Severe fire can be good for giant sequoias. The ‘hopeful’ new research – and a giant debate
Ecologist Chad Hanson felt hopeful as he stood within a large burn scar in Sierra National Forest on a recent fall day.
This landscape, charred four years earlier in the Railroad Fire, might look to most like more than 1,000 acres of destruction – dead tree trunks rising from brush. But there’s far more than just bushes growing here. There are thousands of young giant sequoias, hundreds per acre, sprouting like weeds in every direction.
This section of Nelder Grove, previously home to less than a few dozen mature giant sequoias, will be home to many, many times more because of high-intensity fire that burned this area in 2017, Hanson said.
What’s happening in Nelder Grove is unprecedented giant sequoia regeneration, in numbers and rate of growth, he said, because the fire burned at high severity. In another section of Nelder Grove, where the fire burned at low and moderate intensity, few young giant sequoia seedlings were seen growing last month.
Fire, even some severe fire, is known to be beneficial for giant sequoias. Flames are needed to open sequoia cones to disperse seeds within. But what’s happening in Nelder Grove is taking that understanding to another level. Not only is some fire good for their reproduction, the hottest fires are best for that – and not just in small patches, Hanson said. It’s a controversial new assertion.
Hanson doesn’t see anything controversial about it when he looks upon the extraordinary new growth in Nelder Grove, what he describes as the kind scientists have been “hoping and begging and dreaming of” for a species that has “been slowly dying off without any fanfare for the better part of a century.”
Giant sequoias can live over 3,000 years, but can grow large and to maturity within 150 years, said Hanson, co-founder and director of the John Muir Project, a nonprofit that acts as a watchdog in federally managed public forests.
“We’ve been loving these groves to death,” he said, “thinking that we’re saving them from fire, and that thing that we’ve been ‘saving’ them from, in quotes, is actually the thing that they need to survive.”
He describes the emerging science as “fundamentally positive and hopeful.”
“I think we could all use a little bit of that right now. Frankly, I’m sort of mystified by some of the resistance to scientific evidence that’s actually positive and hopeful.”
Hanson describes the high-intensity fire patch he’s studying in Nelder Grove as the largest of its kind among giant sequoia groves since at least the 1870s. There’s much to learn in this relatively new frontier for sequoia science.
How well beloved giant sequoias fare after recent wildfires is setting the stage for future forest management practices in California.
What knowledge scientists glean from Nelder Grove, located along a bumpy dirt road just south of Yosemite National Park, will be critical in the wake of high-profile wildfires that burned through many Southern Sierra giant sequoia groves over the past couple years. Those include the KNP Complex and Windy Fire in 2021, and the Castle Fire in 2020, which have only brought a new sense of urgency to the debate over forest management.
Giant sequoias only exist in over 70 groves that stretch along the western slopes of the Sierra in California, from Tahoe National Forest in the north to Giant Sequoia National Monument in the south.
How many giant sequoias died in KNP, Windy and Castle Fire?
Giant sequoia mortality for the KNP Complex and Windy Fire is estimated at thousands of dead and dying trees according to estimates released Friday. Christy Brigham, Sequoia and Kings Canyon National Parks’ chief of resources management and science, said there was a mix of fire severity across 4,320 acres of 16 giant sequoia groves that burned in the KNP Complex, and that a lot of those giant sequoia grove acres burned at low and moderate severity, where “mainly beneficial effects of fire” are expected.
“On the unfortunate side,” she continued during a community meeting last week, “we did have 14% of the groves that burned at high severity, and some of those in pretty large patches. ... We’ll have to do additional fieldwork to see if we will get sequoias back in those areas.”
Gretchen Fitzgerald, an ecosystem staff officer for Sequoia National Forest, which envelopes Giant Sequoia National Monument, said the Windy Fire burned through 11 giant sequoia groves managed by the Forest Service, and two on the Tule River Indian Reservation. Of those groves, Fitzgerald said the Windy Fire burned 24% of them severely, affecting 400 to 450 acres of giant sequoias.
