Science
How a water scientist hopes to save California habitats that could be pumped dry
California is recognized as one of the world’s hotspots of biodiversity, with more species of plants and animals than any other state. And a significant number of the state’s species, from frogs to birds, live in habitats that depend on groundwater.
These rich ecosystems — including spring-fed streams, wetlands, riparian forests and oak woodlands — are vulnerable to declines in groundwater levels. In areas where unchecked pumping from wells severely depletes aquifers, once-thriving wetlands and forests can dry up and die.
Spotting threats to vulnerable natural areas has become a mission for Melissa Rohde, a hydrologist who has spent years analyzing satellite data and water levels in wells to come up with strategies for preventing ecosystems from being left high and dry.
“Nature has been getting the short end of the stick. It basically gets whatever is left behind, which oftentimes is not enough,” Rohde said. “How do we ensure that these ecosystems are protected?”
More than 300 species of birds have been seen at Kern River Preserve.
(Robert Gauthier / Los Angeles Times)
California is the only state with a groundwater law that includes provisions intended to protect groundwater-dependent ecosystems. But the law, adopted in 2014, gives considerable leeway to local agencies in developing water management plans that prevent “significant and unreasonable adverse impacts.”
When Rohde and other scientists examined the local plans for parts of the state that fall under regulation, they found only about 9% of groundwater-dependent ecosystems are adequately protected, while the remaining 91% are vulnerable.
When they looked at the entire state, they determined only 1% of the ecosystems are sufficiently protected under measures adopted to date.
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Rohde has been focusing on finding ways to change that, in California and around the world.
Often working at home, she has pored over satellite data to spot decreases in vegetation greenness during drought, a telltale sign of die-off caused by declining aquifer levels. And she has analyzed how different types of trees, including willows, cottonwoods and oaks, fare when water levels fall depending on the depth of their roots.
Rohde and other researchers recently published a study outlining how California can set targets for maintaining groundwater levels — based on a formula including the type of vegetation, local water data and satellite imagery — to ensure the plants that anchor each ecosystem will be able to reach water and survive during dry times.
Cattle graze at the Kern River Preserve.
(Robert Gauthier / Los Angeles Times)
“If we don’t have groundwater levels that are able to support these diverse native vegetation ecosystems, then basically we run the risk of losing that important habitat for a lot of our threatened and endangered species,” Rohde said. “When you play around with keeping groundwater levels too deep to support the habitat, then you could lose species, and then that’s irreversible. The consequences can be severe.”
In California’s Mediterranean climate, trees, shrubs and the species they support are naturally adapted to drought. But excessive pumping from wells can push habitats beyond ecological limits by depleting the sources that sustain them.
With humanity’s heating of the planet intensifying droughts, the strains affecting these ecosystems continue to grow.
Already, California has lost the vast majority of its original wetlands to development, water diversions and agriculture. To avoid losing what remains, Rohde said, the state needs “a precautionary and preventative approach that can ensure that these ecosystems can withstand the intensification of droughts in climate change.”
During a recent visit to Kern County, Rohde and several conservation specialists walked in the shade through a lush forest of cottonwood trees near the south fork of the Kern River, visiting a nature preserve she had previously seen only in satellite images.
Scientist Melissa Rohde visits a riparian forest at the Kern River Preserve.
(Robert Gauthier / Los Angeles Times)
At the edge of a clearing, she came upon the bare, sunbleached skeletons of dead trees.
She said satellite data had revealed that parts of the forest died along this part of the Kern River during the drought between 2012 and 2016.
“That’s because the groundwater levels rapidly declined,” Rohde said.
After that die-off, she said, groundwater levels rebounded in the area, and the native vegetation has been growing back.
The Kern River Preserve protects the riparian ecosystem along the south fork of the Kern River.
(Robert Gauthier / Los Angeles Times)
It helps that this forest is protected as part of the Kern River Preserve, which is managed by the National Audubon Society, and that some nearby farmlands have been retired and converted to conservation lands over the years.
