Kelp Collapse in Northern California Waters Has Far-Reaching Impact

Loss of a vital nearshore ecosystem hurts fish, wildlife, and coastal communities

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Kelp Collapse in Northern California Waters Has Far-Reaching Impact
Kevin Joe
Northern California’s bull kelp forests are among the most productive ecosystems on the planet, providing nursery areas, food, and refuge for a variety of marine wildlife. But this habitat has been devastated by a warming ocean and a surge in the purple urchin population.
Kevin Joe/California Department of Fish and Wildlife

Editor's note: This article was updated on April 22, 2020, to correct information about the entity that released a kelp recovery plan.

Cynthia Catton was among the first marine scientists to witness the collapse of Northern California’s bull kelp forests, a decline that resulted in vast barren areas on the seafloor, piles of empty abalone shells, and the closure of abalone and red urchin fisheries and, finally, of the North Coast’s last diving shop.

“It is shocking, and devastating,” says Catton, a research associate in the Bodega Marine Laboratory at the University of California, Davis and a former California Department of Fish and Wildlife environmental scientist. “And I think it is a really big warning to all of us. There are big changes afoot, and we need to do things differently if we want things to be more predictable and more supportive of the ways of life we depend on.”         

The Pew Charitable Trusts spoke with Catton to learn more about her bull kelp work and the future of this vital nearshore ecosystem. This interview has been edited for clarity and length.

Cynthia Catton was captivated by the work of Jacques Cousteau when she was growing up and ultimately became a marine scientist and underwater photographer.
Lyle Britt

Q: What were the first signs that Northern California’s nearshore ecosystem was in trouble?

A: We saw wasting disease pretty much melting all the sea stars in 2013. In 2014, we noticed it was easier to swim though the bull kelp forest because there wasn’t as much kelp. And the water was warmer—too warm for our thick wetsuits. In terms of the ecosystem, we hadn’t noticed a big shift yet. There wasn’t anything particularly alarming besides the loss of sea stars.

Red abalone
Red abalone have been decimated by the loss of bull kelp off the coast of northern California over the last five years.
Dr. Steve Lonhart / NOAA MBNMS

Q: When did the situation become so dire?

A: Sometime between September 2014 and August 2015, things changed dramatically. We started seeing a lot of abalone, which normally would have been hidden, boogying across the rocks, looking for food. And purple urchins came out of their crevices instead of waiting for drift—pieces of kelp and other algae—to come by.

Q: What drove the big changes in abalone and urchin feeding behavior?

A: Abalone and urchins normally don’t move very far. They don’t have to, with blades of kelp and other algae drifting by. It’s like Door Dash for the ocean. But concurrent with the warmer water in 2014, bull kelp failed to grow, and adult urchins became a lot more aggressive. And purple urchins are really good at eating faster than other herbivores.

Purple urchins are proliferating in areas where bull kelp once thrived off the coast of Northern California.
Katie Sowul/California Department of Fish and Wildlife

Q: Why did the purple urchin population explode?

A: That’s an open question. Losing predatory sea stars probably supported the survival of many more urchins. And warm water is conducive to urchin survival and reproduction.

Q: What are the effects of bull kelp’s demise?

A: There are long-term consequences for the underwater ecosystem and for coastal communities and cultures. There are family traditions around red abalone fishing. And Native American tribes have traditional foods and decorations tied to abalone and kelp. This whole ecosystem is deeply embedded in their culture and spirituality. There’s a lot of grieving over this loss.

Kelp also supported a vibrant fishing economy: recreational fishing for red abalone and commercial fishing for red urchins. Now red urchins are not marketable because they are starving, and the commercial fishers needed federal disaster relief funds. The one remaining scuba shop on the North Coast—in Fort Bragg—shut its doors.

Kevin Joe
Even if Northern California bull kelp recovers, it may take a decade or more for abalone and other fisheries to bounce back.
Kevin Joe/California Department of Fish and Wildlife

Q: If bull kelp recovers, will abalone also come back?

A: Some abalone can recover, but it takes almost a decade for them to grow from larvae to a size they can be fished. And it will take a concerted, long-term effort to get their food and habitat to a more stable condition. So we aren’t talking about a quick bounce-back.

Q: What can people do?

A: You can educate yourself and support work we’ve already started. The Greater Farallones Association released a kelp recovery plan last April. I think it describes the issues well and identifies opportunities for different types of people to contribute.  

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