“We believe that most of the giant sequoias on these acres are probably dead,” Fitzgerald said last week. “We do not have any specific numbers, but it is probably over 1,000.”
About the recent monarch deaths, Forest Service ecologist Amarina Wuenschel added, “I don’t think the trade-off of losing large sequoias is worth the pulse of regeneration if the objective is to maintain the longevity of the grove population.”
Earlier this summer, Brigham and her colleagues shared preliminary estimates that said thousands of mature giant sequoias died – a startling 10% to 14% of the world’s population – in the 2020 Castle Fire that hit Giant Sequoia National Monument, Sequoia National Park and other surrounding lands. About three months after those estimates were released, the KNP Complex and Windy Fire ignited and burned through more giant sequoia groves in the same region.
National Park Service leaders hope to reopen Giant Forest in Sequoia National Park in early December. It’s home to the popular General Sherman tree, the largest tree in the world, that was not harmed by the KNP Complex, which is now 75% contained.
The Castle Fire mortality estimates are based largely on rapid-assessment satellite images taken shortly after that fire. Brigham cautioned that the numbers need to be assessed with field surveys and a peer review, and said the KNP Complex and Windy Fire has delayed that research. Brigham said final Castle Fire mortality estimates aren’t expected until early next year, at the earliest.
Hanson points to a lack of fieldwork in his belief that federal agencies have largely overstated the number of giant sequoias killed. He thinks mortality estimates will be overblown again for the KNP Complex and Windy Fire, and that fire mortality estimates are also lumping in some giant sequoias that previously died in the drought.
Hanson said more giant sequoias also survived because of a phenomenon he refers to as “flushing,” where new buds can later emerge from giant sequoias that might initially appear dead. This is called “epicormic shoots” in other scientific studies that describe the same process. If some greenery remains at the top of a giant sequoia after a fire, then they can survive, Hanson said. He said he’s already seeing some flushing happening in recent burn scars.
Nate Stephenson, a forest ecologist and scientist emeritus with the U.S. Geological Survey, also said epicormic sprouts, “new buds,” can emerge along parts of the trunk where fire killed foliage, as long as all the foliage isn’t dead.
“Sequoias are remarkably resilient to fire ... they can survive even after fire kills 90% to 95% of their foliage,” Stephenson said.
Still, scientists with federal agencies in the Sierra Nevada have defended their initial Castle Fire mortality estimates, what Stephenson was also part of.
Hanson additionally voiced concerns about some firefighting practices. The dropping of a new thick gel on some giant sequoias, which lasts longer than traditional fire retardant, could block tree pores – how they breathe in carbon dioxide, and breathe out oxygen – and Hanson said wrapping some sequoia bases in metallic, protective blankets only kept heat around trunks, instead of allowing flames to pass by naturally, like a wave.
Brigham called the gel “therm gel,” and said it was only dropped on a small portion of Muir Grove. It has not been applied to trees in this way before, she said, so there’s “no knowledge” of whether it would block stomata – the tiny openings, or pores, in plants. She said the trees will continue to be monitored for any effects.
Brigham said some monarchs were wrapped with blankets to keep embers from getting into their trunks, not to prevent crown fires. The first branches on mature giant sequoias are far above the forest floor.
Who is ecologist scientist Chad Hanson of the John Muir Project?
Hanson has disagreed with many federal land managers – and vice versa – especially those in the Forest Service and researchers supported by Forest Service dollars. Hanson argues that they have a financial conflict of interest, since the Forest Service – created for the purpose of bringing more water and timber to the American people – remains in the logging business.
“Unfortunately, the Forest Service is opportunistically and cynically using climate change to try to justify logging policies that are damaging the forest and making climate change worse,” Hanson said.
He’s been among their most vocal and high-profile critics – both in the news and in the courts, where the John Muir Project has had some victories – but he’s far from alone. Hanson points to hundreds of fellow scientists and a long list of scientific studies that have raised similar concerns.
