In one of the most comprehensive pictures yet of the growing health risks associated with wildfire smoke, new research suggests ash and soot from burning wildlands has caused more than 41,000 excess deaths annually from 2011 to 2020.

By 2050, as global warming makes large swaths of North America hotter and drier, the annual death toll from smoke could reach between 68,000 and 71,000, without stronger preventive and public health measures.

“The numbers are very big, and it definitely surprised us,” said Minghao Qiu, lead author and assistant professor at Stony Brook University. “We find that wildfire smoke is already killing a lot of people.”

During the 2020 wildfire season, the worst in California’s modern history, wildfires scorched more than 4.2 million acres statewide.

Many Californians, locked down during the COVID-19 pandemic, encountered choking air when they ventured outside. Bay Area residents remember the sickly orange sky they woke up to five years ago this month. The jet streams carried pollution thousands of miles east to the Atlantic Coast.

In the span studied, millions of people were exposed to unhealthful levels of air pollution. When inhaled, this microscopic pollution not only aggravates people’s lungs, it also enters the bloodstream, provoking inflammation that can induce heart attacks and stroke.

For years, researchers have struggled to quantify the danger the smoke poses. In the paper published in Nature, they report it’s far greater than public health officials may have recognized.

Yet most climate assessments “don’t often include wildfire smoke as a part of the climate-related damages. And it turns out, by our calculation, this is one of the most important climate impacts in the U.S.”

California, in particular, is projected to see the largest increase in smoke-related mortality, with over 5,000 excess deaths annually. The state’s vast forests and perennially dry climate make it the most fire-prone state in the nation. With 39 million residents, many Californians find themselves downwind.

The study also estimates a higher number of deaths than previous work in part because it projected mortality up to three years after a person has been exposed to wildfire smoke.

It also illustrates the dangers of smoke drifting from fire-prone regions into wetter parts of the country, a recent phenomenon that has garnered more attention with large Canadian wildfires contributing to hazy skies in the Midwest and East Coast in the last several years.

“Everybody is impacted across the U.S.,” Qui said. “Certainly the Western U.S. is more impacted. But the Eastern U.S. is by no means isolated from this problem.”

Elected officials and climate experts have called for reducing carbon emissions from burning fossils to prevent worsening effects from climate change. But because the concentration of greenhouse gases continues to climb each year and emissions are rising, not falling, some degree of warming is now unavoidable. Much of the carbon dioxide from a diesel tailpipe today, for example, will stay in the atmosphere for more than a century.

“Because of the inertia of the Earth’s [climate], even if we reduce the CO2 tomorrow, we are still going to see a considerable level of temperature increase,” Qiu said.

But that’s not to say nothing can be done. Qiu said it highlights the importance of adapting for a warmer planet, while working to reduce planet-warming emission.

Studies have shown air purifiers can drastically improve indoor air quality during wildfires. And states with a high fire risk, like California, should continue to fund prescribed burns, fires intentionally set by forestry professionals to clear away flammable vegetation and avoid larger wildfires.

“The tricky thing is, prescribed fires also generate smoke,” Qiu said. “So it’s going to be a trade-off. We are going to have some smoke, but the hope is it can reduce a much larger smoke burden due to [an actual] wildfire.”

The devastation left in the wake of January’s Eaton and Palisades fires was unimaginable. The firestorms engulfed 59 square miles of Southern California — more than twice the size of Manhattan — transforming entire city blocks in Altadena and Pacific Palisades into corridors of ashes, twisted metal and skeletal trees.

Federal disaster officials rapidly deployed thousands of workers to gather up the wreckage across the burn scars. Armed with shovels and heavy construction equipment, crews quickly collected fire debris from rugged cliffsides, dusky shorelines and sprawling burnt-out neighborhoods. In a matter of months, they transformed the heaps of charred rubble into mostly vacant matchbox lots, ready for rebuilding.

Recently, the U.S. Army Corps of Engineers reported that it had finished clearing roughly 2.6 million tons of wreckage from nearly 9,700 properties, an astonishing eight-month federal cleanup that has been extolled as the largest and fastest in modern American history. Private contractors removed fire debris from an additional 2,100 parcels.

