An Ecosystem in Crisis: The Movement to Save the Disappearing Kelp Forests in Northern California

For thousands of years, thick canopies of bull kelp formed an underwater forest spanning the foggy coast of Northern California. Bull kelp is the cornerstone of a rich subtidal community, providing food and habitat for creatures like abalone, sea stars and rockfish.  But in recent years, shocking changes have occurred. Local residents on California’s north coast have noticed an alarming decline in the once prolific kelp that is dependent on cold, nutrient rich waters for survival. Canopies that once covered much of the ocean’s surface have disappeared and the little kelp that remains is actively mowed down by a voracious grazer—the purple sea urchin. These areas that are overrun by sea urchins with hardly any kelp left are referred to as urchin barrens, a type of ecosystem largely devoid of the biodiversity that used to flourish there.

Photo © Neil Banas

Things started to drastically change in late 2013, when a mysterious disease wiped out a large portion of the local sea stars in Northern and Central California. As a result, purple urchin populations exploded in the absence of the sea star, their main predator. Then in 2014, abnormally warm waters hit the Northeast Pacific and persisted for the next couple years.  Often referred to as “the warm blob,” this large patch of warm water off the coast became the catalyst for a changing environment. Increased sea temperatures put immense stress on the kelp, slowing its growth, reproduction and causing damage to remaining fronds and tissue.  While warmer waters were taking their toll on the bull kelp forests, purple urchin populations were becoming more abundant and began to graze the kelp unchecked.

The appearance of warmer waters, a decline in sea stars, and an explosion of purple sea urchins is often referred to as the “perfect storm.” This extreme combination of stressors has decimated north coast kelp forests by over 90%.  Today, the seafloor looks more like an underwater desert dominated by sea urchins, with little else alive.

Local residents are concerned about what the future holds.  Marine ecosystems naturally alternate between kelp forests and urchin barrens, but rarely at such a large scale.  It usually takes a long time to shift back to a kelp-dominated ecosystem, and it is unlikely to naturally occur over the short term unless additional stressors are put on the urchin populations.

Dr. Cynthia Catton, a scientist for California Department of Fish and Wildlife (CDFW), said that while it is possible for a natural event to shift the balance of the ecosystem from urchin dominant towards kelp forest, there is much uncertainty revolving around when that might happen.

Alarmed by the drastic change in their local marine environment, outreach centers, management agencies, anglers and citizen scientists have joined forces in a community collaborative restoration program to address the issue instead of waiting for ecological unknowns.  Their strategy: harvest the purple sea urchins by hand in order to maintain a network of healthy kelp patches along the coast. Ultimately, the restoration program aims to provide materials to develop commercial uses of the purple urchins, ensuring long-term sustainable harvesting.


Currently, one of the primary drivers hindering kelp recovery is the purple urchin, a common sea urchin along the California coast that is able to survive in nutrient-low waters. Purple urchins feed mostly on algae like bull kelp, but eat many things, with beaks strong enough to chew on everything from barnacles to calcified algae. Along the north coast, urchins have focused their appetites on bull kelp, and they have since successfully outcompeted red urchins and abalone.


This “perfect storm” of natural events and the explosion of purple urchin populations have caused much duress for local fishermen who focus their efforts on red urchins and abalone.

  • The Recreational Abalone Fishery: Purple urchins have been outcompeting abalone for food and recent surveys show that abalone are retreating to shallower waters in search of food. Unfortunately, this puts abalone in the impact zone from storms and big waves that dislodge the abalone and throw them on shore, often breaking their shells.  Shutting down the recreational red abalone fishery hit Fort Bragg’s economy hard—and the closure has just been extended until 2021. Abalone fishing has been a long-standing tradition for a lot of families in California, and the loss of tourism associated with the red abalone fishery has not been replaced with an alternatively popular activity to help support the coastal town.
  • The Commercial Red Urchin Fishery: The highly-valued commercial red urchin fishery based out of Fort Bragg has seen a startling decline as red urchins suffer from a loss of kelp and the competition from purple urchins.  The market for red urchins is traditionally sushi based, and they are harvested for their reproductive tissue, called uni. Red urchins are typically larger than purple urchins and therefore provide more of the desirable uni. Unfortunately for the fishermen on the north coast, the persistent starvation conditions have resulted in significantly less uni production, reducing red urchin landings by more than 80% in recent years.

