Science

Jeremiah Ostriker, Who Plumbed Dark Forces That Shape Universe, Dies at 86

Published

8 months ago

April 7, 2025

Jeremiah Ostriker, Who Plumbed Dark Forces That Shape Universe, Dies at 86

Jeremiah Ostriker, an astrophysicist who helped set off a revolution in humankind’s view of the universe, revealing it to be a vaster, darker realm than the one we can see, ruled by invisible forms of matter and energy we still don’t understand, died on Sunday at his home on the Upper West Side of Manhattan. He was 87.

His daughter Rebecca Ostriker said the cause was end-stage renal disease.

Over more than four decades, mostly at Princeton University, Dr. Ostriker’s work altered our understanding of how galaxies form and evolve as he explored the nature of pulsars, the role of black holes in the evolution of the cosmos and what the universe is made of.

Before the 1970s, most astronomers believed that galaxies were made up mostly of stars.

“Ostriker was arguably the most important single figure in convincing the astronomical community that this natural and seductive assumption is wrong,” David Spergel, the president of the Simons Foundation, which supports scientific research, wrote in 2022, nominating Dr. Ostriker, his mentor, for the Crafoord Prize, the astronomical equivalent of a Nobel. He cited Dr. Ostriker’s “eloquent advocacy for the then-radical new model in which the visible stars in galaxies were only a minor pollutant at the center of a much larger halo of dark matter of unknown composition.”

Dr. Ostriker’s work, he said, was “the grandest revision in our understanding of galaxies” in half a century.

Jerry Ostriker, as he was known to friends and colleagues, a man with a prickly sense of humor and a soft but commanding voice, was willing to go wherever the data and scientific calculations led him, and was not shy about questioning assumptions — or having fun. Prominently displayed in his home was a youthful photo of himself, taken in Cambridge, Mass., driving a motor scooter as his wife, Alicia Ostriker, seated behind him, lifts a bottle of wine to her lips. (A close look shows the cork still in the bottle.)

“He had the quickest wit of any scientist I have encountered,” said James Peebles, a Nobel physics laureate and a colleague of Dr. Ostriker’s at Princeton. “And I don’t remember ever matching him in a spontaneous debate” on any issue.

Asked in a 1988 oral history interview for the American Institute of Physics if he had favored any of the models of the universe being batted about in the 1970s, when he entered the field — whether the universe was finite or infinite, whether it had a beginning or was somehow always here, whether it would expand forever or crash back down in a big crunch — he said he had not.

“Scientists have followed their own biases, and my principle bias at the time was being contemptuous and intolerant of all of these people who had specific models,” he answered. “How could they be so certain when the evidence was as confusing and inconclusive?”

A ‘Classic Nerd Child’

Jeremiah Paul Ostriker was born on April 13, 1937, on the Upper West Side, the second of four siblings. His father, Martin Ostriker, ran a clothing company, and his mother, Jeanne (Sumpf) Ostriker, was a public-school teacher. Babe Ruth lived around the corner, and the children used to chase his car for autographs.

“I must have been the classic nerd child,” Dr. Ostriker wrote in a memoir published in the Annual Review of Astronomy and Astrophysics in 2016. He first became interested in science when he was 4: His mother started reading science books aloud to get him to sit still for an oil portrait, and the readings stuck.

After graduating from the Ethical Culture Fieldston School in the Bronx, Jerry Ostriker went to Harvard University, where he planned to study chemistry. Instead, he switched to physics, which appealed to what he called his “cosmic perspective.”

“I probably spent more time on literature than I spent on science,” he said in the oral history interview.

He soon began commuting to Brandeis University to visit Alicia Suskin, a former Fieldston classmate who was an aspiring artist and poet. They were married in 1958, while they were still undergraduates.

Ms. Ostriker, a professor emerita of English at Rutgers University, became an award-winning poet and has often written her husband into her work. In turn, he found poetry in astrophysics. “As an astrophysicist, you get a perspective on humankind,” he said, describing it as “sweating on this little grain of spinning sand.”

In addition to his wife and his daughter Rebecca, an editor for the opinion section of The Boston Globe, Dr. Ostriker is survived by two other children, Eve Ostriker, an astrophysicist at Princeton, and Gabriel Ostriker, a data engineer; a sister, Naomi Seligman; two brothers, Jon and David; and three grandchildren.

