The Fight to Save the California Kelp Forest

In the warming waters of the Pacific Ocean, urchins crowd out a legacy ecosystem

By Joe Purtell

June 7, 2022


An urchin diver takes aim at a purple urchin in the Monterey Bay, California, on September 24, 2021. | Photo by Nina Riggio

I launch into the Pacific through a gap between two pillars of worn sandstone, sucked out to sea by the same swell that will one day reduce them to sediment. Buffeted by the surf, I rise with each wave and sink on the ebb until I am within arm’s reach of the rocks below, which are covered with quarter-inch strands of green seagrass that mirror my swaying movement. I keep my head down, kick hard, and breathe through my snorkel until I have passed through the mouth of the small cove into the open waters of the Monterey Bay.

It is my first time diving off the coast of Northern California, even though I was raised here. I follow the blue and white flash of my friend’s fins. The ocean is clear despite the turbulence, and I see a pastel underworld appear through white sheets of bubbles. Seaweed fronds flash ghostly blue, and dull orange spreads across rocks. Purple urchins cover boulders the size of pickup trucks—thin spines indifferent to the current.

I swim forward, bend at the waist, and dive, fighting down my instinct to panic as I descend into an unknown ocean. I kick furiously, the buoyancy of my wetsuit pulling me upward, until the resistance stops. When I look up, I am in another world, suspended in a valley between two large boulders, rocked back and forth by the slow pulse of waves that felt frantic on the surface. I am surprised to be lingering, not as breathless as I had imagined. I watch small fish pass, unconcerned by my presence. Then I swim to the surface, pull out my snorkel, and gasp for air. In the distance, I see the floating bulbs of a handful of kelp strands and wonder what this area looked like before the collapse.

Before 2013, canopies of kelp forests floated just offshore along the California coast from San Diego to Oregon. By 2019, 95 percent of kelp on the coast north of San Francisco was gone, and the Monterey Bay was in trouble. The causes of the collapse were manifold, but all indicative of the climate crisis and an epoch called the Anthropocene, Capitalocene, or Plantationocene, depending on the source. A patch of warm water created by a changing ocean climate reached nearly 2.5 million square miles in area at its peak in 2015 and stuck to the coast for three years. Kelp evolved in cold water, and the blob weakened the forests. At the same time, a wasting disease spread among sea stars, the sea urchin’s primary remaining predator along much of the California coast where otters were hunted to extinction. The simplified ecosystems of the North Coast, a stack of Jenga blocks already riddled with holes, were not able to absorb the shock of another missing piece. Urchins spread for hundreds of miles, eating the anchors that hold kelp to rock and setting the living structures that support one of the most diverse cold-water ecosystems in the world adrift to decay in warming seas.

“It’s like having a forest fire that’s running from Santa Barbara to Alaska, and no one even realizes it’s burning, and no one is trying to put it out,” said Keith Rootsaert, founder of the Giant Kelp Restoration Project (G2KR).

Butterfly House, the site of my first dive in the Pacific, used to be one of Rootsaert’s favorite spots, with a kelp canopy so thick you couldn’t swim straight out from shore. Now there are just a handful of the algal giants on a reef of urchin-covered rock. After watching the collapse, Rootsaert grabbed a hammer and started clearing urchins. A kelp forest is a collaboration of a hundred species and thousands of individuals helping each other or eating each other from holdfast to canopy. Rootsaert became one of them.

In her essay “A Threat to Holocene Resurgence Is a Threat to Livability,” the anthropologist Anna Tsing argues that dynamic ecologies like the kelp forest are the relics of an earlier epoch, the Holocene, a time before some people remade the world to promote only what was profitable. The ecologies of our current era are more fragile things, without the counterbalances required to stop ordinary creatures from becoming monstrous.

Purple sea urchins are not interlopers in the kelp forest. They have always lived in its nooks and crannies, where they eat the fallen fronds that drift into their hideaways. Without otters, sea stars, and sheepshead to keep them in their niche, the urchins become something else entirely. They spread until something stops them—and nothing does. Rootsaert estimates that kelp forests support 800 species of invertebrates and fish, while urchin barrens are home to just a few dozen.