Catton expressed concern about other species that will be affected by the decline in bull kelp, such as rockfish: “We are seeing the impact to red urchins and red abalone right away…those are not subtle. But if we go too long without nursery habitat for rockfish species, we will be seeing those impacts as well,” she said.


For the past three years, Catton has been working with the commercial red urchin industry and local recreational fishermen to develop a program for harvesting purple urchins. This project examines whether or not human intervention can play a role in helping to shift the balance of the ecosystem back in favor of the kelp.

With CDFW leadership, a broad collaboration of community groups, scientists and resource managers (KELPRR) got together and hatched a plan to reduce grazing pressure in the kelp forest by harvesting the abundant purple urchins. The idea is that if there are fewer urchins in strategic locations along the coast, the kelp may have an opportunity to recover and replenish bull kelp spore availability more broadly. Catton of CDFW says one of the main purposes is to learn how we can best respond to the appearance of urchin barrens and help protect kelp forests that are declining in other areas as well.

Despite the long list of future unknowns, extensive amounts of time and energy have been put forth to save the kelp by KELPRR organizations including the Noyo Center for Marine Science, Watermen’s Alliance, CDFW and Reefcheck.

The KELPRR partners have selected three initial ‘kelp oasis’ sites along the northern California coast in which commercial urchin divers started harvesting purple urchins in 2018. These three sites—Caspar Cove, Noyo Harbor, and Albion Cove—used to have an abundance of kelp beds and are more sheltered from swells, making them more likely to contain kelp spores and support the regrowth of the kelp forests.

The Watermen’s Alliance, a union of recreational spearfishing clubs, is also organizing recreational harvest events at coordinated locations to further support the commercial urchin harvesting efforts.

Within the next year or two, the KELPRR partners will see if the efforts have been successful in reducing urchin grazing pressure enough to promote bull kelp growth.


Catton said that the experimental process of harvesting purple urchins is only occurring in zones outside of marine protected areas (MPAs): “Part of the strength of the MPA, is to see how the system responds without our manipulation.”

A long history of human activity in the ocean has often been associated with the demise of marine ecosystems, which is why marine protected areas were first established. Certain restrictions on human activity, such as no-take zones, in MPAs are designed to protect the natural ecology and support the diversity of life beneath the ocean—which typically classifies MPAs as healthier ecosystems due to this habitat protection.

However, Catton mentioned it is likely that geography has more to do with this ecosystem change than the lack of direct human impact, since it is such a complex environmentally driven issue.  In this case, “If the MPA happens to be at a river mouth, then that seems to be an area of more resilience. But that’s not due to the fact that it’s an MPA, it’s because [that area] is near a river mouth.”

In cases like this where warmer water and urchin grazing, not direct human activity, are recognized as drivers of the kelp loss, it becomes difficult to determine the degree to which humans should attempt to interfere, and whether recovery efforts will be successful.

Marine ecologist, Benjamin Ruttenberg, explains that there are other factors besides purple urchin predation that can limit kelp—so even with extensive urchin harvesting, a recovery of the kelp ecosystem might not happen. At best, it might work on a small scale but that would require continuous urchin harvesting and monitoring, Ruttenberg adds.

Since it is unknown whether human driven efforts will be able to save the kelp, MPAs will continue to act as important players for monitoring the ability of the natural ecosystem to respond to a changing marine environment, without human interference.

“I think that this is going to be a long-term issue that we are going to be grappling with,” Catton adds.

The future of kelp recovery in northern California remains uncertain, but the community restoration efforts give hope for saving the invaluable kelp that marine creatures and humans alike are so dependent on.

To get involved and stay up to date on the kelp recovery efforts please use the following links! There are many opportunities for involvement, whether you are a scuba diver, freediver, or just a concerned community member!

Relevant Articles