After graduating from Harvard in 1959, Dr. Ostriker worked at the United States Naval Research Laboratory for a year before enrolling in graduate school at the University of Chicago, splitting his time between the university’s Yerkes Observatory and the physics department, where he worked under the future Nobel laureate Subrahmanyan Chandrasekhar.

He earned his Ph.D. in 1964. After a postdoctoral year at the University of Cambridge in England, where he rubbed elbows with future black hole eminences like Stephen Hawking and Martin Rees, Dr. Ostriker joined Princeton as a research scientist. He remained there for 47 years, rising through the ranks to become chairman of the astronomy department and provost of the university.

The Dark Side of the Universe

At Princeton, Dr. Ostriker wrote a series of papers that would lead astronomy to the dark side.

He wondered whether galaxies, like stars, could break apart if they rotated too fast. The question was particularly relevant to so-called disc galaxies like the Milky Way, which are shaped sort of like a fried egg, with a fat, yolky center surrounded by a thin, white flat of stars.

Working with Dr. Peebles, he constructed a computer simulation and found that disc galaxies were indeed unstable. They would fall apart unless there was something we couldn’t see, a halo of some additional invisible mass, lending gravitational support.

Whatever this stuff called dark matter was — dim stars, black holes, rocks, exotic subatomic particles left over from the Big Bang — there could be a lot of it, as much as 10 times the mass of ordinary atomic matter.

It was one of the first theoretical arguments that there must be more to galaxies than could be seen in starlight. In the 1930s, the astronomer Fritz Zwicky had suggested that most of the mass in galaxies was “dark.” His idea was largely ignored until Dr. Ostriker and Dr. Peebles published their paper in 1973.

The reaction from the scientific community was predominantly hostile, Dr. Ostriker said. “I couldn’t see particularly why,” he said in the oral history. “It was just a fact.”

A year later, incorporating more data from galaxy clusters and other star systems, he and his colleagues argued that, in fact, most of the mass in the universe was invisible.

By the early 1980s, the idea of dark matter had become an accepted part of cosmology, but there remained conundrums, including calculations that suggested that stars were older than the universe in which they lived.

The missing ingredient, Dr. Ostriker and the theoretical physicist Paul Steinhardt, then at the University of Pennsylvania, suggested in 1995, was a fudge factor known as the cosmological constant. Einstein had come up with this concept in 1917, but had later abandoned it, considering it a blunder.

As Dr. Steinhardt recalled, he and Dr. Ostriker were “convinced that a universe with only dark and ordinary matter could not explain the existing observations.” But once they added the cosmological constant, everything came out right.

They were not the only ones with this idea. The cosmologists Michael Turner, now retired from the University of Chicago, and Lawrence Krauss, now retired from Arizona State University, also argued in favor of bringing back the constant. “To say Jerry was a giant in the field is an understatement,” Dr. Turner wrote in an email, adding, “Sparring with Jerry over science was a privilege and often a learning experience.”

Three years later, two competing teams of astronomers discovered that the expansion of the universe was being accelerated by a “dark energy” acting as the cosmological constant, pushing galaxies apart. The cosmological constant then became part of a standard model of the universe, as Dr. Ostriker and others had predicted.

In another series of papers, he and various collaborators transformed astronomers’ view of what was going on in the space between stars.

Dr. Ostriker and Renyue Cen, also of Princeton, concluded in 1999 that most ordinary atomic matter in the nearby universe was invisible, taking the form of intergalactic gas heated to millions of degrees by shock waves and explosions.

A Passion That Never Waned

At Princeton, Dr. Ostriker helped set up the Sloan Digital Sky Survey, a collaboration — initially of Princeton, the University of Chicago and the Institute for Advanced Study in Princeton, N.J. — aimed at remapping the entire sky in digital form with a dedicated telescope at Apache Point Observatory in Sunspot, N.M.

“The survey is going to increase our knowledge and our understanding of the universe a hundredfold,” he told The New York Times in 1991. “The map is not going to show us how the universe began, but it will show us the nature and origin of large-scale structure, the most interesting problem in astrophysics today. With an answer to this problem, we will be able to better approach the question of how it all began.”