However, many experts worry that the rapid pace of federal cleanup resulted in sloppy work, time-saving measures and lax oversight that may ultimately cost homeowners.

The Army Corps has largely demobilized and contractors have cleared out, and they’ve left serious questions for disaster victims who are preparing to embark on one of the region’s largest reconstruction campaigns in the past century.

Federal officials also notably disavowed the need to conduct soil testing, insisting it would be too time-consuming. But soil sampling performed by university researchers, local public health authorities and Los Angeles Times journalists have found excessive levels of toxic metals at properties already cleared by the Army Corps.

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A team of university scientists from UCLA, Loyola Marymount and Purdue tested soil samples from 47 already-cleaned homes in Altadena, finding 49% of already-cleaned homes still had elevated levels of lead above California’s standards for residential properties.

“This recovery cannot be credibly compared to any other wildfire cleanup in recent memory,” said Andrew Whelton, an engineering professor at Purdue University who studies natural disaster recovery. “And that is because of deliberate decisions by government officials at all levels to skip soil testing. They did not determine that when the contractors left a property, the property was safe to use.

“It’s not a recovery if you leave 50% of the properties unsafe. While the federal government may demobilize, the onus now has been pushed to the property owners to either finish the job. Or they can ignore it, because L.A. County doesn’t require your property to be safe to rebuild.”

Despite such concerns, many praise the effort for its efficiency. The speedy recovery has allowed some survivors, including Altadena resident Carlos Lopez, to rebuild much earlier than they anticipated.

“It’s hope,” Lopez said about his homesite, where, on Sept. 10, workers have already built a wooden frame. “Neighbors that I talked to, we just wanted something to grasp onto that we’re actually moving forward. There’s some realization that we can get back home sooner rather than later.”

Col. Jeffrey Palazzini, who oversaw debris removal operations for the Palisades fire, said the Army Corps and its contractors have largely received positive feedback from property owners, like Lopez. He said the speed is a reflection of the urgency of the public health threat, not necessarily an indication of poor workmanship.

Carlos Lopez is already starting to rebuild his home on the property he owns in Altadena, shown here in mid-September.

(Allen J. Schaben / Los Angeles Times)

The L.A. County wildfire cleanup marks the maturation of a federal wildfire response that has tackled a barrage of historically destructive fires in Oregon in 2020, New Mexico in 2022 and Hawaii in 2023 — each of which were the largest wildfires in their state’s history.

“Over the past seven to 10 years, I think there has been — sadly — enough experiences for this process to be streamlined and improved upon with lessons learned each time it happens,” said Laurie Johnson, a renowned urban planner who specializes in natural disaster recovery. “And I think L.A. has been a benefit of that.”

Lindsey Horvath, L.A. County supervisor representing the Palisades, expressed cautious optimism for the road ahead. “Throughout the cleanup, we’ve followed all recommended best practices and will continue to follow the advice of experts throughout our recovery,” Horvath said in a statement. “I continue to call for soil testing to give homeowners greater peace of mind before rebuilding, and support efforts to make recovery assistance more accessible so we can rebuild faster and safer. Recovery doesn’t end here.”

Early days

In Pacific Palisades and Malibu, the wildfires turned some of the region’s most famous stretches of roads — including Sunset Boulevard and Pacific Coast Highway — into an unrecognizable labyrinth of debris. Mansions with picturesque views of the Pacific Ocean were obliterated into charred slabs of stucco, broken concrete and dust.

In Altadena, a middle-class melting pot tucked into the foothills of the San Gabriel Mountains, the inferno consumed century-old cottages and family-owned businesses on Lake Avenue, the community’s main commercial drag.

In the wake of these twin disasters, Gov. Gavin Newsom’s administration asked the federal government to take the lead on recovery. In the final days of his administration, President Biden approved funding and deployed federal agencies to start removing and disposing the most dangerous materials from affected properties.