The preserve’s managers, working with the organization Ducks Unlimited, have also restored an expanded wetland by diverting water from the river and flooding a section of pastureland where cattle used to graze.
The wetland attracts birds, such as coots and tricolored blackbirds, and also recharges the aquifer that the roots of cottonwoods and willows tap into.
Scientist Melissa Rohde, left, and conservation specialists from Ducks Unlimited and the Audubon Society, including Reed Tollefson, right, stand on rocks overlooking a wetland at the Kern River Preserve.
(Robert Gauthier / Los Angeles Times)
The 3,300-acre preserve has expanded as adjacent alfalfa fields have been purchased and agricultural wells have been shut down, said Reed Tollefson, the preserve’s manager. These efforts have helped protect a refuge for birds including willow flycatchers and yellow-billed cuckoos.
As he pointed to several dead trees poking from the living cottonwoods, he said protecting the forest from groundwater pumping and climate change will require additional effort.
“I think it’s tenuous,” he said. “We’ve got more work to do to try and really sustain this.”
The dead trees that have appeared here and elsewhere in California over the past decade represent the sort of die-off that water managers need to focus on preventing, Rohde said.
“It has to be an intentional practice of setting thresholds, monitoring, using satellite data or other scalable means to measure the impacts, in order to make sure that we are not allowing this to happen on a wider scale,” she said. “From a biodiversity perspective, it’s absolutely critical.”
Rohde said she felt hopeful seeing the forest rebounding and much greener than it was several years ago, with many young trees coming up.
Some other parts of California haven’t fared nearly as well.
One rainy day last month, Rohde visited an area along the Santa Clara River in Ventura County where several hundred acres of willows and cottonwoods dried up and died during the drought in the mid-2010s.
When groundwater pumping by farms and communities caused aquifer levels to fall, many trees died along the river near the city of Fillmore.
“We saw this catastrophic drop in groundwater at this site,” Rohde said.
She visited the area with a research colleague and two managers from The Nature Conservancy. They stood on a gravel road next to a lemon grove, checking on what remained of the forest.
Scientist Melissa Rohde stands in a thicket of arundo, an invasive reed that has proliferated along parts of the Santa Clara River in Ventura County. There are ongoing efforts to remove the nonnative reeds in the area.
(Brian van der Brug / Los Angeles Times)
Where native trees died, an explosion of invasive reeds has taken over. The nonnative reeds, called arundo, have grown into thickets more than 20 feet tall. And unlike willows, Rohde said, arundo offers little value as habitat for birds.
“When we had that massive die-off, and the groundwater levels remained deep, there was no way for the native vegetation to regenerate,” she said. “But arundo is extremely efficient at extracting soil moisture. And so it was able to outcompete the native vegetation.”
She said efforts to prevent this sort of habitat degradation should be prioritized.
When managers of local agencies set goals for maintaining groundwater levels, she said, they can tailor targets to the type of vegetation — whether there are cottonwood trees, with roots averaging about 9 feet long, or oaks, with roots that average nearly 30 feet but can grow much deeper.
Her colleague Michael Bliss Singer said when native trees are ravaged by multiple years of low water levels, they will start losing leaves and then dropping branches.
In one study, Singer and others documented a “brown wave” of trees drying along the Santa Clara River between 2012 and 2016 — a loss they saw in satellite images.
Scientist Michael Bliss Singer looks out over the Santa Clara River in Ventura County.
(Brian van der Brug / Los Angeles Times)
“It’s completely transformed the ecosystem here,” said Singer, a professor at Cardiff University in Wales who is also a researcher at UC Santa Barbara.
When plants die off like this and don’t recover, it’s a symptom of an ecosystem in decline. To prevent more of these losses in an era when climate change is driving more severe droughts, Singer said, it’s crucial to “come up with creative solutions for the worst-case scenario.”
Rohde has found in her research, however, that most local groundwater plans in California haven’t adequately accounted for climate projections.
Previously, Rohde did other types of climate research, including a stint in Antarctica in 2010, where she was part of a drilling team collecting ice cores. From that experience, Rohde said she realized that “I didn’t want to spend my career convincing people that climate change was an issue; I wanted to do something about it.”