The survey, started in 1998, is now in its fifth iteration and has generated some 10,000 research papers and archived measurements of a half-billion stars and galaxies, all free to any astronomer in the world.

As provost, Dr. Ostriker led the effort to vastly expand the university’s financial aid program, changing many loans to grants that would not need to be repaid, making a Princeton education more egalitarian. In 2000, he was awarded the National Medal of Science by President Bill Clinton.

Dr. Ostriker retired from Princeton in 2012, just as his daughter Eve was joining the astronomy faculty there. He took a part-time position at Columbia University, returning to his childhood neighborhood.

“Growing up in New York City, I couldn’t see the stars,” he once told The Times. He found them anyway, and a whole lot more that we can’t see with or without the glare of streetlights.

It was a passion that never waned. Encountered recently by a reporter on the sidewalk in front of Columbia, Dr. Ostriker launched into an enthusiastic description of a promising new theory of dark matter.

Early in 2023, by then ailing, he took to his bed at home. But he kept up with his research by email and had regular pizza lunches with colleagues.

Apprised recently of results from the James Webb Space Telescope that seemed to reinforce his ideas about dark matter, he wrote in an email to his colleagues, “Keep up the good work.”

The dark universe he helped conjure half a century ago has developed a few small cracks, leading to new ideas about the nature of that dark matter.

“It’s a very, very, very specific and clear theory. So therefore, God bless it, it can be wrong,” Dr. Ostriker said in a recent interview. “That’s the way science proceeds. And what we know about it is that it is a little bit wrong, not a lot wrong.”

Dr. Rees, a cosmologist at the University of Cambridge and the Astronomer Royal, summed up Dr. Ostriker’s life this way: “Some scientists come up with pioneering ideas on novel themes; others write definitive ‘last words’ on already-established topics. Jerry was in the first category.”

“He wrote among the earliest papers — now classics — on the nature of pulsars, the evidence for dark matter and on galaxy formation and cosmology. His flow of papers continued into his 80s,” Dr. Rees added. “He enthusiastically engaged in new data and in computational techniques. He inspired younger colleagues and collaborators, not just at Princeton but around the world.”

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Science

Notorious ‘winter vomiting bug’ rising in California. A new norovirus strain could make it worse

Published

9 hours ago

December 13, 2025

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Notorious ‘winter vomiting bug’ rising in California. A new norovirus strain could make it worse

The dreaded norovirus — the “vomiting bug” that often causes stomach flu symptoms — is climbing again in California, and doctors warn that a new subvariant could make even more people sick this season.

In L.A. County, concentrations of norovirus are already on the rise in wastewater, indicating increased circulation of the disease, the local Department of Public Health told the Los Angeles Times.

Norovirus levels are increasing across California, and the rise is especially notable in the San Francisco Bay Area and L.A., according to the California Department of Public Health.

And the rate at which norovirus tests are confirming infection is rising nationally and in the Western U.S. For the week that ended Nov. 22, the test positivity rate nationally was 11.69%, up from 8.66% two months earlier. In the West, it was even worse: 14.08%, up from 9.59%, according to the U.S. Centers for Disease Control and Prevention.

Norovirus is extraordinarily contagious, and is America’s leading cause of vomiting and diarrhea, according to the CDC. Outbreaks typically happen in the cooler months between November and April.

Clouding the picture is the recent emergence of a new norovirus strain — GII.17. Such a development can result in 50% more norovirus illness than typical, the CDC says.

“If your immune system isn’t used to something that comes around, a lot of people get infected,” said Dr. Peter Chin-Hong, an infectious diseases expert at UC San Francisco.

During the 2024-25 winter season, GII.17 overthrew the previous dominant norovirus strain, GII.4, that had been responsible for more than half of national norovirus outbreaks over the preceding decade. The ancestor of the GII.17 strain probably came from a subvariant that triggered an outbreak in Romania in 2021, according to CDC scientists.

GII.17 vaulted in prominence during last winter’s norovirus surge and was ultimately responsible for about 75% of outbreaks of the disease nationally.

The strain’s emergence coincided with a particularly bad year for norovirus, one that started unusually early in October 2024, peaked earlier than normal the following January and stretched into the summer, according to CDC scientists writing in the journal Emerging Infectious Diseases.