Jan. 9 aerial view of neighborhoods destroyed by the Palisades fire.

(Robert Gauthier / Los Angeles Times)

In mid-January, neighborhoods were a literal minefield of explosive materials, including propane tanks, firearm ammunition and large lithium-ion batteries in electric vehicles, e-bikes and blackout-ready battery storage systems. There were also a plethora of household items that contained corrosive acids and toxic ingredients that needed to be collected to prevent them from polluting soil and groundwater.

On Jan. 16, the Environmental Protection Agency deployed its first teams to assess the damage and presence of hazardous materials. The agency ultimately identified about 13,600 properties, mostly single-family homes, that had been damaged or destroyed in the fire, and probably rife with hazardous materials.

Within days of taking office, President Trump signed an executive order instructing the EPA to expedite the removal of hazardous materials. EPA administrator Lee Zeldin later said Trump had directed the agency to complete the mission in 30 days — a demanding directive for work that typically takes several months.

In response, the Federal Emergency Management Agency increased disaster funding by nearly $179 million, money used to “surge” 850 contractors to collect the most dangerous materials from the burn scars by that deadline, according to records obtained by The Times.

In white coverall suits and full-face respirators, hazmat workers went property by property sifting through the ashes to dredge up lead-acid batteries, tins of paint thinner and pesticide canisters.

EPA personnel and agency contractors converted popular community gathering spots, including the driving range of Altadena Golf Course and the parking lot of Will Rogers State Beach, into hazmat stockpile sites. Workers laid down multiple layers of plastic liners where materials could be sorted and eventually hauled to hazardous waste dumps.

EPA crews comb the ruins of a home on Miami Way that was burned in the Palisades fire.

(Robert Gauthier / Los Angeles Times)

On Feb. 25 — two days ahead of schedule — the EPA announced it had completed that work. Its hazmat crews had overseen the removal of 300 tons of hazardous debris from 9,400 properties — making it the largest-ever hazardous materials cleanup for a wildfire the EPA had ever executed.

However, the EPA had also passed over 4,500 parcels, or 30% of properties, deeming them unsafe to enter. A Times analysis of residential properties found that workers balked at accessing 1,336 homes damaged or destroyed in the Palisades fire, and 1,453 homes in the Eaton fire.

EPA spokesperson Julia Giarmoleo said the deferred properties had hazardous trees, dangerous obstructions, steep slopes and unstable walls that prevented the EPA field teams from safely accessing the property.

“EPA’s operations are always based on completing the entirety of our work as quickly, efficiently, and safely as possible,” Giarmoleo said. “In the case of the L.A. fires, EPA encountered a higher percentage of properties that required deferral due to partial structural destruction compared to previous EPA wildfire responses.”

The remaining hazmat work was, instead, left for the Army Corps of Engineers, the agency tasked with handling the second phase of debris removal.

The Army Corps rolls in

The Army Corps and its primary contractor, Environmental Chemical Corp., were charged with removing millions of tons of ash, concrete and metal. They vowed to remediate upward of 12,000 properties by January 2026 — within a year of when the deadly wildfires first broke out. The ambitious timeline would outpace any wildfire debris removal mission the Army Corps had ever tackled, including the 18-month recovery for the 2023 Lahaina wildfire that destroyed 2,200 homes and buildings.

Jan. 14 photo of Eliot Arts Magnet Middle School burned by the Eaton fire in Altadena.

(Jason Armond / Los Angeles Times)

The Army Corps and ECC hired several subcontractors, and in early February dispatched the first cleanup crews to several schools that were ruined in the fires, including Pasadena Rosebud Academy Charter School in Altadena, where hazmat workers shoveled asbestos waste into thick plastic bags. They waded through a field of charred debris, gathering up fire-gnarled steel rods, metal door frames and structural beams into piles, which were later loaded onto dump trucks and hauled away to landfills.

Soon after, workers moved onto fire-destroyed homes. In mid-February, after a two-day delay due to heavy rainfall, crews finished clearing their first homesites in Altadena and Pacific Palisades.

A view of Eliot Arts Magnet Middle School after the federal cleanup.