“Welcome to the Anthropocene, in which alienated and disengaged organisms, including humans, multiply and spread without regard to multispecies living arrangements,” Tsing writes. “Such proliferation makes no adjustments for previous residents and shows no signs of limits.”

In Tsing’s conception, the Holocene and Anthropocene are both realities that share the same planet, sometimes the same bay. In these turbulent times, when forests become deserts and deserts become dust, when cattle plantations make rainforests pasture and peasant movements make plantations forests again, there is no one epoch that can describe our whole world. At least not yet—not while the Holocene ecologies that support a true diversity of life persist.

The underwater landscape of the Monterey Bay is a patchwork of forests and barrens—a place where you can swim from one epoch to another with a few kicks of your fins. You can also swim back.

“Welcome to the Anthropocene, in which alienated and disengaged organisms, including humans, multiply and spread without regard to multispecies living arrangements.”


The history of the Monterey Bay since the arrival of white settlers is a series of assaults and recoveries. In the 1800s, a rise in fur prices in Europe sparked an otter-hunting boom that drove the world’s smallest marine mammal to presumed extinction in California. With the otters gone, the people who had only just arrived in California turned to a new hunt and killed hundreds of whales a year until no more could be found. Abalone were next, then large fish, then shrimp, then sardines. They brought fish out of the bay and returned their ground-up guts, poisoning the waters that fed them. In a century, a Holocene ecosystem was destroyed and replaced by the barren waters of the Anthropocene.

But the Holocene lingered. A group of otters survived among the bays and inlets of Big Sur to the south and returned to Monterey a century after the hunting stopped. They cleared the seafloor and made way for kelp forests, aided by the people who instituted the first marine protections of the Monterey Bay.

“The regrowing forest is an example of what I am calling resurgence. The cross-species relations that make forests possible are renewed in the regrowing forest,” Tsing writes.

I visit my first kelp forest in a wide bay called Stillwater Cove, which shares parking with a golf course. Photographer Nina Riggio and I wade into the ocean from the end of a sandy beach below steep dirt cliffs runneled with memories of flowing water. As I swim out, the seafloor drops away, until it is barely visible at the edge of my 20 feet of visibility. We reach a kelp stand. The sun is out, and streaks of yellow light cross the stems of giant kelp like light through stained glass windows, lending the place a majesty not possible on a cloudy day. When I glance down, I am startled to find a young seal playing with my flippers. It takes an inquisitive bite at the tip of the spear I use for fishing. I dive below the canopy and wander through the halls of the kelp forest.

In her 2016 book Staying With the Trouble, Donna Haraway argues that collaboration across kind is the only way out of the Anthropocene. She believes that the creatures of earth, of which we are just one, do not precede their surroundings but are created in collaboration with them. An urchin in the Holocene is a grazer, a forager, and sometimes a snack. An urchin in the Anthropocene is a devastation.

“The Anthropocene is more of a boundary event than an epoch,” Haraway writes. “What comes after will not be like what came before. I think our job is to make the Anthropocene as short, thin, as possible, and to cultivate with each other in every way imaginable epochs to come that can replenish refuge.”

Keith Rootsaert’s G2KR is trying to do just that, working to clear the urchins off a section of Tanker’s Reef, by the city of Monterey, so that kelp can again grow in an area where it once thrived. Rootsaert has been diving on scientific and restorative projects since 2009 but started G2KR to inspire movement on a larger scale. The group trains divers, then gives them access to different coordinate assignments to clear urchins on their own time.

“When you start going down there and culling urchins, and it’s just a sea of urchins, it’s overwhelming. There’s just so many. It’s like taking a little brush and trying to paint a house,” Rootsaert said. “When you have a lot of people together, you’re encouraging each other. There’s somebody next to you doing the same thing, so you know your efforts are doubled, tripled.”

