When Jessica Fujii was in kindergarten, she drew a picture of her future. In a “What do you want to be when you grow up?” booklet, she skipped ballerina and veterinarian and wrote down something else entirely: sea otter biologist, complete with cartoon-like otters in the great tide pool at the Monterey Bay Aquarium.
Fujii grew up in California’s Bay Area, and trips to Monterey and its aquarium became a regular part of her childhood. She remembers paddling alongside her dad in a kayak on Monterey Bay, watching wild otters float on their backs as they cracked open crabs and let the shells sink. Back then, she mostly took their presence for granted.
Today, as a sea otter researcher and program manager at the aquarium, she knows how close California came to losing them – and how much now depends on the fragile population that remains. Along Northern California’s coasts, sea otters help habitats endure climate impacts like warming oceans, shifting predator ranges, and harmful algal blooms by keeping underwater plant life healthy and supporting resilient ecosystems.
Fujii is still focused on individual sea otters, but she’s also tracking a bigger picture of these important creatures over time.
A comeback story with a twist
From Fujii’s vantage point on Monterey Bay, southern sea otters – the subspecies that lives along the central California coast – are both a conservation success story and a reminder of what’s been lost.
Once hunted to near extinction for their fur, they survived off the coast of California thanks to a tiny remnant population and, later, federal protections and hands‑on conservation work. These days, there are only about 3,000 southern sea otters in California, and their geographical range has shrunk to roughly 13% of the coastline they historically occupied. Their numbers have been relatively steady for years, but their range hasn’t meaningfully expanded in about two decades.
Globally, sea otters live in coastal waters from Alaska across the North Pacific to Russia, but the southern sea otter is the only population found in California – and it’s the one scientists have studied most closely for its role in kelp forests, sea grass meadows, and coastal wetlands. And over the past several decades, scientists have learned that these animals punch far above their weight, especially along the nearshore strip where land and ocean meet.
From cuddly to keystone predator
It’s easy to see why sea otters are often treated like stuffed animals brought to life. Fujii describes a tiny, five‑pound pup as “basically a furball … it’s kind of like holding a kitten” before their teeth and jaws develop.
But the illusion only lasts so long. One longtime aquarium volunteer said he “wouldn’t want to be stuck in a pool with an adult otter.” It’s a good reminder that beneath the fluff is a muscular predator built to crush crabs and urchins.
Ecologists describe sea otters as a classic keystone species, an animal whose presence has much bigger impacts on its surroundings than its numbers alone would suggest. Unlike many other marine mammals, sea otters don’t have a thick layer of blubber to keep them warm. Instead, they rely on extremely dense fur and a very high metabolic rate.
“It’s about two times higher than similarly sized terrestrial mammals,” Fujii said, and because they can’t store energy as blubber, they need to be consuming those calories every single day.
That constant need to eat – up to a quarter of their body weight daily – helps explain why their foraging makes them major players in nearshore ecosystems. What, and how much, they eat ripples outward through food webs, shaping whether the coast is dominated by thick underwater forests and meadows, or by stripped-down, degraded seafloors that are more vulnerable to climate pressures.
Keeping kelp forests alive in a warming ocean
In recent years, a prolonged bout of unusually warm ocean conditions – made more likely and more intense by climate change – has caused kelp forests to crash along much of California, leaving behind vast “urchin barrens” where little grows besides hungry purple urchins. Around Monterey Bay, though, researchers found that sea otters ramped up their urchin eating in the remaining kelp beds, allowing those last patches of forest to hang on.
Left unchecked, urchins can mow down kelp beds and turn lush underwater forests into places where urchins have grazed away almost all the kelp. When otters are present and hunting, they thin out those urchins, giving kelp a chance to grow taller and thicker and to shelter a wide range of fish, invertebrates, and other marine life.
“Across much of their range, when sea otters consume urchins, they keep that population under control and limit how much grazing the urchins are doing on the kelp,” Fujii said. “That allows the kelp to flourish and be more abundant and provide homes for many other species.”
A recent study stitched together more than a century of kelp data along the California coast using old maps and satellite images. The analysis found steep losses in the floating kelp canopy in southern and northern regions where otters remain absent, but notable long‑term growth in kelp along the Central Coast – exactly where sea otter populations have rebounded.
Healthy kelp forests, in turn, absorb wave energy and soften the punch of storms that are projected to grow more intense with climate change, reducing erosion along vulnerable shorelines. Scientists are still debating how much long‑term carbon storage kelp forests actually provide, said Fujii, since much of that kelp washes ashore and decomposes.