She wore a faded cap with an Antarctica map, a memento of that trip. Rohde said her recent work is motivated by concerns about the climate crisis and biodiversity, as well as a conviction that proactive steps to protect ecosystems can make a difference.
“I have two young kids. I really want to make sure that I’m doing the best thing that I can to ensure a sustainable future for them, where they can access nature,” Rohde said.
E.J. Remson, a senior project director for The Nature Conservancy, surveys a wetland along the Santa Clara River in Ventura County.
(Brian van der Brug / Los Angeles Times)
“Often groundwater is out of sight, out of mind,” she said. “We don’t measure it, we don’t understand it and we misuse it. And we need to make sure that we are managing groundwater so that it is supporting us, and making sure that we have a sustainable future.”
Rohde now works as an independent scientist. Previously, as a researcher for The Nature Conservancy, she helped write an atlas of threatened and endangered species that rely on groundwater.
California’s groundwater-dependent ecosystems lie not only along streams, but also in habitats such as mountain meadows, coastal redwood forests and mesquite bushes among desert sand dunes. The species they support range from tiger salamanders to desert pupfish, and from songbirds to mammals such as ground squirrels and bighorn sheep.
“The risks are high when species are on the verge of extinction,” Rohde said.
Rohde and other scientists have found that ecosystems sustained by groundwater are under threat worldwide. Some of the few regions that have measures intended to protect them, she said, include Australia, the European Union and California.
Still, even with California’s groundwater regulations and endangered species laws, Rohde said, “we continue to miss the mark in actually protecting them.”
Rohde said state officials should give local water agencies clear direction to ensure they’re using science-based methods to safeguard ecosystems in their state-mandated plans. She said agencies can now use the approaches scientists have outlined to map strongholds of biodiversity and set targets for maintaining aquifer levels.
“It’s very attainable,” she said. “Now, it’s just basically up to political will, or enforcement by the Department of Water Resources, to ensure that that happens.”
Walking in the rain at the Santa Clara River Preserve, Rohde followed her former Nature Conservancy colleagues Peter Dixon and E.J. Remson on a trail through a stand of healthy trees.
Peter Dixon, a project manager with The Nature Conservancy, walks on a trail through the riparian forest at the Santa Clara River Preserve.
(Brian van der Brug / Los Angeles Times)
They stood on the banks of the fast-flowing river, watching the muddy water churn past.
In the summer and fall, this part of the river usually dwindles to a trickle.
And during the next drought, when the river dries up, the forest will depend on the same groundwater that nearby communities and farms also use.
If the water needs of this and other ecosystems aren’t prioritized, Rohde said, vital habitats will suffer.
“We need to be deliberate about the planning, and ensuring that they get their fair share,” she said. “Their existence is potentially imperiled if we don’t act.”
Science
Commentary: My toothache led to a painful discovery: The dental care system is full of cavities as you age
I had a nagging toothache recently, and it led to an even more painful revelation.
If you X-rayed the state of oral health care in the United States, particularly for people 65 and older, the picture would be full of cavities.
“It’s probably worse than you can even imagine,” said Elizabeth Mertz, a UC San Francisco professor and Healthforce Center researcher who studies barriers to dental care for seniors.
Mertz once referred to the snaggletoothed, gap-filled oral health care system — which isn’t really a system at all — as “a mess.”
But let me get back to my toothache, while I reach for some painkiller. It had been bothering me for a couple of weeks, so I went to see my dentist, hoping for the best and preparing for the worst, having had two extractions in less than two years.
Let’s make it a trifecta.
My dentist said a molar needed to be yanked because of a cellular breakdown called resorption, and a periodontist in his office recommended a bone graft and probably an implant. The whole process would take several months and cost roughly the price of a swell vacation.
I’m lucky to have a great dentist and dental coverage through my employer, but as anyone with a private plan knows, dental insurance can barely be called insurance. It’s fine for cleanings and basic preventive routines. But for more complicated and expensive procedures — which multiply as you age — you can be on the hook for half the cost, if you’re covered at all, with annual payout caps in the $1,500 range.