(Allen J. Schaben / Los Angeles Times)

As the cleanup progressed, one obstacle for public officials was tracking down the thousands of displaced survivors and getting them to sign paperwork that would grant federal cleanup crews permission to clear their properties. Because the fast-moving wildfires forced people to evacuate with little warning, many fled with only the clothes on their backs.

Army Corps personnel tried to disseminate sign-up instructions and appeal to the public at press conferences and community meetings. Local officials helped by making phone calls to disaster victims in parts of Altadena where response had been lacking, according to Anish Saraiya, Altadena’s recovery director for L.A. County Supervisor Kathyn Barger’s office.

“Our office even started calling individual property owners, because there was already a concern about the disparity postfire west of Lake [Avenue],” Saraiya said. “One of the things we wanted to make sure is that this was an equitable process that got to everybody at once. Obviously, someone will have to be last. But we wanted to make sure that process was transparent.”

Wildfire victims seek disaster relief services at one of two FEMA Disaster Recovery Centers at the Pasadena City College Community Education Center in Pasadena.

(Allen J. Schaben / Los Angeles Times)

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By April, with roughly 9,000 opt-ins, the federal cleanup had hit its stride. About 230 cleanup crews and 4,000 workers fanned out across the burn scars, working 12-hour shifts to remove debris from homes and haul it to landfills and scrapyards.

Following reporting by The Times, FEMA and the Army Corps drew criticism from environmental advocates and fire survivors for deciding not to perform soil testing after cleanups to ensure properties did not have toxic metals, such as lead, above California’s health standards for residential properties.

It would be the first major wildfire response in California since 2007 without a measurable goal for clearing toxic substances.

Homes destroyed by the Eaton fire were cleaned at a faster rate than those affected by the Palisades fire, according to a Times analysis of residential properties. Army Corps officials said they attempted to prioritize properties near schools, coastlines, waterways and occupied homes.

One such property belonged to Bronwen Sennish and her husband; their Spanish-style home had been a short distance from Palisades Elementary Charter School.

Sennish said she appreciated the sense of urgency and sensitivity with which the Army Corps approached her home. On one April morning, when she and her husband arrived at their lot, heavy machinery was already humming. Sennish said that the crew happily explained the parameters of their work. And the excavator operator took the time to sift through the rubble with the two in search for anything salvageable. “People who have been trained in the military are incredibly good at problem solving and logistics,” Sennish said.

But not everyone had a positive experience.

Cleanup crews, for example, excavated too much soil from Colten Sheridan‘s lot in northeast Altadena in April, according to internal Army Corps reports obtained by the Los Angeles Times. Sheridan, who is still displaced and living temporarily in Santa Cruz County, said he was never informed of the potentially costly mistake.

Instead, five months later, while Sheridan contemplated rebuilding plans, he was shocked to find out from L.A. Times journalists that his property had been the subject of a complicated internal debate within the Army Corps and debris removal workers.

“I feel like I absolutely should have been notified. I’m just reeling in my head right now,” he said. “If they over-excavated, and if they’re not going to do anything about it, what are my recourses? I don’t know.”

In early September, Sheridan called an Army Corps hotline dedicated to handling questions and concerns about the federal cleanup, but didn’t get answers.

A sign, put up on private property in Altadena, expressing community resilience as the federal cleanup was underway, on Sept. 10.

(Allen J. Schaben / Los Angeles Times)

A sign announcing that a new home will be built on a burned-out property in Altadena on Sept. 10.

(Allen J. Schaben / Los Angeles Times)

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Now Sheridan fears he may have to foot the bill to bring in clean soil and regrade his property before he can rebuild. If a home is seated too low, it won’t be able to properly connect sewer lines and storm drains, which require a high-to-low slope.

Army Corps officials declined to comment on Sheridan’s property, citing privacy concerns.

Many environmentalists and community members had worried the speed of the cleanup might lead to workers cutting corners or substandard workmanship.

