June 14, 2024

Saving California’s kelp forests

Saving California’s kelp forests

Special report

California’s underwater forests have suffered a devastating decline. Now, the race is on to save them before it’s too late.

Watch the documentary

Watch our special report on how an army of purple urchins has decimated these ecosystems, threatening the marine life that depends on them and the ocean’s ability to help fight climate change. But there is hope.

Beneath the surface of the Pacific Ocean, where the cold California current sweeps down from British Columbia, lies a hidden forest of once-astonishing beauty. Known as “the sequoias of the sea” for their rich biodiversity and carbon storing prowess, the kelp forests of Northern California were home to hundreds of marine species, including whales, seals, octopuses and sharks — until recently.

Now they’re the scene of a plague, an invasion and a mass deforestation.

A marine heat wave in 2013 set in motion a series of events that would ravage the forest and destroy the habitat for much of that sea life.

First, warm waters are thought to have helped spread a disease that devastated the population of huge sunflower starfish that lived among the kelp. Then, without this voracious predator to control their numbers, purple sea urchins spread unchecked, feasting on the kelp forest and leaving behind a barren moonscape. Just 5% of the kelp forest remains.

The drama unfolding along this coast is what experts are calling a “climate-driven catastrophe” — one example of how global warming is threatening not only the health of the ocean and the marine life within it but its ability to absorb carbon and help regulate climate change.

The loss is so alarming, it’s mobilized a coalition of researchers, non-profits, urchin divers and others in a desperate race to protect the last remaining kelp forests and rebalance the ecosystem before it’s too late.

Kelp forest locations around the world

Modeled global distribution of the kelp biome


Touch and drag map to move


Kelp forests span nearly 25% of the world’s coastlines, with some of the most prolific found in the waters of South Africa, New Zealand and Australia, and along the west coast of the Americas.

“Kelp forests cover 360 million acres around the world, which is a footprint that’s five times larger than tropical coral reefs,” says Tom Dempsey, director of the California oceans program for The Nature Conservancy. “Like those coral reefs, kelp (forests) are the essential foundation for ocean health and resilience. They support a number of ecosystems and thousands of species from invertebrates to fish, seals and whales.”

Research shows that macroalgae or seaweeds worldwide, including kelp, store an estimated 173 million metric tons of carbon every year — equivalent to the annual CO2 emissions of 160 coal-fired power plants — most of which is deposited in the deep sea, permanently removing it from the atmosphere and helping to fight climate change. But all is not well with the world’s kelp forests.

Areas where kelp forests have experienced decline

These regions of decline represent surface canopy-forming kelp.


South Austalia Tasmania South Africa Central Chile Southern Norway North Sea Celtic Sea Scotian Shelf Gulf of Maine North-Central California Puget Sound Southern Aleutian Islands

Touch and drag map to move, tap on the dots to see the locations


Hover over the dots to see the locations

Pollution, climate change and overfishing have taken their toll on kelp worldwide. Some areas are experiencing extreme losses — Tasmania has lost over 95% of its giant kelp canopy and Norway’s coast has lost 80% of its kelp in recent decades. But few places have been as badly hit as Northern California.

In 2014, a giant expanse of warm water, which had gathered off the coast of Alaska the previous year, expanded all the way down the west coast to Mexico. Nicknamed “the blob,” this marine heat wave wreaked havoc on ocean ecosystems over the following two years, spurring harmful algal blooms and killing sea life like fin whales, sea otters and salmon.

While marine heatwaves can occur naturally, research has linked “the blob” directly to human-induced global warming. Its impacts have been devastating. California’s north coast has lost approximately 95% of its kelp canopy since 2014 over a 350-kilometer (217-mile) stretch of coastline, according to a recent study by researchers at the University of California, Santa Cruz.

Kelp systems are dynamic, often impacted by storms or cyclical weather systems like El Niño. Turnover is high but those watching kelp over the past decade have noticed this is not the usual boom-and-bust cycle.

“What we’re seeing right now, particularly up on the north coast, is fundamentally different,” says Dempsey. “We are seeing a climate-driven catastrophe with massive impacts to the ecology of that system, as well as the kelp-dependent communities up in the north coast and the larger state economy.”

He estimates that the kelp forests on the northern coast of California are worth hundreds of millions of dollars a year in terms of storm protection, carbon sequestration, fisheries services and tourism. Now, they have been laid to waste by purple sea urchins.

A native species, purple urchin populations exploded after one of its last remaining predators, the sunflower starfish, succumbed to a mass die-off starting in 2013. This army of ravenous purple urchins has eaten almost all the kelp, their primary food source, and created an expanse of urchin barrens — swathes of prickly, purple orbs as far as the eye can see.



Along the whole California coast, people are experimenting with different methods for removing urchin barrens. Southern California has seen these areas expand over the past century due to overfishing and a decline in the populations of other urchin predators. When The Bay Foundation, a non-profit environmental group based in Santa Monica, first started working on its Palos Verdes site near Los Angeles, purple urchin numbers had reached up to 100 per square meter — a healthy ecosystem usually has two.

“They were everywhere, they were on top of each other,” says Heather Burdick, The Bay Foundation’s director of marine operations. “It was terrifying to swim over it because you’re just afraid that you’re going to get spikes all over your body every time you’re doing surveys.”

These purple urchins have been described by researchers as “zombie-like” because they can survive in a starved state by lowering their metabolic rate, living for up to 50 years off algae that grows on rocks on the seafloor. In this state, with their insides shrunk to almost nothing, these starved urchins have no commercial value to divers and no nutritional value to other predators, which consequently ignore them.