The John Muir Project that he leads also has the support of the Earth Island Institute. It operates as one of its many environmental projects. The institute is a Berkeley-based nonprofit environmental organization founded four decades ago by David Brower, the Sierra Club’s first executive director.
Hanson lives in the San Bernardino Mountains in Southern California and makes frequent trips to forests throughout the state. He graduated from the University of California, Davis with a doctorate in ecology, a branch of biology that deals with interactions between living things and their environment. His published scientific research includes forest and fire ecology, along with how wildlife use burned forests. His most recent book, released in May, is titled, “Smokescreen: Debunking Wildfire Myths to Save Our Forests and Our Climate.”
What can we learn from Nelder Grove in Sierra National Forest?
Hanson doesn’t want the majority of any wildfire to burn intensely. But he thinks it’s natural for some mature giant sequoias to die in mixed-intensity fire, which includes severe fire. He sees recent giant sequoia deaths leading to the continued growth of many more new ones, at levels beyond anything previously seen in people’s lifetimes.
“I love giant sequoias. I love the giant sequoia ecosystem. And I know it may be counterintuitive for some people to think of a large mixed-intensity fire as being something that’s good for giant sequoias. And it may be difficult to think of a larger high-intensity fire patch as being the salvation of giant sequoias as opposed to the doom of them, but that’s what the science is telling us.
“We can’t deny it. I mean, look at this. Look at this,” Hanson continued while standing beside dozens of young giant sequoias in a large, high-severity burn scar in Nelder Grove on Oct. 27. “You just don’t see this kind of giant sequoia reproduction.”
In some cases, the young giant sequoias are already a bit taller than Hanson, who stands at a little over 6 feet 4 inches. They are sprinkled among a vast carpet of ceanothus bushes, whose existence aren’t hindering their growth, but rather providing some protection, Hanson said.
The forest floor here is thick with giant sequoia cones, with new seedlings sprouting every year since the 2017 Railroad Fire, although no living mature giant sequoias are within sight. Hanson can easily identify how much the older saplings grow annually by looking at their slender trunks. They are a much more vibrant green starting from where this year’s new growth began.
Hanson said many times more giant sequoias grow back, and much faster, in a high-intensity fire patch than after low and moderate fire for three reasons:
- Flames were hot enough to burn off the “duff and litter,” an ecological term for the spongy bed of plant materials, like pine needles, that sit above soil, which can be quite thick in the forest.
- Burning off those materials enables seedling roots to reach a nutrient-rich bed of mineral ash below.
- There is more sunlight coming through the canopy because older trees died, and the extra light speeds growth.
Ecologists from various agencies and organizations, including the National Park Service and Forest Service, widely agree that mixed-intensity fire, which includes severe fire, is beneficial. But the messaging to the public about that is less clear.
When asked about research showing giant sequoias experience significant reproduction after moderate and high-intensity fire, Brigham responded, “This is true – but the key issue here is SCALE. Giant sequoia seedlings do best in SMALL canopy gaps.”
Brigham described it another way during a community meeting last week in Three Rivers: “Mixed conifer and giant sequoia is not adapted to high-severity fire, on a large scale.”
The thousands of thriving young giant sequoias in Nelder Grove are evidence otherwise to Hanson.
Wuenschel worries about their vulnerability.
“While sequoias are very fire-adapted, and I think they could survive a burn in the right conditions as early as ten to twenty years of age, the fuel conditions in the grove now are conducive for another high severity burn,” Wuenschel said, “and the second time, there would be no seed-release.”
Of all the mature giant sequoias in Nelder Grove, 38 of 92 monarchs died, she said.
Wuenschel isn’t planning to revisit the new growth in Nelder Grove until 2023, more than five years after the Railroad Fire, because 75% to 95% of seedlings die in their first 20 years of life, she said.
Many are no longer considered seedlings, however. They are more established saplings – young trees around breast height or above, with a better chance of survival. Hanson said other researchers aren’t doing as much fieldwork as he is in large, severe burn scars because “they already think they know the answer, or because it’s just too difficult.”
“What we’re finding is that all of our assumptions from the past are wrong,” he said. “These forests are regenerating vigorously.”
