Science
Trees that survived L.A.’s wildfires are dying at alarming rate. Can they be saved?
The deadly fires that devastated homes in Pacific Palisades and Altadena also laid waste to a lush canopy of leaves and pine needles that had cooled and shaded residents here for generations.
Now, more than a year later, trees that had survived the flames are disappearing at a troubling rate.
Since the January 2025 fire siege, roughly 20% of surviving street trees have gone missing, according to preliminary results from a University of California research team.
Many of the hundreds of missing trees probably would have recovered from the damage they suffered in the fires, experts say.
Edith de Guzman cuts into the cambium layer of a carrotwood to see if it is green and healthy near Aiglon Plaza in Pacific Palisades.
The results from the survey of about 500 trees in the Palisades and 1,500 in Altadena — including conifers, palms, Chinese elms and carrotwoods — seem to confirm worrying patterns observed by arborists and local volunteers in the burn scars, who said losses will probably continue for years to come.
Several factors appear to be at work.
Even as the Palisades and Altadena rebuild, local governments only undertook limited efforts to water recovering trees. At the same time, building contractors have been quick to remove trees that stand in the way of construction, while debris removal crews have cut down living trees that they mistakenly identified as dead.
In response to the continuing loss of trees, a group of arborists and volunteers are working to keep the recovering trees alive — and hopefully someday start planting the next generation of the burn scars’ urban forests.
While many homeowners view trees through the lens of maintenance costs — regular pruning can be expensive, and tree roots can wreak havoc on sidewalks and underground pipes — the benefits of trees are numerous and well-documented, experts say.
The shade they provide and the process of evapotranspiration — where water on the surface of leaves evaporates and carries away heat similar to how human sweat works — can cool neighborhoods by more than 10 degrees. This cooling reduces the risk of heat illnesses and can lower homeowner energy costs.
Trees also improve air quality, improve residents’ mental health, and reduce the risks of flooding and landslides. Meanwhile, fire experts say that reasonably spread-out and well-maintained trees do not pose a significant fire risk.
Edith de Guzman, a climate change, water and urban forestry researcher with UCLA, has been studying the burn area trees with her team. The researchers did their first assessment in the months following the fire, and donned orange vests to do it again this past month.
Edith de Guzman uses a hypsometer to calculate the height of a tree in Pacific Palisades.
Their discovery that roughly two out of every 10 trees the team went back to check on were missing was particularly concerning to De Guzman because her team was only looking at public street trees — which the city and county have authority over and work to protect — as opposed to trees on private property, which are maintained or felled largely at the discretion of the property owners.
“On private property it’s a different story — except for protected species,” she said. Public trees, however, “we are still seeing removals that are unnecessary, and the city is not sure who is responsible.”
L.A. City Bureau of Street Services did not respond to a request for comment.
The fires themselves killed and damaged a significant fraction of the areas’ urban tree cover — both private and public — although precise estimates are hard to come by.
Almost immediately, the surviving trees faced trouble.
David Card, board president of the Palisades Forestry Committee, said shortly after the fire, trees began to fall. In the chaos of the aftermath, it was unclear what organizations — or what agencies — were responsible.
Rebecca Latta, co-founder of Altadena Green, said that when the U.S. Army Corps of Engineers debris removal efforts began, leadership worked with them to save trees but that the Army Corps’ contractors often pressured homeowners to approve tree removals and incorrectly identified native oak trees — which did not have leaves at the time — as dead.
Chinese elm trees rise over Pacific Palisades.
Once private contractors arrived to begin rebuilding, they often removed trees on private properties they determined were in the way — and sometimes even removed public street trees they did not have authority over, the advocates said.
At the same time, neither the city of Los Angeles nor the county have routinely watered surviving public trees — which arborists say is essential to helping damaged trees recover. The county did one round of watering in Altadena, but found it to be too expensive, Latta said. The city conducted no watering in the Palisades due to a lack of resources, according to Card.
L.A. County Public Works said it remains “committed to preserving the community’s public trees.” It routinely waters newly planted trees and will continue to assess the needs of mature street trees, the department added.
So, local groups are stepping up to save the trees.
The Forestry Committee began sending two watering trucks around the Palisades: a 2,000-gallon tanker from a landscaping company and a 500-gallon tank on the back of a trailer. Altadena Green began conducting property tree surveys to help residents understand which damaged trees would probably survive and how to take care of them.