“The No. 1 reason for delayed dental care,” said Mertz, “is out-of-pocket costs.”
So I wondered if cost-wise, it would be better to dump my medical and dental coverage and switch to a Medicare plan that costs extra — Medicare Advantage — but includes dental care options. Almost in unison, my two dentists advised against that because Medicare supplemental plans can be so limited.
Sorting it all out can be confusing and time-consuming, and nobody warns you in advance that aging itself is a job, the benefits are lousy, and the specialty care you’ll need most — dental, vision, hearing and long-term care — are not covered in the basic package. It’s as if Medicare was designed by pranksters, and we’re paying the price now as the percentage of the 65-and-up population explodes.
So what are people supposed to do as they get older and their teeth get looser?
A retired friend told me that she and her husband don’t have dental insurance because it costs too much and covers too little, and it turns out they’re not alone. By some estimates, half of U.S. residents 65 and older have no dental insurance.
That’s actually not a bad option, said Mertz, given the cost of insurance premiums and co-pays, along with the caps. And even if you’ve got insurance, a lot of dentists don’t accept it because the reimbursements have stagnated as their costs have spiked.
But without insurance, a lot of people simply don’t go to the dentist until they have to, and that can be dangerous.
“Dental problems are very clearly associated with diabetes,” as well as heart problems and other health issues, said Paul Glassman, associate dean of the California Northstate University dentistry school.
There is one other option, and Mertz referred to it as dental tourism, saying that Mexico and Costa Rica are popular destinations for U.S. residents.
“You can get a week’s vacation and dental work and still come out ahead of what you’d be paying in the U.S.,” she said.
Tijuana dentist Dr. Oscar Ceballos told me that roughly 80% of his patients are from north of the border, and come from as far away as Florida, Wisconsin and Alaska. He has patients in their 80s and 90s who have been returning for years because in the U.S. their insurance was expensive, the coverage was limited and out-of-pocket expenses were unaffordable.
“For example, a dental implant in California is around $3,000-$5,000,” Ceballos said. At his office, depending on the specifics, the same service “is like $1,500 to $2,500.” The cost is lower because personnel, office rent and other overhead costs are cheaper than in the U.S., Ceballos said.
As we spoke by phone, Ceballos peeked into his waiting room and said three patients were from the U.S. He handed his cellphone to one of them, San Diegan John Lane, who said he’s been going south of the border for nine years.
“The primary reason is the quality of the care,” said Lane, who told me he refers to himself as 39, “with almost 40 years of additional” time on the clock.
Ceballos is “conscientious and he has facilities that are as clean and sterile and as medically up to date as anything you’d find in the U.S.,” said Lane, who had driven his wife down from San Diego for a new crown.
“The cost is 50% less than what it would be in the U.S.,” said Lane, and sometimes the savings is even greater than that.
Come this summer, Lane may be seeing even more Californians in Ceballos’ waiting room.
“Proposed funding cuts to the Medi-Cal Dental program would have devastating impacts on our state’s most vulnerable residents,” said dentist Robert Hanlon, president of the California Dental Assn.
Dental student Somkene Okwuego smiles after completing her work on patient Jimmy Stewart, 83, who receives affordable dental work at the Ostrow School of Dentistry of USC on the USC campus in Los Angeles on February 26, 2026.
(Genaro Molina / Los Angeles Times)
Under Proposition 56’s tobacco tax in 2016, supplemental reimbursements to dentists have been in place, but those increases could be wiped out under a budget-cutting proposal. Only about 40% of the state’s dentists accept Medi-Cal payments as it is, and Hanlon told me a CDA survey indicates that half would stop accepting Medi-Cal patients and many others will accept fewer patients.
“It’s appalling that when the cost of providing healthcare is at an all-time high, the state is considering cutting program funding back to 1990s levels,” Hanlon said. “These cuts … will force patients to forgo or delay basic dental care, driving completely preventable emergencies into already overcrowded emergency departments.”