Cleanup supervisors routinely observed workers without masks and other safety equipment, according to Army Corps records. In some cases, workers disregarded decontamination protocols by stepping outside of contaminated areas without rinsing their boots.

Jana Karibyna inspects a burned lamp in the backyard of her home after it was destroyed by the Eaton fire in February.

(Robert Gauthier / Los Angeles Times)

And according to internal documents attained by The Times, debris crews were regularly confused how to handle contaminated pool water — which researchers have found to contain trace amounts of lead, arsenic and other toxic chemicals. The contractors allegedly sprayed it into building footprints, front lawns, neighboring properties and even in the street, where it could have ended up in drainage systems leading to the oceans.

James Mayfield, owner of Mayfield Environmental Engineering, a private contractor specializing in hazardous materials, cleaned around 200 properties destroyed in the L.A. fires. For pools filled with ash, he suctioned contaminated water with a vacuum truck and sent it to locations that treat wastewater.

Mayfield believes inexperienced workers and the breakneck timeline probably led to some crews ignoring those best practices and redepositing toxic metals onto residential properties and local waterways.

“Proper hazmat disposal is about $10,000,” Mayfield said. “You can imagine, most people didn’t want to do that. They want to cut corners.”

Many wealthier homeowners with robust insurance policies opted out of the federal cleanup and decided to hire private contractors, which, in some cases, may have expedited their cleanup and rebuilding timeline, and provided access to services the government program didn’t provide — such as post-cleanup testing or property-wide soil removal.

A Times analysis of the private cleanups underscores the wealth gap between affluent residents of Pacific Palisades and working-class communities in Altadena: At least 1,392 homes opted out of the cleanup in the Palisades, nearly four times the number in the Eaton fire area, according to the analysis.

Tom James, a lifelong Palisades resident, decided that the Army Corps cleanup came with too many uncertainties. He also didn’t feel comfortable signing the liability waiver that would indemnify the federal government and contractors in the event of mistakes. He chose instead to hire a private crew that he was able to pay with his insurance policy, to clear out fire debris from his historic Victorian home in the heart of the Alphabet Streets, along with his collection of vintage cars and motorcycles in his garage underneath.

Still, James was affected by federal contractors. An Army Corps crew working next door left a large pile of his neighbors’ soil in his backyard. He walked down to the American Legion where Army Corps officials were stationed to let them know. A representative apologized and vowed to remove soil, but James said they never returned.

A time to rebuild

All told, the federal project cleared 9,673 properties — a mix of home sites, commercial properties, parks and schools — according to the Army Corps.

Aerial view of cleared properties and construction crews working on rebuilding a home after the federal cleanup of properties in Altadena following the Eaton and Palisades fires.

(Allen J. Schaben / Los Angeles Times)

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That has paved the way for the submission of more than 3,000 applications to rebuild — some 900 of which have already been approved.

In Altadena, some residents ready to rebuild have returned to their empty lots in RVs. The screech of tablesaws and popping of nail guns break up the silence in the fire-hollowed corners of these neighborhoods.

Lamar Bontrager, a real estate agent, has already laid a foundation and begun framing his home on Loma Alta Drive. He credits the Army Corps for the quick start.

“I had a very simple lot, and they took everything I wanted removed,” Bontrager said. Bontrager counts himself lucky. Looking at other lots around town, he said some neighbors will have a big lift. “At some houses, they [federal contractors] dug massive holes — my neighbor has a real issue to solve now with getting dirt back in.”

A fallen tree being prepared for removal from a destroyed property in Altadena. In the background, a construction crew works on rebuilding a home that burned down.

(Allen J. Schaben / Los Angeles Times)

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While the cleanup was the fastest in history, some survivors feel forgotten. According to federal records, 391 property owners who requested federal help were deemed ineligible by FEMA.

FEMA says some of those properties did not experience enough damage for eligibility. The agency deemed others, including many multi-family homes, as commercial properties, and, therefore, also ineligible.

These decisions put some of the largest housing developments affected by the fires in a bind. For example, the Army Corps cleared the Tahitian Terrace mobile home park in Pacific Palisades, across the street from Will Rogers State Beach, but did not clean up the Pacific Palisades Bowl, a 170-unit mobile home park next door.