The Forestry Committee is also working on a long-term tree planting program for the Palisades that will utilize fire-resilient tree species — although the Los Angeles Department of Water and Power asked the Forestry Committee to hold off for a year as it starts working to move power lines underground, Card said. Excavation will probably occur on plots where street trees are typically placed.
Researchers Oliver Khachikian, Matthew Murphy, Mariana Vargas and Sophia Riemer prepare to survey trees near Aiglon Plaza in Pacific Palisades.
In the meantime, saving existing trees remains the tree doctors’ priority.
Laura Travnitz, an Altadena resident who lost her home in the fire, recalled an Army Corps contractor pressuring her to remove more than a dozen fire-impacted trees on her lot. Now, they’re just stumps. Some already have little green shoots reaching up toward the sky.
“I’m 65,” she said. “I’m not going to be around for those to grow again.”
Nearly 500 feet up a near-vertical rock face, scraped clean of soil and alder trees, Bretwood Higman, a geologist, looked down across the Tracy Arm fjord in southeast Alaska at a scene of devastation.
At 5:26 a.m. on Aug. 10 last year, a mass of rock with a volume 24 times larger than that of the great pyramid of Giza crashed down the mountainside, sending a wave of water 1,578 feet up the opposite wall and setting off a tsunami that roared down the fjord. It swept over the ridge that Dr. Higman was now standing on. The whole thing took about a minute.
Dr. Higman was part of an international team investigating the aftermath of the geologic event, the second largest landslide-generated tsunami on record. Using computer models, the researchers were able to recreate the landslide and tsunami, as well as a standing wave called a seiche that sloshed back and forth for 36 hours after the landslide.
Among other things, the new study, published on Wednesday in the journal Science, revealed how tricky it is to predict such catastrophic landslides before they take place.
The Tracy Arm landslide was preceded by an unusually rapid retreat of the South Sawyer Glacier, leaving the rock slope that ultimately collapsed bare and unsupported. That same rearrangement of land elements is increasingly occurring throughout Alaskan fjords and around the world. As glaciers retreat and thawing permafrost lubricates slopes, these giant landslides may become more frequent.
Scientists have been sounding the alarm about the emerging hazards of climate-linked giant landslides in Alaska for years. In 2020, Dr. Higman discovered a slow-moving landslide in the Barry Arm fjord that he worried could collapse catastrophically and inundate the nearby town of Whittier with a tsunami.
“We’re rapidly approaching a totally new landscape that has way fewer glaciers in the Alps and really everywhere, and a lot of new lakes,” said Mylène Jacquemart, a glaciologist at ETH Zurich who was not involved in the study. She studied the Blatten landslide that buried a Swiss village in rock, ice and water last year.
Jackie Caplan-Auerbach, a seismologist at Western Washington University and an author on the new study, was among the first to hear about the tsunami: Her neighbors, whose boat was anchored at sea some 50 miles from the landslide, texted her about a strange surge of water that had hit their vessel. Other firsthand accounts trickled in from Harbor Island, where camping kayakers said their gear had been carried away by the wave, and from a 150-passenger cruise ship, the National Geographic Venture, that was sitting just outside the fjord.
The stakes are high for detecting these events ahead of time. Although no vessels were in Tracy Arm fjord proper when the landslide hit, that mostly came down to luck: It was early morning and not many boats were about.
But three large cruise ships carrying thousands of passengers and numerous small tour boats visit the fjord daily, ferrying tourists right up to the glacier’s calving face. Had the Venture been up the fjord, instead of at its mouth, the wave would have been “unsurvivable,” Dr. Higman said.
Increased cruise-ship tourism to glacial fjords, and more oil and gas exploration in the Arctic, mean “we, as a global society, are putting more infrastructure and people in harm’s way,” said Dan Shugar, a University of Calgary geomorphologist and the study’s lead author.
Scientists at the U.S. Geological Survey and its state counterpart in Alaska look for slopes along the vast coastline that are moving toward collapse, using satellite radar and optical imagery. Because resources are limited, only Barry Arm is monitored in real time, with on-the-ground scientific instruments. Detailed assessments of a handful more moving slopes are underway in Glacier Bay National Park, which is also frequented by cruise ships.
Dr. Shugar said Tracy Arm “throws a wrench in” the strategy of looking for slope deformation “because it happened, as far as we can tell, without much warning.” Scientists were unable to detect any deformation in the slope before the collapse.