Brigham said initial observations about how well recovery happens after extreme fire may vary based on factors like distance from cone-bearing trees, erosion, drought, and how many cones were incinerated vs. scorched. She said a colleague who walked through parts of a 40-acre high-severity burn scar from the Castle Fire found less than 20 giant sequoia seedlings growing there in October.
Hanson’s findings in Nelder Grove haven’t received a warm reception from Forest Service officials, who noted how he hasn’t applied for a research permit there. They said the grove is closed to the public (along with many other forest destinations), and has been off and on since the Railroad Fire due to hazards from fire and winds. A district ranger said Hanson likely wouldn’t have been granted a permit had he applied for one, and that his walking through the grove could hurt sequoia roots.
Hanson said he hasn’t placed anything in Nelder Grove or altered it, and has only been recording observations for a new study that will be published soon. He was unaware of the Nelder Grove closure – as were several hikers in the grove on a recent fall day, where no closure signs were seen along quiet back roads and trails.
As for his footsteps, Hanson pointed out how the Forest Service allowed far heavier cattle to graze in Nelder Grove after the Railroad Fire. Cow poop in the grove last month showed evidence of that. The Forest Service didn’t confirm or deny it when asked about that this week.
Climate change and California forests
Until more recent years, most didn’t worry about wildfires posing much of a threat to fire-adapted giant sequoias. But as wildfires have grown larger and more intense, spurred by climate change exacerbated by the actions of people, there’s been a growing feeling that people also need to do more to fix things.
Hanson said many are using people’s fear of losing beloved giant sequoias to garner more support for harmful forest management practices.
Hanson said taking action in and around communities to protect people from wildfires is warranted, but thinks land managers should largely leave more remote areas alone. He thinks solutions like forest thinning are really euphemisms for logging that only create more wildfire danger, and pump more carbon into the atmosphere overall than wildfires do.
“What the current science is telling us is that the typical commercial thinning, logging, operation emits three times more carbon into the atmosphere than a wildfire alone,” said Hanson, referring to the whole process, including the burning of excess wood materials from logs that don’t become timber.
“It doesn’t make any sense from a climate change perspective,” he continued. “Of course, that’s making climate change worse, which is influencing fires more. And then they’re doing more post-fire logging and more commercial thinning, making climate change worse, and it’s an endless cycle.”
On a global level, forests across the planet got more love and attention earlier this month when world leaders pledged to end deforestation by 2030 during the United Nations’ COP26 summit that addressed climate change.
In California, giant sequoias have often been pictured in the fight to restore forest health. California Gov. Gavin Newsom signed a bill in September from Sequoia National Park as ash fell around him from the KNP Complex that promises $15 billion in aid to address climate change and wildfires.
What’s happening now? Logging, thinning, prescribed fire
After the Castle Fire, land managers said they wanted to do more vegetation management in giant sequoia groves.
Hanson said a number of politicians at the state and federal level are now talking about “doubling down on logging” in national forests “under different deceptive euphemisms like thinning and fuel reduction.”
Hanson is one of the authors of what he called the largest published scientific study that shows how forests with the most logging typically burn in the hottest fires. They analyzed three decades of data for more than 1,500 fires that burned 23 million acres. These fires can be devastating, including what happened in Paradise, where 86 people died from the Camp Fire that first raced through treated areas outside town, Hanson said.
Decades of fire suppression in the wilderness, and the more intensive commercial logging of the past, are also at play. Not as much timber now comes from national forests, he said, only about 2-3% of the nation’s total annual wood supply, but “it’s coming from the most sensitive forests we have left in this country.”
Hanson thinks taxpayer dollars would be better spent supporting more defensible space around homes, and doing some prescribed burns where appropriate.
“Science is telling us that beyond 100 feet from homes, there’s no additional benefit of any vegetation management in terms of home protection,” Hanson said.
Across national forests, Hanson said thinning projects are “killing and removing sixty, seventy, eighty percent of the trees in a given stand, including many mature and old growth trees.”