I join G2KR for a training dive, meeting the group at the Monterey dive shop Bamboo Reef and then heading to the beach with rented sets of scuba tanks and hammers. Our instructor, Nick Tah, has logged 2,000 dives in the Monterey Bay and watched his favorite forests be consumed in the last decade. He was Rootsaert’s first accomplice, diving off a motorboat to clear patches of reef as a two-man team. Now they are recruiting others, including the six of us gathered under overcast skies.

We descend an anchored line to the bottom of the bay, sinking into an ocean tinted green by the summer algae bloom. There is no kelp here, just urchins. We fan out into a line and move forward at a steady pace, puncturing the shell of each urchin we encounter. We traverse the long-tiered shelves of the shale reef, accompanied by foot-long spider crabs, blue nudibranchs, and a growing group of fish that have come to eat the dead urchins. The bottom of the Pacific is an eerie place, especially in the dim green light filtered through clouds and algae, but I feel better with these divers beside me, engaged in the same work. I smash 50 urchins before our tanks run low on air and we head back to shore.

Humans play only one part in Rootsaert’s master plan for Tanker’s Reef, filling a niche no other species does. By clearing urchins, we give the kelp space to grow, but the seeds themselves will be provided by a nearby stand.

“There’s a kelp forest right by the area we’re working in. So we’re trying to protect that so it can reseed our patch,” Rootsaert said.

Otters don’t eat urchins outside the kelp forest, because the dormant urchins lack the protein-rich insides that make negotiating their well-defended exterior worth it. But they love to eat healthy urchins within the forest. Sheepshead are rare in barrens but make kelp their home and also keep urchins in their holes. Once the forest is regrown, it will protect itself.

The presence of kelp refuges in Monterey is one reason Rootsaert believes restoration is more viable here than on the North Coast. Otters never made it back to the ocean north of the San Francisco Bay, unable to pass through the shark-patrolled waters of the White Triangle, as divers call it, which stretches between the seal-rich Farallon Islands, Santa Cruz to the south, and Jenner to the north. With the otters gone, abalone began to grow to an outrageous size, and trophy divers up from San Francisco paid good money to hunt the half-foot-long snails with opal shells.

Business interests opposed ecological ones, and now there are no abalone. The snails are grazers like urchins and live in the kelp forest. Unlike urchins, they cannot hibernate for years without food. By eliminating their common predator, business hopes to preserve a profitable fishery. But simplified ecosystems are more susceptible to collapse. By making the world a plantation for only the species that can be sold, we make ecosystems vulnerable to potential disaster. And disasters are coming more often.

“As long as we block out everything that is not human, we make sustainability a mean and parochial concept; we lose track of the common work that it takes to live on earth for both humans and nonhumans,” Tsing writes.

“I think our job is to make the Anthropocene as short, thin, as possible, and to cultivate with each other in every way imaginable epochs to come that can replenish refuge.”


The next time I go free diving, I am not hunting for fish. It is a rough day in Stillwater Cove, waves breaking in the bay. Hanging in the Pacific, I can see my fins but not much else. I swim in the five-foot bubble of my vision, the walls of my little world a sedimentary blue that reminds me of glacial lakes. Twisted shapes pass through those walls, kelp stalks, and their fronds. They are patchy here, but I am glad of each presence. It is shark season in the Pacific, and if I saw a great white at this distance, I wouldn’t have time to react.

I put away my spear gun and grab a pry bar. I swim to a boulder pocked with hundreds of holes, each containing a purple urchin. I dive and begin to remove them from the rock, tossed by waves breaking in the narrow channel as I work. I fill my bag with 20.

I swim into a patch of kelp on the leeward side of a small island, and the waves fade away. I can see farther in the forest, the sand kicked up by the surf not infiltrating as far into this protected grove on a rocky reef. The pastel pallet of the Pacific is again visible. I dive and swim by purple seaweed that covers boulders, the low leaves of iridescent blue seaweed that glint when struck by sunlight, orange and blue starfish, and the ghostly pearl skeletons of abalone. I am in a different world here, a different era, and one I much prefer.