Wildfires are killing California's ancient giants. Can seedlings save the species?

On a late autumn day, a team of forestry workers spreads out among the burned trunks of giant sequoia trees. The 1,000-year-old trees in the grove are dead but still standing, killed in an extreme wildfire that raced through Sequoia and Kings Canyon National Parks.

In the shadow of one of the trees, the crew gets to work, pulling tiny, 4-inch seedlings out of bags clipped to their belts and tucking them into the dirt.

"Wish it some luck and that's it," says Micah Craig of the Eastern Sierra Conservation Corps, standing back to look at the young sequoia. He then grabs another seedling, part of a historic planting effort that the National Park Service hopes will be enough to preserve one of the world's most iconic species.

Over only two years, about one-fifth of all giant sequoias have been killed in extreme wildfires in California. The numbers shocked ecologists, since the enormous trees can live more than 2,000 years and have evolved to live with frequent, low-intensity fires in the Sierra Nevada.

Recent fires have burned bigger and more intensely than sequoias are accustomed to, a result of the way humans have changed the forest. After the 2020 and 2021 fires, scientists watched the sequoia groves to see if the next generation of trees is emerging to replace their lost parents. In some places, seedlings are filling the forest floor. In others, fewer are emerging from the burned soil.

The smaller numbers of seedlings concerned scientists and the National Park Service. So in a historic step, the agency for the first time has begun replanting some severely burned areas. With a life span of thousands of years, the new seedlings will grow up in a climate that's rapidly changing. So, park officials are bringing in seedlings from other sequoia groves, ones that may have the genetic tools to handle a more hostile future.

The project has run into opposition. A handful of conservation groups are suing to halt the effort, arguing that such intervention shouldn't occur in an area designated as federal wilderness and that the sequoia trees could possibly regenerate adequately on their own.

The debate is one occurring on public lands across the country as the impacts of climate change get worse. Land managers face a key question: As humans take an increasing toll on natural landscapes, how far should we go to fix it?

A carpet of green

Hopeful signs have emerged in the wake of the KNP Complex Fire, which tore through Sequoia National Park in 2021. The forest floor is still scorched black, but in some areas, thousands of lime-green sequoia seedlings have sprung up, a few inches high.

"It's awesome," says Christy Brigham, chief of resources management and science at Sequoia and Kings Canyon National Parks. "This is what has happened for millennia."

The lifecycle of sequoias is bound to fire. The massive trees, often 15 feet around, are protected from the heat by a thick, shaggy bark. Their lowest branches are far from the forest floor, reducing the chances they'll ignite when smaller trees burn. And when a fire's heat rises, the sequoias' cones open up, releasing thousands of seeds. Those seeds sprout quickly in the newly cleared soil below their parent trees. Most of the seedlings will die, eventually leaving only one or two giant trees centuries from now.

"Lots of bad things are going to happen to these," Brigham says, looking down at the carpet of green. "Another fire, fire after fire, before they get that big. Dead trees are going to fall on them. So they make a lot. A lot, a lot, a lot."

High above, the thousand-year-old sequoias in this part of Redwood Mountain Grove are still alive, their broccoli-shaped tops still green. The fire burned at low or moderate intensity here because the forest floor was relatively clear of brush and other vegetation that could burn. National Park Service crews had previously done prescribed burns, purposely using fire to remove the dry, dead fuels.

Gates of Mordor

Farther down the trail, it's a different story. Many of the giant sequoias have little or no green foliage left, their bare, jagged branches rising high above the rest of the forest.

"We have now arrived at the location we call the Gates of Mordor," Brigham says. "These trees are not coming back."

The KNP Complex Fire roared up this sequoia grove in less than a day. Fire crews made a last-ditch effort to save some of the enormous trees, clearing the vegetation around them as the flames moved in.

"It was horrible," Brigham says. "I don't think I've cried so much in my entire life."

The forest here was primed to burn. Historically, the Sierra Nevada saw regular low-grade wildfires, caused by lightning strikes and set by Native American tribes who shaped the landscape through controlled burning. But for the last century, humans have extinguished wildfires, allowing dead and dry vegetation to build up on the forest floor.

Extreme drought, exacerbated by climate change, has also led to millions of smaller trees dying in recent years. Water-stressed pines and other trees were more vulnerable to attacks from bark beetles. Researchers found that the dead trees acted as kindling, contributing to the extreme heat and intensity of the KNP Complex Fire.

Along with two other extreme fires in 2020-21, between 13% and 19% of all giant sequoias were killed, up to more than 14,000 trees.

"We have never seen anything like this in giant sequoia," Brigham says. "Large giant sequoias, before now, survived wildfire."