During the three prior seasons, when GII.4 was dominant, norovirus activity had been relatively stable, Chin-Hong said.

Norovirus can cause substantial disruptions — as many parents know all too well. An elementary school in Massachusetts was forced to cancel all classes on Thursday and Friday because of the “high volume of stomach illness cases,” which was suspected to be driven by norovirus.

More than 130 students at Roberts Elementary School in Medford, Mass., were absent Wednesday, and administrators said there probably wouldn’t be a “reasonable number of students and staff” to resume classes Friday. A company was hired to perform a deep clean of the school’s classrooms, doorknobs and kitchen equipment.

Some places in California, however, aren’t seeing major norovirus activity so far this season. Statewide, while norovirus levels in wastewater are increasing, they still remain low, the California Department of Public Health said.

There have been 32 lab-confirmed norovirus outbreaks reported to the California Department of Public Health so far this year. Last year, there were 69.

Officials caution the numbers don’t necessarily reflect how bad norovirus is in a particular year, as many outbreaks are not lab-confirmed, and an outbreak can affect either a small or large number of people.

Between Aug. 1 and Nov. 13, there were 153 norovirus outbreaks publicly reported nationally, according to the CDC. During the same period last year, there were 235.

UCLA hasn’t reported an increase in the number of norovirus tests ordered, nor has it seen a significant increase in test positivity rates. Chin-Hong said he likewise hasn’t seen a big increase at UC San Francisco.

“Things are relatively still stable clinically in California, but I think it’s just some amount of time before it comes here,” Chin-Hong said.

In a typical year, norovirus causes 2.27 million outpatient clinic visits, mostly young children; 465,000 emergency department visits, 109,000 hospitalizations, and 900 deaths, mostly among seniors age 65 and older.

People with severe ongoing vomiting, profound diarrhea and dehydration may need to seek medical attention to get hydration intravenously.

“Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy,” the CDC says. Sports drinks can help with mild dehydration, but what may be more helpful are oral rehydration fluids that can be bought over the counter.

Children under the age of 5 and adults 85 and older are most likely to need to visit an emergency room or clinic because of norovirus, and should not hesitate to seek care, experts say.

“Everyone’s at risk, but the people who you worry about, the ones that we see in the hospital, are the very young and very old,” Chin-Hong said.

Those at highest risk are babies, because it doesn’t take much to cause potentially serious problems. Newborns are at risk for necrotizing enterocolitis, a life-threatening inflammation of the intestine that virtually only affects new babies, according to the National Library of Medicine.

Whereas healthy people generally clear the virus in one to three days, immune-compromised individuals can continue to have diarrhea for a long time “because their body’s immune system can’t neutralize the virus as effectively,” Chin-Hong said.

The main way people get norovirus is by accidentally drinking water or eating food contaminated with fecal matter, or touching a contaminated surface and then placing their fingers in their mouths.

People usually develop symptoms 12 to 48 hours after they’re exposed to the virus.

Hand sanitizer does not work well against norovirus — meaning that proper handwashing is vital, experts say.

People should lather their hands with soap and scrub for at least 20 seconds, including the back of their hands, between their fingers and under their nails, before rinsing and drying, the CDC says.

One helpful way to keep track of time is to hum the “Happy Birthday” song from beginning to end twice, the CDC says. Chin-Hong says his favorite is the chorus of Kelly Clarkson’s “Since U Been Gone.”

If you’re living with someone with norovirus, “you really have to clean surfaces and stuff if they’re touching it,” Chin-Hong said. Contamination is shockingly easy. Even just breathing out little saliva droplets on food that is later consumed by someone else can spread infection.

Throw out food that might be contaminated with norovirus, the CDC says. Noroviruses are relatively resistant to heat and can survive temperatures as high as 145 degrees.

Norovirus is so contagious that even just 10 viral particles are enough to cause infection. By contrast, it takes ingesting thousands of salmonella particles to get sick from that bacterium.

People are most contagious when they are sick with norovirus — but they can still be infectious even after they feel better, the CDC says.

The CDC advises staying home for 48 hours after infection. Some studies have even shown that “you can still spread norovirus for two weeks or more after you feel better,” according to the CDC.