Somkene Okwuego, who as a child in South L.A. was occasionally a patient at USC’s Herman Ostrow School of Dentistry clinic, will graduate from the school in just a few months.
I first wrote about Okwuego three years ago, after she got an undergrad degree in gerontology, and she told me a few days ago that many of her dental patients are elderly and have Medi-Cal or no insurance at all. She has also worked at a Skid Row dental clinic, and plans after graduation to work at a clinic where dental care is free or discounted.
Okwuego said “fixing the smiles” of her patients is a privilege and boosts their self-image, which can help “when they’re trying to get jobs.” When I dropped by to see her Thursday, she was with 83-year-old patient Jimmy Stewart.
Stewart, an Army veteran, told me he had trouble getting dental care at the VA and had gone years without seeing a dentist before a friend recommended the Ostrow clinic. He said he’s had extractions and top-quality restorative care at USC, with the work covered by his Medi-Cal insurance.
I told Stewart there could be some Medi-Cal cuts in the works this summer.
“I’d be screwed,” he said.
Him and a lot of other people.
steve.lopez@latimes.com
Science
Diablo Canyon clears last California permit hurdle to keep running
Central Coast Water authorities approved waste discharge permits for Diablo Canyon nuclear plant Thursday, making it nearly certain it will remain running through 2030, and potentially through 2045.
The Pacific Gas & Electric-owned plant was originally supposed to shut down in 2025, but lawmakers extended that deadline by five years in 2022, fearing power shortages if a plant that provides about 9 percent the state’s electricity were to shut off.
In December, Diablo Canyon received a key permit from the California Coastal Commission through an agreement that involved PG&E giving up about 12,000 acres of nearby land for conservation in exchange for the loss of marine life caused by the plant’s operations.
Today’s 6-0 vote by the Central Coast Regional Water Board approved PG&E’s plans to limit discharges of pollutants into the water and continue to run its “once-through cooling system.” The cooling technology flushes ocean water through the plant to absorb heat and discharges it, killing what the Coastal Commission estimated to be two billion fish each year.
The board also granted the plant a certification under the Clean Water Act, the last state regulatory hurdle the facility needed to clear before the federal Nuclear Regulatory Commission (NRC) is allowed to renew its permit through 2045.
The new regional water board permit made several changes since the last one was issued in 1990. One was a first-time limit on the chemical tributyltin-10, a toxic, internationally-banned compound added to paint to prevent organisms from growing on ship hulls.
Additional changes stemmed from a 2025 Supreme Court ruling that said if pollutant permits like this one impose specific water quality requirements, they must also specify how to meet them.
The plant’s biggest water quality impact is the heated water it discharges into the ocean, and that part of the permit remains unchanged. Radioactive waste from the plant is regulated not by the state but by the NRC.
California state law only allows the plant to remain open to 2030, but some lawmakers and regulators have already expressed interest in another extension given growing electricity demand and the plant’s role in providing carbon-free power to the grid.
Some board members raised concerns about granting a certification that would allow the NRC to reauthorize the plant’s permits through 2045.
“There’s every reason to think the California entities responsible for making the decision about continuing operation, namely the California [Independent System Operator] and the Energy Commission, all of them are sort of leaning toward continuing to operate this facility,” said boardmember Dominic Roques. “I’d like us to be consistent with state law at least, and imply that we are consistent with ending operation at five years.”
Other board members noted that regulators could revisit the permits in five years or sooner if state and federal laws changes, and the board ultimately approved the permit.
Science
Deadly bird flu found in California elephant seals for the first time
The H5N1 bird flu virus that devastated South American elephant seal populations has been confirmed in seals at California’s Año Nuevo State Park, researchers from UC Davis and UC Santa Cruz announced Wednesday.
The virus has ravaged wild, commercial and domestic animals across the globe and was found last week in seven weaned pups. The confirmation came from the U.S. Department of Agriculture’s National Veterinary Services Laboratory in Ames, Iowa.