With so many giant trees gone, teams from several federal agencies turned to another key issue: the next generation of sequoias. They surveyed how many seedlings are growing below the burned trees. Two studies from scientists at the U.S. Geological Survey found that some of the severely burned areas have lower densities of sequoia seedlings, compared to the numbers found after previous fires.

Brigham says it's possible that too many sequoia cones and their seeds burned up in the fire. But with fewer adult trees left alive to make seeds in the future, there's a risk some of this sequoia grove won't come back.

"These parks were in part established to conserve sequoias," Brigham says. "What would it mean for that mission if we did nothing here?"

A replanting effort begins

In the late afternoon, a line of mules winds its way through the burned sequoia grove. On their backs, they carry boxes of sequoia seedlings deep into the backcountry. A crew from the Eastern Sierra Conservation Corps takes the seedlings on the last steps of their journey, searching for planting spots that offer some protection from the upcoming summer heat.

"Planting sequoias, that's a legacy thing. Something we were all stoked to do that will transcend after us," says crew member Micah Craig.

Most of these sequoia seedlings were grown from seeds collected from this same grove. But 20% come from seeds collected from other groves. Sequoia seedlings are vulnerable to heat and drought, conditions that will get more extreme as the climate keeps changing. With that in mind, managers selected seeds from groves at lower elevations that already naturally live in hotter conditions. The idea is to increase the genetic diversity, in case those trees are better adapted to a hotter, drier future.

"We have the ability to give this grove a little bit of a bigger toolkit for adapting to changing conditions, and that's what we're trying to do," Brigham says. "We're asking a lot of these trees to survive for 400 years, 1,000 years, and they can do it, but let's give them a little help."

The technique, known as "assisted gene flow," has been used in a handful of cases already to help coral survive a hotter climate or whitebark pine trees resist disease. It's part of a larger toolkit land managers are beginning to consider as ecosystems struggle to keep up with climate change. The National Park Service has developed a new framework for considering when to intervene, known as "resist, accept, or direct," acknowledging that some ecosystems will need help to resist changes, while in others, change may be inevitable.

Lawsuit filed to stop replanting

A group of four conservation groups is suing to halt the project, contending that because the sequoia groves are protected under the federal Wilderness Act, a higher level of intervention isn't appropriate. They argue that having wilderness protection means the land should remain untouched, even if that means losing sequoias there.

"We need to allow nature some places where human beings aren't trying to be the managers, aren't trying to be the gardeners," says George Nickas, executive director of Wilderness Watch, one of the groups that filed suit. "Because we're the ones that messed it up, it doesn't flow that we're the ones to fix it. That's that sort of arrogance of humanism, if you will. That's when we need to learn to step back."

The Wilderness Act specifies that protected areas should be "untrammeled by man." That framing has frustrated Native American tribes in California, which shaped the landscape for millennia with cultural, or prescribed, burning.

The National Park Service doesn't comment on pending lawsuits. But in public documents, it responded that language in the Wilderness Act mandates that the land be "protected and managed so as to preserve its natural conditions," and the act doesn't infringe on the agency's responsibility to preserve the ecosystem.

The conservation groups' lawsuit also contends that sequoias in severely burned areas could regenerate on their own. Sequoia seedlings tend to do best in places that have burned more intensely, since it clears out vegetation that shades the forest floor.

"I'm not worried about it because the system is massively and redundantly resilient to these sorts of disturbances," says Chad Hanson, director of the John Muir Project, another group that joined the lawsuit.

Hanson contends that any number of sequoia seedlings, no matter how low, is adequate for the groves to endure into the future. However, numerous scientific studies show that sequoia seedlings have high rates of mortality over the first few centuries of life, with more than 90% dying in the first 20 years alone.

In proposing the project, the National Park Service says climate change poses an even greater risk that sequoia seedlings will struggle to get established. Hanson says he'd prefer that the park service monitor the seedlings' survival before making a decision to replant.

"What I would say is if they start dying at high levels, which is inconsistent with the data we've had up until this point, then I would have to evaluate my assumptions and maybe would need to do something there," Hanson says.

The debate is a sign of the increasingly complex decisions land managers are facing in a hotter climate. In the face of unprecedented impacts, the risk of losing species only gets worse. Managers are having to weigh bigger and bigger human interventions, if they're seeking to preserve what's left.

Brigham says that as one of the largest and longest-living species on the planet, giant sequoia trees are forcing that conversation to happen.

"You cannot look at them without thinking about 1,000 years in the future," Brigham says. "They demand better of us. And I think we need that. We need those species that are being impacted by climate change that we love to be, like, hey, I think you can do better."