The CDC also recommends washing laundry in hot water.

Besides schools, other places where norovirus can spread quickly are cruise ships, day-care centers and prisons, Chin-Hong said.

The most recent norovirus outbreak on a cruise ship reported by the CDC is on the ship AIDAdiva, which set sail on Nov. 10 from Germany. Out of 2,007 passengers on board, 4.8% have reported being ill. The outbreak was first reported on Nov. 30 following stops that month at the Isle of Portland, England; Halifax, Canada; Boston; New York City; Charleston, S.C.; and Miami.

According to CruiseMapper, the ship was set to make stops in Puerto Vallarta on Saturday, San Diego on Tuesday, Los Angeles on Wednesday, Santa Barbara on Thursday and San Francisco between Dec. 19-21.

Science

Southern California mountain lions recommended for threatened status

Published

21 hours ago

December 12, 2025

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Southern California mountain lions recommended for threatened status

The California Department of Fish and Wildlife has recommended granting threatened species status to roughly 1,400 mountain lions roaming the Central Coast and Southern California, pointing to grave threats posed by freeways, rat poison and fierce wildfires.

The determination, released Wednesday, is not the final say but signals a possibility that several clans of the iconic cougars will be listed under the California Endangered Species Act.

It’s a move that supporters say would give the vulnerable animals a chance at recovery, but detractors have argued would make it harder to get rid of lions that pose a safety risk to people and livestock.

The recommendation was “overdue,” Charlton Bonham, director of the state wildlife department, said during a California Fish and Game Commission meeting.

It arrives about six years after the Center for Biological Diversity and Mountain Lion Foundation petitioned the commission to consider listing a half-dozen isolated lion populations that have suffered from being hit by cars, poisoned by rodenticides and trapped by development.

The following year, in 2020 the Commission found the request might be warranted, giving the lions temporary endangered species protections as “candidates” for listing. It also prompted the state wildlife department to put together a report to inform the commission’s final decision.

The next step is for state wildlife commissioners to to vote on the protections, possibly in February.

Brendan Cummings, conservation director for Center for Biological Diversity, hailed the moment as “a good day, not just for mountain lions, but for Californians.”

If the commissioners adopt the recommendation, as he believes they will, then the “final listing of the species removes any uncertainty about the state’s commitment to conserving and recovering these ecologically important, charismatic and well-loved species that are so much a part of California.”

The report recommends listing lions “in an area largely coinciding” with what the petitioners requested, which includes the Santa Ana, San Gabriel, San Bernardino, Santa Monica, Santa Cruz and Tehachapi mountains.

It trims off portions along the northern and eastern borders of what was proposed, including agricultural lands in the Bay Area and a southeastern portion of desert — areas where state experts had no records of lions, according to Cummings.

Officials in the report note that most of the lion groups proposed for listing are contending with a lack of gene flow because urban barriers keep them from reaching one another.

In Southern California, lions have shown deformities from inbreeding, including kinked tails and malformed sperm. There’s an almost 1 in 4 chance, according to research, that mountain lions could become extinct in the Santa Monica and Santa Ana mountains within 50 years.

The late P-22 — a celebrity mountain lion that inhabited Griffith Park – personified the tribulations facing his kind. Rat poison and car collisions battered him from the inside out. He was captured and euthanized in late 2022, deemed too sick to return to the wild because of injuries and infection.

For some species, protections come in the form of stopping chainsaws or bulldozers. But imperiled lions, Cummings said, need their habitats stitched together in the form of wildlife crossings — such as the gargantuan one being built over the 101 Freeway in Agoura Hills. He added that developments that could restrict their movement should get more scrutiny under the proposed protections.

Critics of the effort to list lion populations have said that it will stymie residential and commercial projects.

California is home to roughly 4,170 mountain lions, according to the recent report, but not all are equal in their struggle.

Many lion populations, particularly in northwest coastal forests, are hearty and healthy.

Protections are not being sought for those cats. Some, in fact, would like to see their numbers reduced amid some high-profile conflicts.

Bonham, the director of the state Department of Fish and Wildlife, spoke to concerns about public safety at the recent meeting, alluding to the tragic death of young man who was mauled by a cougar last year in Northern California.