But when Dr. Caplan-Auerbach dug deeper into the seismic data from the landslide, she noticed patterns of land movement similar to those that she had studied for decades, which sometimes preceded landslides on volcanic slopes.
These tremors were “probably tiny bits of slip on the base of the landslide, and it can do that only so much before it’s got to break apart and fall,” she said. Tiny coalescing fractures within the mountain eventually reach a crescendo, a threshold at which point the rock can no longer hold itself together, and the slope gives way.
It is not yet clear how many landslides display these seismic signals as precursors, but since there were no other cautionary signs, they provide a hope of early warning. If the signals are subtle — the slopes “whispering to us, not yelling,” as Dr. Caplan-Auerbach put it — it is possible the seismometer network in Alaska is spread too thin to typically pick them up.
“The bar is, can we do better than missing most of these,” said Noah Finnegan, a geomorphologist at the University of California, Santa Cruz, who was not involved in the study. “So getting a handle on why these precursors happen and what their relationship is to catastrophic collapse is an area many people are interested in.”
Last month, three cruise lines notified customers that their ships would not visit Tracy Arm this year, opting instead for nearby Endicott Arm and Dawes Glacier. “That’s probably a wise move, but there’s no reason why Endicott is any safer than Tracy,” Dr. Shugar said.
Stephen Hicks, a seismologist at the University College London and an author on the study, said the planet is entering a new era when warming has penetrated geology.
“When we think about climate change, we think about impacts in the atmosphere and rising sea levels,” he said. “We sort of look up and across, but we don’t often look down,” he added, but now “the ground has moved beneath all our feet.”
Many open questions remain. But among the biggest, Dr. Higman said, is whether we can expect a significant increase in such events as a result of climate change, as some studies suggest.
“If it’s a dice you roll every 50 years, well, maybe that’s all right,” he said. “But if it’s one you’re rolling once or twice a year, then this is really, really urgent.”
A 27-year-old woman began an experiment on herself early one morning in December 2024. Her laboratory was her childhood bedroom, tucked into a second-floor corner of a pale yellow house in the Boston suburbs. On a bookshelf behind her sat a small stuffed sloth and some favorite books, including “Siddhartha” by Hermann Hesse. Her parents were asleep in the room next door.
Her name is Rebecca, but she goes by Becks. Sitting at her desk in a gray T-shirt, she opened a small plastic bag filled with white powder. The bag was stamped “SR-17018,” and “NOT FOR HUMAN CONSUMPTION.”
She extracted some powder with a red microscooper, poured it onto a digital scale and carefully weighed out 25 milligrams. She gathered this into a blue and white pill capsule and sealed it, and then swallowed the capsule with water. It was 4:27 a.m.
“It’s my turn to be a guinea pig,” Becks wrote in the online diary she was keeping of her experience. In sharing her story with The New York Times, she asked that her last name not be used so potential employers don’t discover her drug history.
Becks had joined the vanguard of a dangerous, highly speculative do-it-yourself approach to getting sober. For a decade, on and off, she had been addicted to various drugs, most recently kratom, an opiate-like substance, which cleared her head and covered up her pain but required constant dosing. She feared the call of fentanyl, which she’d tried a few times.
“Every morning, I woke drenched in sweat from overnight withdrawals. It was a grim existence,” she wrote of her kratom use. She tried various methods to get sober, including three short inpatient detox stays and one monthlong rehabilitation treatment. She had periods of sobriety but couldn’t sustain it.
Then she heard about SR-17018, one of many new and unpredictable synthetic drugs made largely in China and sold online even though it is not approved or shown to be safe, and can pose lethal risks.
Most of these compounds, known as novel psychoactive substances, are designed to get people high. Among those substances, SR-17018 stands virtually alone in that people are using it to try to free themselves of addiction, and some claim it helps.
Excitement about SR-17018 grew after Reddit users discovered a 2019 study suggesting it could free drug-addicted mice of their dependence.
Days before the 2024 presidential election, future Health and Human Services Secretary Robert F. Kennedy Jr. posted a statement on X promising to end the U.S. Food and Drug Administration’s “aggressive suppression” of such alternative therapies as raw milk, ivermectin, psychedelics and, somewhat perplexingly, “sunshine.”
While the post did not explain how the FDA was limiting Americans’ access to the sun, many dermatologists were dismayed when Kennedy abruptly withdrew a proposed FDA rule that would have banned minors from using devices that mimic sunlight — indoor tanning lamps.
The rule, which was withdrawn March 16, would have also required indoor tanning facility users to sign a form acknowledging the risk of cancer, early skin aging and other health effects.