The Bay Foundation hires local urchin divers to cull the almost empty purple urchins by smashing them with a hammer and leaving their shells to biodegrade, returning their nutrients to the seabed. While this may sound like an extreme form of conservation, the organization’s CEO, Tom Ford, says it is necessary given the lack of predators and the fact that urchin barrens don’t easily transition back to kelp forests.

Since 2013, they have helped restore 57 acres of kelp forest in the region through culling. Within a few months of starting the process, giant kelp had started to grow back and now the forest is thriving. “Just being able to swim under that canopy of kelp that didn’t exist in 2014 … it’s like a magical cathedral,” says Burdick.

Partly funded by non-profit Sustainable Surf’s SeaTrees program, it also provides an income for local urchin divers. With purple urchin populations demolishing the kelp, little food was left for more commercially valuable species like red urchins and abalone, forcing some local fisheries to close.

Purple urchins are much smaller than their red cousins and traditionally haven’t been worth fishing, until now. Enter the urchin ranchers.

Known as “California gold,” the state’s red sea urchins are a local specialty and renowned worldwide for their sweet taste. The gonads, or roe, are served in high-end restaurants across the globe going by their Japanese name — “uni.”

With red urchins in decline in California, a group of divers and entrepreneurs are looking for ways to make it economically viable to remove purple urchins. Santa Barbara urchin divers Stephanie Mutz and Harry Liquornik have teamed up with Doug Bush, the owner of a local aquaculture farm, to turn the worthless purple urchins into a sellable product.

Mutz and Liquornik fish for purple urchins off Santa Barbara’s Channel Islands and bring them to Bush’s farm, The Cultured Abalone, where he feeds them sustainably harvested seaweed for around 12 weeks until they have fattened up — a method referred to as “ranching.”

Bush says the ranched urchins are better quality than those found even in healthy kelp forests — on average 19 out of 20 ranched urchins will be full of roe.

“We essentially go from an empty shell to a little vessel full of delicate, perishable goodness in the space of about 12 weeks,“ Bush says. Mutz and Liquornik then sell the urchins directly to consumers and restaurants through their company, Sea Stephanie Fish. Bush says the response from foodies and chefs so far “has just been spectacular.”

A company doing this on a more global scale is Urchinomics, which has established urchin ranching facilities in California, Norway and Japan — all regions with widespread urchin barrens. It expects its first batch of commercially ranched urchins to go on sale in Japan at the end of July.

Some are skeptical that urchin fishing or culling can have a real impact on the scale of the urchin barrens, but Urchinomics founder and CEO Brian Tsuyoshi Takeda wanted to provide a “commercially driven, scalable solution” that could channel more funding into kelp restoration than traditional grants or philanthropy.

“We chose to build a restorative business model because we figured we as humanity have dug a hole sufficiently deep for ourselves that sustainability alone isn’t going to get us out of it,” says Takeda. “We built the entire business model around the idea that the more we profit, the better the environment becomes.”

The company hires commercial divers to fish the urchins and is working with conservation organizations like The Bay Foundation to ensure their efforts are targeted towards restoration. “We’re kind of like the economic motor that funds kelp restoration through the removal of urchins,” says Takeda.

But for restored kelp forests to thrive in the long-term, one thorny issue needs to be resolved — predators.

A colossus amongst sea stars, the sunflower starfish grows up to three feet (1 meter) wide, with over 20 arms and is one of the most voracious predators in the ecosystem. Found only from Alaska to Baja California, Mexico, sunflower sea stars swallow their prey whole, feasting on a diet of mussels, crabs, sea cucumbers, snails and sea urchins — helping to keep the populations in check.

Gliding along the seabed at surprising speed on their 15,000 tiny feet, these alien-like creatures “strike fear into organisms that they encounter,” says Jason Hodin, research scientist at Friday Harbor Laboratories, a research post of the University of Washington. “You can see organisms basically fleeing as they approach.”


Once abundant on the west coast of the United States, they succumbed to an epidemic of sea-star wasting syndrome starting in 2013 — a disease that makes their bodies melt into a pile of goo.

The event has been described by researchers as one of the largest marine die-offs ever recorded, killing what Hodin estimates to be a billion sea stars — including 90% of the entire sunflower sea starfish population, which are now listed as critically endangered. While the disease had been present in sea stars before 2013, researchers have linked the warming water temperatures at the time to the rapid spread and high mortality rate of the disease.

In partnership with non-profit The Nature Conservancy, Hodin and a team of researchers are working on the first-ever sunflower starfish captive breeding program, at their labs on San Juan island, off the coast of Seattle. In April, they announced the graduation of dozens of juvenile sea stars from larval stage to a mini sea stars, giving hope that they will survive to adulthood.

The eventual goal is to release them into the wild and help restore the lost populations, offering one natural solution to controlling purple urchin numbers, although Hodin is keen to stress this will need collective buy-in from state, federal, conservation and community organizations along the west coast.

Despite the daunting scale of the damage to these underwater forests, those involved in the rescue effort remain hopeful, in part due to kelp’s incredible ability to bounce back.

“It can be really hard to take a clear-eyed look at all of that without a deep sense of sadness, but this is something that we can solve,” says Dempsey. “If we harness the innovation and science and technology and market solutions that are close at hand and aim them at solving this big conservation challenge, we can do it. We can see that happen in our lifetime and that would be an immense achievement.”

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