“These are really delicate issues and the conversation I know in the coming years is going to have to grapple with all that,” said Bonham, who will be stepping down this month after nearly 15 years in his role.

California’s lions already enjoy certain protections. In 1990, voters approved a measure that designated them a “specially protected species” and banned hunting them for sport.

Science

California’s last nuclear plant clears major hurdle to power on

Published

1 day ago

December 12, 2025

Press Room

California’s last nuclear plant clears major hurdle to power on

California environmental regulators on Thursday struck a landmark deal with Pacific Gas & Electric to extend the life of the state’s last remaining nuclear power plant in exchange for thousands of acres of new land conservation in San Luis Obispo County.

PG&E’s agreement with the California Coastal Commission is a key hurdle for the Diablo Canyon nuclear plant to remain online until at least 2030. The plant was slated to close this year, largely due to concerns over seismic safety, but state officials pushed to delay it — saying the plant remains essential for the reliable operation of California’s electrical grid. Diablo Canyon provides nearly 9% of the electricity generated in the state, making it the state’s single largest source.

The Coastal Commission voted 9-3 to approve the plan, settling the fate of some 12,000 acres that surround the power plant as a means of compensation for environmental harm caused by its continued operation.

Nuclear power does not emit greenhouse gases. But Diablo Canyon uses an estimated 2.5 billion gallons of ocean water each day to absorb heat in a process known as “once-through cooling,” which kills an estimated two billion or more marine organisms each year.

Some stakeholders in the region celebrated the conservation deal, while others were disappointed by the decision to trade land for marine impacts — including a Native tribe that had hoped the land would be returned to them. Diablo Canyon sits along one of the most rugged and ecologically rich stretches of the California coast.

Under the agreement, PG&E will immediately transfer a 4,500-acre parcel on the north side of the property known as the “North Ranch” into a conservation easement and pursue transfer of its ownership to a public agency such as the California Department of Parks and Recreation, a nonprofit land conservation organization or tribe. A purchase by State Parks would result in a more than 50% expansion of the existing Montaña de Oro State Park.

PG&E will also offer a 2,200-acre parcel on the southern part of the property known as “Wild Cherry Canyon” for purchase by a government agency, nonprofit land conservation organization or tribe. In addition, the utility will provide $10 million to plan and manage roughly 25 miles of new public access trails across the entire property.

“It’s going to be something that changes lives on the Central Coast in perpetuity,” Commissioner Christopher Lopez said at the meeting. “This matters to generations that have yet to exist on this planet … this is going to be a place that so many people mark in their minds as a place that transforms their lives as they visit and recreate and love it in a way most of us can’t even imagine today.”

Critically, the plan could see Diablo Canyon remain operational much longer than the five years dictated by Thursday’s agreement. While the state Legislature only authorized the plant to operate through 2030, PG&E’s federal license renewal would cover 20 years of operations, potentially keeping it online until 2045.

Should that happen, the utility would need to make additional land concessions, including expanding an existing conservation area on the southern part of the property known as the “South Ranch” to 2,500 acres. The plan also includes rights of first refusal for a government agency or a land conservation group to purchase the entirety of the South Ranch, 5,000 acres, along with Wild Cherry Canyon — after 2030.

Pelicans along the concrete breakwater at Pacific Gas and Electric's Diablo Canyon Power Plant

Many stakeholders were frustrated by the carve-out for the South Ranch, but still saw the agreement as an overall victory for Californians.

“It is a once in a lifetime opportunity,” Sen. John Laird (D-Santa Cruz) said in a phone call ahead of Thursday’s vote. “I have not been out there where it has not been breathtakingly beautiful, where it is not this incredible, unique location, where you’re not seeing, for much of it, a human structure anywhere. It is just one of those last unique opportunities to protect very special land near the California coast.”

Others, however, described the deal as disappointing and inadequate.

That includes many of the region’s Native Americans who said they felt sidelined by the agreement. The deal does not preclude tribal groups from purchasing the land in the future, but it doesn’t guarantee that or give them priority.

The yak titʸu titʸu yak tiłhini Northern Chumash Tribe of San Luis Obispo County and Region, which met with the Coastal Commission several times in the lead-up to Thursday’s vote, had hoped to see the land returned to them.