Kennedy’s action comes at a time when many adherents of his Make America Healthy Again movement have adopted regular sun exposure as a core principle of wellness, with social media influencers encouraging followers to abandon sunscreen and build up their “solar callus,” or sun tolerance, instead.
The trend has frustrated many dermatologists, who warn that the damage of frequent sunburns and tans accumulates over a lifetime, and those acquired early in life appear to play a disproportionate role in later risk of skin cancer. The Skin Cancer Foundation notes also that you cannot build up a tolerance to sun exposure and “there is no such thing as a ‘solar callus.’”
Dermatologists have long cautioned that indoor tanning lamps are no less dangerous, since they expose users to ultraviolet light at concentrations far above natural sunlight. Like sunlight, the lamps emit two different types of ultraviolet wavelengths: UVA, which are longer and penetrate more deeply into the skin, and UVB, which are shorter and more easily burn the outer layers.
Both light sources darken skin through the same biological process: UV rays change the structure and chemical profile of DNA in the skin, which then produces more melanin in order to prevent further damage.
A tanning bed session exposes users to UVB rays akin to those at noon at the equator — an intense experience, but at least one with a terrestrial equivalent, said Hunter Shain, an associate professor of dermatology at UC San Francisco. The UVA radiation in a tanning bed is roughly 15 times that found anywhere on the surface of the planet.
“They’re really blasting you with these super physiological doses of UV radiation that you couldn’t even find in a natural environment,” he said.
The World Health Organization counts UV-emitting tanning beds as a Group 1 carcinogen, alongside other known human carcinogens like tobacco cigarettes and asbestos. One study Shain co-authored found that tanning beds accelerate DNA mutations in parts of the body not typically exposed to the sun, leading to a nearly threefold increase in indoor tanners’ lifetime melanoma risk. Rates of melanoma diagnoses have increased by 46% in the last decade.
The tanning lamp rule, which was first proposed in 2015, focused on age as a specific risk factor. Tanning bed usage before the age of 35 is associated with a 75% increase in the risk of melanoma, the most serious and frequently fatal form of skin cancer.
The rule drew more than 9,000 public comments from both physicians and cancer research organizations supporting its implementation and from tanning bed industry representatives and business owners opposed.
Kennedy, who was photographed leaving a Washington tanning salon last year, was ultimately unconvinced of the need to ban minors from such establishments.
“In light of the scientific and technical concerns raised in the comments on the Proposed Rule, concerns regarding possible unintended consequences of certain proposals in the Proposed Rule, and potential alternatives proposed in comments received on the Proposed Rule, FDA is withdrawing the Proposed Rule in order to reconsider the best means for addressing the issues,” Kennedy wrote in the withdrawal letter.
Health and Human Services did not respond to questions about what scientific concerns and unintended consequences Kennedy was referring to.
Nineteen states (including California) and the District of Columbia have already banned people under 18 from indoor tanning salons. Roughly two dozen more have some kind of regulations regarding minors and indoor tanning, such as requiring parental permission or barring only younger children.
The collapse of the proposed federal ban has left many dermatologists disappointed.
“As you can see, when it’s left to the states, the implementation and the guardrails to minimize the exposure to carcinogens are not consistent. … Why are you going to default to a system that we know isn’t working correctly?” said Dr. Clara Curiel-Lewandrowski, chair of dermatology and co-director of the Skin Cancer Institute at the University of Arizona.
Minors in sun-baked Arizona are free to patronize indoor tanning establishments as long as they have a note from their parents. Curiel-Lewandrowski has treated many former sunbed enthusiasts for advanced melanoma in their 20s and 30s, she said.
“There’s a lot of regret. Regret for not knowing more, for not getting more help to understand the threat,” she said. “This is an age group that has a very hard time assessing risk. At that age, they don’t view carcinogens as a real threat.”
The U.S. is a bit of an outlier in its permissive approach to youth indoor tanning. Australia and Brazil have banned cosmetic indoor tanning entirely for people of all ages. Most western European countries ban minors from indoor tanning, as do most Canadian provinces.
“After the proposal lay dormant for more than a decade, I can’t say I was surprised to hear that the FDA withdrew it,” said Dr. Deborah S. Sarnoff, president of the Skin Cancer Foundation. “On the positive side, we made the public very aware of this issue, and this fight is far from over. We won’t be satisfied until tanning beds are banned in this country.”
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