Jon Holcomb is an old-time urchin diver with the leathery skin of a man who spends a lot of time on his boat. On a sunny morning in August, he motors out to a cove by the town of Mendocino, and squints across the water.

“This was solid kelp,” says Holcomb. “When we first came here in the mid-'80s, this was a complete mat, you couldn't swim through.”

And now?

“Well, it's devoid of kelp,” he says. “It's like a lake.”

For 42 years, Holcomb has made his living diving for red urchins. Their buttery insides are a delicacy in Japanese restaurants where they show up on menus as uni.

Holcomb shows the insides of an empty purple urchin, surviving without much kelp to eat. (Carrie Boyle/KQED)

Urchins live off kelp, and in the last three years the kelp forests on the Northern California coast have collapsed. Income for local red urchin divers has plummeted by 90 percent in three years.

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“Without kelp you lose all your shellfishery. You lose the abalone fishery, you lose the urchin fishery,” says Holcomb.

The kelp here has been devoured by a different kind of urchin: purple urchins. They’re smaller, less meaty and not worth fishing for. And they're voracious eaters of kelp.

“Nothing can survive their appetite,” says Holcomb.

Now, many parts of Northern California's coast have turned into what scientists call an urchin barren. There’s not much life besides a mass of spiny purple creatures carpeting the seafloor.

“These are starving animals that don’t die from starvation,” says Holcomb. “They just keep breeding and there’s more and more of them every year.”

A 'Perfect Storm'

Kelp beds play a key role in marine ecology. The fast-growing seaweed is a food source for many undersea animals. It also forms a habitat for young fish that hide in its stalks.

The size of kelp forests normally varies from year to year. But Cynthia Catton, a marine biologist with the California Department of Fish and Wildlife, says that in decades of observation, such low levels are unprecedented.

“We’re in a new phase,” says Catton.

So what happened?

Catton says that the kelp forests were hit by a “perfect storm” of factors. “The kelp forest has just gotten it from all sides.”

The first blow began in 2013, with a wasting disease that devastated sea star population along the entire Pacific Coast of North America. They are the urchins' main predator. With sea stars in decline, purple urchins went on a kelp-eating rampage.

“I have a friend who calls them the goats of the sea,” says Catton. “They form these feeding fronts and they just munch through everywhere they’re walking.”

The next problem: Kelp need cold water. In 2014, oceanographers noticed an unusual warming in the Northern Pacific -- even more than could be explained by climate science. For lack of a better term, they called it the “warm blob.” Then, last year’s El Niño made the water even warmer.

Catton’s team saw the kelp forests between the Bay Area and the Oregon border shrink by 93 percent.

Marine biologist Cynthia Catton meets divers Carson Bell and Jon Holcomb on a seafood processing dock in Fort Bragg. (Carrie Boyle/KQED)

Restoring the Kelp Forest

Shellfish divers are not always the closest allies with the agencies that monitor their fishing. As Jon Holcomb puts it, “we're resource users, and they're resource protectors.”

Now they share the same goal: restoring the kelp forest ecosystem.

Holcomb and a few other divers have volunteered to help biologist Catton with a restoration effort. They’ve been diving underwater to remove masses of purple urchins from a few test sites.

They're hoping that in those sites, their effort to remove urchins will allow kelp to grow back in the spring. The challenge is collecting thousands of urchins at a time.

Back out on his boat near Mendocino, Holcomb assembles the device he’s developed for just this purpose. He slaps together 10-foot-long pieces of fiberglass tubing to make a sort of underwater vacuum cleaner.

“Not real pretty,” he says, adjusting the tube. “I didn’t get carried away here on the aesthetics of this.”

It’s a modified version of a tool called an airlift, which is used to clear sand and silt from the seafloor. This one is built for purple urchins.

Holcomb puts on his scuba gear, and connects the pipes to an air compressor on deck. Then he dives down with the equipment to depths of about 30 feet.

In videos he’s made of his process, the seafloor looks like a minefield of spiky purple creatures.

Holcomb uses a little metal rake to scrape the urchins off the rocks, and into his fiberglass tube. The device sucks the urchins up, and deposits them into a large net.

This day, it takes him almost two hours to clear off an area smaller than a tennis court.

When he finally comes up, his net is packed with thousands of purple urchins with wiggly spines. They’re much lighter than the same number of urchins would be in a healthy kelp forest.

Holcomb smashes one open to show that there’s no flesh inside. “They’re all empty,” says Holcomb. “There’s no food value in them.”

Jon Holcomb, a veteran diver with his urchin airlift. (Carrie Boyle/KQED)

We head back to a dock in Fort Bragg, where Catton has brought a group of local volunteers to count and measure the urchins.

“We want to be able to say, ‘How much effort does this take?’ ” says Catton. “‘How effective is this on a small scale? How can we expand this effectively? And if not, what do we need to do differently?”

In a few months, her team will return to the test sites to find out if the divers’ efforts have allowed kelp to grow back. But even if their experiment succeeds, the problem of restoring the coastline is vast.

“It's much like trying to scratch the paint off a house with a pin,” says Holcomb. “It's not gonna be easy.”

Recently though, a few changes in the ocean may point towards a recovery for the kelp forest.

The warm blob in the Pacific has abated. The storms of the last few months have cooled off the ocean, and water temperatures are closer to normal.

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Additionally, many sea star populations along the coast appear to be recovering. If they survive to adulthood without dying of the wasting disease, they could help bring back the balance of the ecosystem -- eating the urchins that have been eating the kelp.

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