But when otters keep kelp alive, they also maintain rich, complex coastal ecosystems that are better able to absorb climate shocks than bare seafloors.
In Elkhorn Slough, cleaning up blue carbon habitats
The otter’s climate story doesn’t end in the open‑coast kelp forests. As the ocean absorbs more than 90% of the excess heat from climate warming pollution and loses oxygen, many marine animals are struggling to cope with warmer, more acidic, less hospitable water. Coastal plants and algae – kelp, eelgrass, and other seaweeds – are emerging as unlikely allies, drawing down carbon, buffering waves, and giving stressed species places to hide and feed.
In sheltered estuaries like Elkhorn Slough, a coastal inlet where freshwater meets seawater just inland from Monterey Bay, researchers have found that sea otters can help keep underwater sea grass meadows and nearby marshes intact. Around a hundred otters now make their home in the slough, one of California’s last great coastal wetlands and a hot spot for birds, fish, and other marine life.
The connection runs through the food web: Otters eat crabs. When crab numbers drop, tiny grazers like sea slugs survive and multiply. These grazers don’t eat the sea grass; instead, they scrape away algae that builds up on the grass blades. That keeps the meadows healthy even in estuaries loaded with pollution from fertilizers and other runoff.
The marsh connection works differently. When shore crab numbers explode, the crabs burrow into marsh banks and chew on plant roots. That destabilizes shorelines and speeds up erosion. By eating those crabs, otters slow the loss of marsh edges that protect nearby communities from flooding and storm surge.
All of this matters for climate because sea grass beds and adjacent marshes are “blue carbon” habitats – coastal ecosystems that soak up and lock away carbon in plants and underlying sediments while also stabilizing shorelines and supporting fish and birds. California’s latest climate adaptation strategy explicitly calls out eelgrass as a blue‑carbon tool, part of a broader push to protect and restore coastal ecosystems that both store carbon and buffer people from rising seas.
Climate’s double edge: Ally and victim
Despite all the ways otters support coastal ecosystems, they’re not immune to the forces reshaping those places. Fujii and her colleagues have documented a sharp rise in sea otters injured or killed by white sharks – often juveniles that deliver a single, exploratory bite and don’t even eat the animal. Research she worked on has linked those juvenile sharks’ northward shift to warmer waters, a trend expected to continue as the ocean heats up. Aquarium researchers have also found that otters are more likely to be bitten in areas where the kelp canopy has thinned, potentially leaving them more exposed as they rest and forage near the surface.
At the same time, says Fujii, sea otters are increasingly exposed to harmful algal blooms that produce domoic acid, a harmful toxin. In otters, heavy exposure can cause sudden, fatal strandings, while lower‑level, chronic doses can quietly damage their hearts over time, leading to lethal heart disease years after an initial bloom has passed. Fujii also worries about more frequent and intense storms, which can separate moms and pups and leave tiny, still‑dependent otters stranded on beaches.
The species is bolstering coastal ecosystems against climate pressures, while facing mounting climate threats of its own.
Why protecting sea otters matters for everyone
In 2023, the U.S. Fish and Wildlife Service decided southern sea otters would retain protection under the Endangered Species Act, reflecting how vulnerable the population still is. Unlike many other listed species, though, they still don’t have an officially designated “critical habitat,” even though their nearshore environment is clearly central to their survival.
Without more room to grow or formal habitat protections, even a seemingly stable population can be vulnerable.
“As we continue to see the impacts of climate change, the stress on this population will continue to pile on,” Fujii said.
Even if they were immune to the impacts of climate change, sea otters clearly won’t solve the climate crisis on their own. They won’t erase emissions or single-handedly save the coast. But research over the past several decades has shown that they can shift the balance in the places they still inhabit, keeping kelp forests from collapsing into urchin barrens, maintaining sea grass meadows and salt marshes, and shoring up natural defenses that coastal communities will increasingly rely on as seas rise and storms intensify.
All this makes them more than just a charismatic species in need of saving.
“The hope is that by focusing on the recovery of this species, we can inspire protection of other animals and their habitats, and recognize the benefits people get when we protect those places,” Fujji said. “Basically, everyone wins when we protect otters.”
In a century defined by hard climate trade-offs, sea otters offer a reminder that some choices still deliver genuine win – wins: safeguard a beloved predator, and you safeguard the coastal habitats – and human communities – that depend on the same resilient, living shorelines.
Bonus: Sea otter cam
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