“This is exceptionally rapid detection of an outbreak in free-ranging marine mammals,” said Professor Christine Johnson, director of the Institute for Pandemic Insights at UC Davis’ Weill School of Veterinary Medicine. “We have most likely identified the very first cases here because of coordinated teams that have been on high alert with active surveillance for this disease for some time.”
Since last week, when researchers began noticing neurological and respoiratory signs of the disease in some animals, 30 seals have died, said Roxanne Beltran, a professor of ecology and evolutionary biology at UC Santa Cruz. Twenty-nine were weaned pups and the other was an adult male. The team has so far confirmed the virus in only seven of the dead pups.
Infected animals often have tremors convulsions, seizures and muscle weakness, Johnson said.
Beltran said teams from UC Santa Cruz, UC Davis and California State Parks monitor the animals 260 days of the year, “including every day from December 15 to March 1” when the animals typically come ashore to breed, give birth and nurse.
The concerning behavior and deaths were first noticed Feb. 19.
“This is one of the most well-studied elephant seal colonies on the planet,” she said. “We know the seals so well that it’s very obvious to us when something is abnormal. And so my team was out that morning and we observed abnormal behaviors in seals and increased mortality that we had not seen the day before in those exact same locations. So we were very confident that we caught the beginning of this outbreak.”
In late 2022, the virus decimated southern elephant seal populations in South America and several sub-Antarctic Islands. At some colonies in Argentina, 97% of pups died, while on South Georgia Island, researchers reported a 47% decline in breeding females between 2022 and 2024. Researchers believe tens of thousands of animals died.
More than 30,000 sea lions in Peru and Chile died between 2022 and 2024. In Argentina, roughly 1,300 sea lions and fur seals perished.
At the time, researchers were not sure why northern Pacific populations were not infected, but suspected previous or milder strains of the virus conferred some immunity.
The virus is better known in the U.S. for sweeping through the nation’s dairy herds, where it infected dozens of dairy workers, millions of cows and thousands of wild, feral and domestic mammals. It’s also been found in wild birds and killed millions of commercial chickens, geese and ducks.
Two Americans have died from the virus since 2024, and 71 have been infected. The vast majority were dairy or commercial poultry workers. One death was that of a Louisiana man who had underlying conditions and was believed to have been exposed via backyard poultry or wild birds.
Scientists at UC Santa Cruz and UC Davis increased their surveillance of the elephant seals in Año Nuevo in recent years. The catastrophic effect of the disease prompted worry that it would spread to California elephant seals, said Beltran, whose lab leads UC Santa Cruz’s northern elephant seal research program at Año Nuevo.
Johnson, the UC Davis researcher, said the team has been working with stranding networks across the Pacific region for several years — sampling the tissue of birds, elephant seals and other marine mammals. They have not seen the virus in other California marine mammals. Two previous outbreaks of bird flu in U.S. marine mammals occurred in Maine in 2022 and Washington in 2023, affecting gray and harbor seals.
The virus in the animals has not yet been fully sequenced, so it’s unclear how the animals were exposed.
“We think the transmission is actually from dead and dying sea birds” living among the sea lions, Johnson said. “But we’ll certainly be investigating if there’s any mammal-to-mammal transmission.”
Genetic sequencing from southern elephant seal populations in Argentina suggested that version of the virus had acquired mutations that allowed it to pass between mammals.
The H5N1 virus was first detected in geese in China in 1996. Since then it has spread across the globe, reaching North America in 2021. The only continent where it has not been detected is Oceania.
Año Nuevo State Park, just north of Santa Cruz, is home to a colony of some 5,000 elephant seals during the winter breeding season. About 1,350 seals were on the beach when the outbreak began. Other large California colonies are located at Piedras Blancas and Point Reyes National Sea Shore. Most of those animals — roughly 900 — are weaned pups.
It’s “important to keep this in context. So far, avian influenza has affected only a small proportion of the weaned at this time, and there are still thousands of apparently healthy animals in the population,” Beltran said in a press conference.
Public access to the park has been closed and guided elephant seal tours canceled.
Health and wildlife officials urge beachgoers to keep a safe distance from wildlife and keep dogs leashed because the virus is contagious.
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