Scott Lanthrop is a member of the tribe’s board and has worked on the issue for several years.

“The sad part is our group is not being recognized as the ultimate conservationist,” he told The Times. “Any normal person, if you ask the question, would you rather have a tribal group that is totally connected to earth and wind and water, or would you like to have some state agency or gigantic NGO manage this land, I think the answer would be, ‘Hey, you probably should give it back to the tribe.’”

Tribe chair Mona Tucker said she fears that free public access to the land could end up harming it instead of helping it, as the Coastal Commission intends.

“In my mind, I’m not understanding how taking the land … is mitigation for marine life,” Tucker said. “It doesn’t change anything as far as impacts to the water. It changes a lot as far as impacts to the land.”

The deal has been complicated by jurisdictional questions, including who can determine what happens to the land. While PG&E owns the North Ranch parcel that could be transferred to State Parks, the South Ranch and Wild Cherry Canyon are owned by its subsidiary, Eureka Energy Company.

What’s more, the California Public Utilities Commission, which regulates utilities such as PG&E, has a Tribal Land Transfer Policy that calls for investor-owned power companies to transfer land they no longer want to Native American tribes.

In the case of Diablo Canyon, the Coastal Commission became the decision maker because it has the job of compensating for environmental harm from the facility’s continued operation. Since the commission determined Diablo’s use of ocean water can’t be avoided, it looked at land conservation as the next best method.

This “out-of-kind” trade-off is a rare, but not unheard of way of making up for the loss of marine life. It’s an approach that is “feasible and more likely to succeed” than several other methods considered, according to the commission’s staff report.

“This plan supports the continued operation of a major source of reliable electricity for California, and is in alignment with our state’s clean energy goals and focus on coastal protection,” Paula Gerfen, Diablo Canyon’s senior vice president and chief nuclear officer, said in a statement.

But Assemblymember Dawn Addis (D-Morro Bay) said the deal was “not the best we can do” — particularly because the fate of the South Ranch now depends on the plant staying in operation beyond 2030.

“I believe the time really is now for the immediate full conservation of the 12,000 [acres], and to bring accountability and trust back for the voters of San Luis Obispo County,” Addis said during the meeting.

There are also concerns about the safety of continuing to operate a nuclear plant in California, with its radioactive waste stored in concrete casks on the site. Diablo Canyon is subject to ground shaking and earthquake hazards, including from the nearby Hosgri Fault and the Shorline Fault, about 2.5 miles and 1 mile from the facility, respectively.

PG&E says the plant has been built to withstand hazards. It completed a seismic hazard assessment in 2024, and determined Diablo Canyon is safe to continue operation through 2030. The Coastal Commission, however, found if the plant operates longer, it would warrant further seismic study.

A key development for continuing Diablo Canyon’s operation came in 2022 with Senate Bill 846, which delayed closure by up to five additional years. At the time, California was plagued by rolling blackouts driven extreme heat waves, and state officials were growing wary about taking such a major source of power offline.

But California has made great gains in the last several years — including massive investments in solar energy and battery storage — and some questioned whether the facility is still needed at all.

Others said conserving thousands of acres of land still won’t make up for the harms to the ocean.

“It is unmitigatable,” said David Weisman, executive director of the nonprofit Alliance for Nuclear Responsibility. He noted that the Coastal Commission’s staff report says it would take about 99 years to balance the loss of marine life with the benefits provided by 4,500 acres of land conservation. Twenty more years of operation would take about 305 years to strike that same balance.

But some pointed out that neither the commission nor fisheries data find Diablo’s operations cause declines in marine life. Ocean harm may be overestimated, said Seaver Wang, an oceanographer and the climate and energy director at the Breakthrough Institute, a Berkeley-based research center.

In California’s push to transition to clean energy, every option comes with downsides, Wang said. In the case of nuclear power — which produces no greenhouse gas emissions — it’s all part of the trade off, he said.

“There’s no such thing as impacts-free energy,” he said.

The Coastal Commission’s vote is one of the last remaining obstacles to keeping the plant online. PG&E will also need a final nod from the Regional Water Quality Control Board, which decides on a pollution discharge permit in February.

The federal Nuclear Regulatory Commission will also have to sign off on Diablo’s extension.