Residents were never told why one property qualified and the other did not; those decisions are entirely up to FEMA.

Rusted metal frames and a blanket of pallid ash still sit within a few hundred feet from the ocean. Residents, who have heard little from the landowners about the dilemma, have been stuck in limbo.

“There’s hundreds and hundreds of people that are still having sleepless nights,” said one resident, Jon Brown, co-chair of the Palisades Bowl Community Partnership fighting for residents’ right to return home. “I just drove by the park today and it just makes me sick.”

Brown and others have watched the Corps clear thousands of lots and a handful of owners start rebuilding, while their piles of charred debris remained virtually untouched. They have little certainty they’ll ever be able to return.

Brown, facing steep rent for temporary housing, fears the owners may be looking for a way out — selling the land or changing its use.

“What is going to compel them to rebuild it as a mobile home park if they can’t even be motivated to clean it up?” Brown asked.

Federal disaster officials and contractors are no longer around to answer those questions.

Before the Army Corps and its workers packed up, they held two small ceremonies to commemorate the last homes to be cleaned in each burn scar.

In Altadena, Tami Outterbridge, daughter of renowned artist John Outterbridge, had specifically requested to be last.

Tami Outterbridge invited other artists to sift through the ashes of the property in hopes of finding objects they can use to create new artworks as tributes to her father.

(Robert Gauthier / Los Angeles Times)

She and her mother, Beverly, lived in two separate homes on their family’s lot in West Altadena. They postponed their cleanup several times, asking her father’s friends and contemporaries to help them scour the ashes for pieces of his artwork and other mementos. They found a pair of her father’s vintage spectacles and fragments of his sculptures, assembled from knickknacks and everyday objects.

When the cleanup crew arrived in mid-August, they came with a team of dog-assisted archaeologists that helped find her grandmother’s ashes — and recover some of John Outterbridge’s collection of flutes from underneath a collapsed wall.

“Those are things that literally are irreplaceable,” Tami Outterbridge said. “As I was reckoning with what it meant to say you’ve lost two homes and all your possessions — that’s when the idea started formulating. I can literally adhere to Dad’s art practice, which was very much about this notion of finding objects that other people saw as discarded — not worthy, trash debris — and turning them into aesthetic marvels.”

Stanley C. Wilson, a fellow artist and longtime friend of John Outterbridge, sifts through the ashes that remain of Outterbridge’s family home on June 8.

(Robert Gauthier / Los Angeles Times)

At the Aug. 14 ceremony commemorating Outterbridge’s home as the final Altadena home to be cleaned as part of the federal project, Saraiya, the Altadena recovery director, looked around at a neighborhood that just a few months ago had been chock-full of ash and cinders. It was now a sweeping panorama of mostly empty, mulch-covered lots.

“I’m not a very emotional person, but I felt myself getting choked up,” he said, “because it was really this one clarifying moment that this work is done.”

Saraiya said he understood local officials would need to soon start discussing rebuilding roads, installing underground power lines and planning a more fire-resilient community. “After all of these months, after all of this work and all of this effort — there’s so much more to do.”

Assistant data and graphics editor Vanessa Martinez and senior journalist Lorena Iñiguez Elebee contributed to this report.

The Trump administration plans to weaken environmental protections for threatened fish in California’s Sacramento-San Joaquin River Delta and pump more water to Central Valley farmlands, according to letters obtained by the Los Angeles Times.

The letters show Gov. Gavin Newsom’s administration strongly criticizing the Trump administration plan.

The U.S. Bureau of Reclamation recently notified California agencies that it plans to pump more water out of the delta into the southbound aqueducts of the federally operated Central Valley Project. That would send more water to farmlands and communities across the San Joaquin Valley.

The proposal advances a January executive order by President Trump and weakens protections for several kinds of fish whose populations have declined significantly in recent years.

Three state agencies objected to the plan in letters to the Bureau of Reclamation last month, signaling a new round of confrontation with the Trump administration over how California’s giant water systems should be operated.

