the giant sequoia groves, killing trees.

More intense burning

Unburned grove

Burned grove

S.Q.F. Lightning Complex fires

In the Alder Creek grove, hundreds of the oldest

trees most likely died.

Giant sequoia groves

In all, thousands of trees died in groves damaged by fire.

Area of

detail

Giant sequoia groves

CALIFORNIA

Extent of fire

Intense fires engulfed the giant sequoia groves, killing trees.

More intense burning

Unburned grove

Burned grove

S.Q.F. Lightning Complex fires

In the Alder Creek grove, hundreds of the oldest trees most likely died.

Giant sequoia groves

In all, thousands of trees died in groves damaged by fire.

Area of

detail

Intense fires engulfed the giant sequoia groves, killing trees.

Giant sequoia groves

CALIFORNIA

Fire intensity

Extent of fire

Burned grove

S.Q.F. Lightning Complex fires

In the Alder Creek grove, hundreds of the oldest trees most likely died.

Unburned grove

Intense fires engulfed the giant sequoia groves, killing trees.

Giant sequoia groves

CALIFORNIA

Fire intensity

Fire extent

Burned grove

S.Q.F. Lightning Complex fires

In the Alder Creek grove, hundreds of the oldest trees most likely died.

Unburned grove


Since 2015, nearly two-thirds of the roughly 48,000 acres of giant sequoia groves have burned — about half of that since August. The amount of groves burned in the past five years is double what had burned in the previous century.

But it is not just the number of fires or acres they consume. Fires are burning bigger, hotter and higher than ever. A historic drought from 2012 to 2016 and huge infestations of bark beetles killed millions of trees in the mixed-conifer forests of the Sierra Nevada, leaving them behind as kindling.

Within those dying forests are the remaining giant sequoias, in roughly 70 groves speckled in the California mountains, rooted in the fray. Today’s fires are so big, so hot, that they can create their own weather systems, whipping up fire-spreading winds and creating columns of heat and smoke tens of thousands of feet high.

“The apocalyptic chickens are coming home to roost, way sooner than we thought,” said Christy Brigham, the resource manager at Sequoia and Kings Canyon National Parks, home to dozens of the remaining sequoia groves and the many of the biggest trees in the world. “We are seeing impacts now that we thought we would see in 50 years.”



The Stagg Tree, considered the fifth-largest tree in the world, was saved this year, perhaps by sprinklers.

In some ways, sequoias depend on fire. Their egg-sized cones are glued shut by resin, and extreme heat from fire dries them out and spreads seeds, like flakes of oatmeal, across the forest floor.

In the centuries before California was settled, scientists believe, about 4 million acres burned in a typical year, mostly in tiny freckles across the landscape — including in sequoia groves. They were a combination of natural fires that generally burned themselves out and prescribed fires managed by indigenous people.

Researchers studying a 1,400-year history etched into the rings of tree cores found evidence of fires at least every 30 years among sequoias. The forensic evidence stops about 100 years ago, as fire became seen as a threat to be suppressed, not part of a cycle to be managed. The forests thickened.

There is consensus among scientists that California must, in part, burn its way out of the current predicament with more prescribed fires — controlled, low-level burns designed to prevent catastrophic blazes later. But setting fires intentionally is a sticky undertaking, given all the jurisdictions and the landscapes crowded with people.

“We probably are never going to get back to 4 million acres of healthy, wonderful fire each year,” Dr. Shive said. “But we need to pick priority areas.”



Bark beetles have killed millions of trees in the West. Now they are being found in giant sequoias, an ominous sign.

Prescribed burns are easiest, though not easy, in remote locations like national parks. Sequoia National Park, the nation’s second-oldest, has been doing them since 1968, longer than any national park in the West.

The program was long considered a model of forest maintenance, at least before this year’s fires devoured parts of the national park. Now, the few hundred acres of prescribed burns in a typical year have proved little match for today’s megafires.

“Now, I’m like, ‘Dude, that is not good enough — we need to rethink this whole thing,’” Dr. Brigham said. “If we can have 16,000 acres of sequoias burn up in a wildfire in a single year, we cannot go 200 acres at a time. It’ll be all burned up in uncontrolled wildfire before we’re done.”

On a late-October afternoon, Dr. Stephenson toured a grove that included the General Grant Tree, the world’s third-largest. A wildfire swept through a portion of the grove in 2015, after park officials had prescribed a burn to one side of a hiking trail.



Nate Stephenson, a research ecologist, in Grant Grove.

That trail now serves as a stark dividing line. On the side that had been recently burned, just one of the 111 old-growth sequoias was killed. On the other side, about 30 percent of the large sequoias were dead, along with most other big conifers.

“Prescribed fire is so good at reducing damage when wildfires come,” Dr. Stephenson said.

Dr. Stephenson said that giant sequoias can suffer 90 percent “crown scorch” — extreme heat that does not consume the needles, but turns them brown and lifeless — and still survive. What is killing the trees now, he and others said, are flames that reach the crown at the top — torching the crowns, like a giant matchstick.

Damage is mounting.

In 2017, fire swept through the Black Mountain Grove in Sequoia National Forest, killing nearly a third of the 183 old-growth sequoias that were surveyed. About the same time, a nearby blaze killed almost half the 104 mature sequoias in the Nelder Grove.

The starkest example in 2020 might be in Alder Creek Grove, one of 19 groves to burn this year. It is home to 483 ancient sequoias with a trunk diameter of six feet or more, among them the Stagg Tree, thought to be the fifth-largest in the world.

Alder Creek had been the last major stand of sequoias in private hands. The Save the Redwoods League, founded in 1918 to protect redwood forests (and, increasingly, sequoias) bought the 530-acre grove for $15.7 million just last year.



Giant sequoias share the forest with other large conifers, often dwarfing them, and historically stayed above the fray of most fires. That has changed.

Dr. Shive, the league’s chief scientist, spent much of this year surveying the rugged property and pondering the grove’s long-term health.

In September, the Castle Fire crept nearby, paused on a ridge, and swept through in a matter of hours.

In October, Dr. Shive wandered through blackened parcels, counting dead old-growth sequoias. There were at least 80, and some areas had not yet been surveyed. Across the range of giant sequoias, this year’s death toll could be in the thousands.

The Stagg Tree survived, perhaps in part because firefighters had hastily run hoses and turned on sprinklers at its base. But it will take more than sprinklers to fight off the likely destruction to come to the giant sequoias.

“They are literally irreplaceable,” Dr. Shive said. “Unless you have 2,000 years to wait.”