He has helped stopped some tree removals through the courts. Earlier this year, attorneys with Earth Island Institute got the Forest Service to limit some roadside hazard logging in the Sierra Nevada to trees within striking distance of motorists, instead of up to 200 feet away.
Wuenschel said the Forest Service isn’t planning logging projects in giant sequoia groves, but officials didn’t share how thinning differs from logging. One Forest Service article describes thinning this way: “Tools the Forest Service uses to thin tree stands include everything from hand tools to chainsaws and rakes, to the aforementioned heavy equipment which aside from cranes can include bulldozers and wood-chippers.”
The article, which features a photo of logs being stacked by a crane, starts by comparing the heavy machinery to a T. rex: “With the loud clang of metal hitting metal, you quickly realize this is no dinosaur, it’s a massive crane-like heavy equipment vehicle and it’s not eating trees, it’s removing them.”
Following the Castle Fire, officials described their work in giant sequoia groves in a much more thoughtful way, but few details were shared about future plans. Long-awaited new forest management plans for Sequoia and Sierra national forests that could be in effect for the next 15 years are still in the works.
Prescribed burns, where land managers light low-intensity fires, has been gaining more traction as a forest treatment. Hanson said the John Muir Project has never filed a lawsuit over prescribed fire, but he doesn’t talk it up, either.
He describes fire in Sierra forests this way: “If it hasn’t burned in a century, it doesn’t burn more intensely than if it hasn’t burned in 30 years. That’s a myth that it just gets more and more intense. But it is true that if an area burned eight years earlier or four years earlier, then it’s going to burn less intensely in a subsequent fire. So there is a temporary effect. And the thing is, when you have more fire, you’re just always going to have fires run into something that burned less than a decade ago.”
Brigham was diplomatic about it all.
“There are studies that show thinning can reduce fire intensities but there are also certainly areas that were thinned that burned under severe fire weather and burned at high intensity,” Brigham said. “No treatment works all of the time. Our current fire (KNP) appears to be having reduced fire intensity in areas that have previous wildfire or prescribed fire history, but fire is different than thinning.”
Fitzgerald said some of the groves that burned severely in the Windy Fire hadn’t experienced fire in decades, and then talked about how there had previously been “considerable fuels reduction work” in two groves with low-severity fire. Sprinklers were also installed there as the fire approached, she said. The ultimate goal is to “restore a natural fire regime in the groves,” Fitzgerald said, and to accomplish this, vegetation needs to be reduced to a level where prescribed fire is safe for giant sequoias, “and then we can begin a plan to have a program for repeated burning every ten to fifteen years.”
Even with climate change, Hanson sees the increase in high-intensity fire as within an acceptable, natural range of variability for Sierra wilderness, looking at historical levels of severe fire in the Sierra going back centuries.
Hotter fires will also create more patches of what he calls beneficial “snag forest,” where dead trees become an ecologically rich haven for a plethora of wildlife that’s comparable to old-growth forests in terms of biodiversity. Logs and broken tree trunks act like sponges, not tinderboxes, “they really don’t influence fire intensity,” Hanson said.
Even after years of drought and bark beetles killing trees, what he calls a natural part of the ecosystem, only about 12% of the forest currently is snag forest, Hanson said, which is “actually too little.” Historically, he said 22% to 39% of the forest in the Sierra Nevada was snag forest habitat at any point in time. Decades of fire suppression and aggressive logging, coupled with an overall “cool phase” for weather, he said, has given people an unnatural sense of what Sierra forests should look like.
“We had this illusion of invulnerability and this illusion of power that was never real, but we certainly thought it was for a long time, and a lot of people still haven’t gotten the memo on that.”
More snag forest, including some giant sequoias, is OK with Hanson. For his part at least, he can stand within a charred forest and smile at the new life he sees rising from the ashes.
“I love seeing this,” Hanson said as he admired many healthy giant sequoia saplings in Nelder Grove. “This gives me a lot of hope for the future because the thing is, we’re going to see more fire.”
This story was originally published November 19, 2021 at 5:00 AM.