The push to send more water to farms is supported by some growers in the Central Valley, who have long condemned state policies as harmful to agriculture. For years, drivers on the valley’s highways have seen their signs and billboards with slogans such as “Stop Dumping Our Farm Water & Jobs In the Ocean.” Trump has questioned why the state should keep more water in rivers to help “a tiny little fish” such as the delta smelt.

But California officials warned the Trump administration that pumping more water into the federal aqueducts will bring significant negative consequences for fish and the delta environment.

The federal proposal would increase water withdrawals in dry years as well as wet ones, leading to less water in the delta, which would cause “significant impacts to native fish species,” Diane Riddle, an official of the State Water Resources Control Board, said in one letter.

She said modeling estimates show that the Trump administration proposal would particularly harm fish during dry years, “when species are already stressed by dry conditions.”

State and federal pumping plants in the delta, which send water into the canals of the State Water Project and the Central Valley Project, often have to limit operation to leave enough water for threatened and endangered fish. Fish die when the massive pumps, which are powerful enough to regularly reverse the flow of water in the south delta, pull them into shallow waters, where they are easy prey for nonnative bass and other predators.

The California Department of Fish and Wildlife wrote that it is concerned about weakened protections for winter-run and spring-run chinook salmon, steelhead trout, delta smelt and longfin smelt.

Joshua Grover, deputy director of the agency’s Ecosystem Conservation Division, said what protective measures remain under the federal proposal are either vague, unworkable or not based on the “best available science.”

State officials warned that in addition to harming fish, the plan could force reductions to what the state can deliver to millions of people in Southern California cities.

The State Water Project, which delivers delta water to 27 million Californians and 750,000 acres of farmland, “could be forced to reduce water exports” because of the increased federal pumping, John Yarbrough, the Department of Water Resources’ deputy director, said in a letter.

He said that would occur because even if the federal government increases pumping, the state agency still must comply with the federal Endangered Species Act as well as the California Endangered Species Act.

The Trump administration plan brings new uncertainty for cities that depend on delta water and could upend the cooperation between state and federal water agencies that has been the norm for decades.

Yarbrough reminded Adam Nickels, the Bureau of Reclamation’s acting regional director in California, that state and federal agencies “have a long history and shared interest in working together to maximize California water supplies while also protecting the environment in a legally defensible manner.”

The disagreements between the Newsom and Trump administrations raise questions about the fate of joint state-federal efforts including the so-called voluntary agreements, a Newsom-backed plan to give water agencies more leeway in how they comply with delta water rules. If the federal government is no longer a willing partner, that would leave the plan in question.

The federal plan is called Action 5. Yarbrough urged the Trump administration “to reconsider Action 5 and comply with the legal requirements regarding environmental review, endangered species restrictions” and an agreement that for decades has guided coordination between the state and federal agencies.

Trump similarly tried to alter California water regulations and policies during his first term. But when his administration adopted water rules that weakened environmental protections in the delta, California and conservation groups successfully challenged the changes in court.

That cleared the way last year for the Biden administration, working together with Newsom’s administration, to adopt new rules for operating California’s main water delivery systems, which are among the largest in the world.

In his January executive order, Trump criticized what he called “disastrous” policies and water “mismanagement” by California, and directed federal agencies to scrap the plan that the Biden administration adopted.

Environmental and fishing groups have also condemned the Trump administration’s attempts to take more water from the delta, saying the goal is to prioritize political supporters in the agriculture industry above the needs of other water users and the health of waterways and fish.

“The Bureau of Reclamation is slashing protections for salmon and other species that are struggling,” said Barry Nelson, an advisor to the Golden State Salmon Assn., a nonprofit group that represents fishing communities.

“Some salmon runs and other species are on the brink of extinction, and commercial salmon fishing in California has been closed for three years,” Nelson said. “Cutting already weak protections further would be disastrous.”

Noting that Newsom has stood up to the Trump administration on other issues, he urged the governor to file a lawsuit “to block this clearly illegal federal decision.”