Sea otters might save west coast kelp forests from total collapse–BUT THERE’s a catch

by Angela Zhang

For the past decade, an underwater drama has been unfolding in the golden, pacific waters of the Western United States. 

The plot features three pivotal characters with dynamic storylines: “The Blob” – a colossal ocean heatwave that has returned year after year– “zombie” sea urchins and the heroic return of the sea otters.

The Kelp Crash

In 2014, an ocean heatwave appropriately named “The Blob” for its persistent and mysterious nature hit the coasts of California, Canada and Alaska. Warm waters lasting from 2014 to 2016 and in combination with an El Niño event, contributed to a crash in kelp forest cover.

heat map of

COURTESY OF NOAA FISHERIES.

The year prior, the sea star wasting epidemic almost entirely wiped out Sunflower sea stars leading to an increase in their prey and the development of voracious, sea urchin populations. 

The virtual annihilation of the sunflower star was enough to allow kelp-decimating purple urchin populations to boom. As kelp became more scarce, purple urchins came out of hiding. In some areas, urchins covered the seafloor in a purple blanket while kelp canopies were reduced to almost nothing.

A cluster of purple urchins in an urchin barren

A cluster of purple urchins in an urchin barren. COURTESY OF WIKIMEDIA COMMONS.

While this new ecosystem–termed urchin barrens–may seem transitional, a shift in behavior has allowed high urchin populations to persist despite sparse kelp growths. These “Zombie” urchins remain in a vegetative state when they’ve consumed most of the available kelp allowing them to survive for large amounts of time with no sustenance. 

For now, plains of urchin barrens crowding coasts once lush with kelp forests stifle a hopeful recovery. 

In combination, “The Blob” and the largest documented epizootic contributed to a 95% crash in total kelp populations.

Images in 2008 (left) and 2019 (right) reveal losses in underwater kelp forest cover (yellow) along the California coast.

Images in 2008 (left) and 2019 (right) reveal losses in underwater kelp forest cover (yellow) along the California coast. COURTESY OF MEREDITH MCPHERSON.

Why kelp matters

A natural question to ask now is why does all this matter? Beyond the occasional sushi roll or seaweed snack, how does kelp actually affect us? 

While kelp is commonly used in many Asiatic cuisines and of cultural importance for tribes in the pacific northwest, most people are unaware of the ways in which kelp forests influence the fish they eat and the air they breathe

Kelp forests are also vitally important to coastal ecosystems and support a diverse spread of native fish and shellfish. Fish are often attracted to kelp forests by the abundance of edible organisms that live on and around kelp as well as the nutrients provided by the dense stalks of kelp. 

“They are a center for biological diversity that rivals coral reefs or tropical rainforests. Hundreds of species of fish depend on kelp forests and many hundreds of invertebrates also depend on kelp forests,” said Dr. David Wooding, Marine Biologist with the National Oceanic and Atmospheric Administration’s Restoration Center.

Beyond the role of kelp as an oxygen provider, the fast-growing seaweeds are also responsible for deep-sea sequestration of carbon.

The situation has been dire for a while now, but studies show that in some regions urchin ravaging has been mitigated by an unlikely hero. 

An unlikely hero: Sea Otters 

The sea otter, like kelp, was once ubiquitous in Alaska, British Columbia and along the south-western coast from Baja to Northern California. However, extensive fur trading in the 18th and 19th century hunted sea otters to extinction and they never quite recovered in some areas. 

Despite this, the presence of our underdog in Monterey Bay has resulted in the recovery of kelp in areas with remnant forests.  

“What this actually means is that otters are so important for this ecosystem because they are maintaining these remnant patches of kelp forests,” said Joshua Smith, a Ph.D. candidate and kelp researcher at UC Santa Cruz. “And those patches of kelp are the ultimate source populations to help replenish those barren patches.”

Sea otter eating a purple sea urchin

A sea otter eating a purple sea urchin. COURTESY OF MATT KNOTH.

The journey of the sea otter from near extinction to saving battered kelp forests may be harrowing, but like any groundbreaking solution, the reintroduction of sea otters comes with caveats.

The catch when it comes to Sea Otters

In British Columbia (BC), human-intervention led to a resurgence of sea otters that have consumed shellfish and exposed abalone to scarcity as well as preyed on our current target species: sea urchins. Reintroduction of sea otters has also been proposed in areas of Northern California where natural resurgence has not been observed.

Where otters have been reintroduced in BC and Alaska, our furry protagonist is affecting First Nations peoples’ access to food sources as well as local fisheries that depend on abundant sea otter prey. 

In many ways, managing the recovery of kelp forests depends on humans more than on otters or any other species. Reintroduction is a human intervention and the results will come to affect multiple species and all people that depend on the productivity of affected coastal ecosystems. 

Coastal Voices, a group of different indigenous leaders, scientists, and artists from British Columbia and Alaska, is facilitating discussions and planning around the impacts of reintroducing sea otters. 

“We should have a say in how we manage things. We live here, you know, they’re part of our lives. We know them,” said Walter Meganack Jr., chairman of the Port Graham Village Corporation and a member of Coastal Voices. “They are part of our resources that we made sure that were put to good use.”

Anne Saloman, a professor at Simon Fraser University and researcher working with Coastal Voices studies the effects of sea otters on kelp forests and coastal communities.

“The relationships between people, kelp forests, and sea otters have literally spanned millennia. And there were actually governance practices in place that managed these relationships, but the fur trade, it changed all that. Not only did it cause the elimination of sea otters but it caused an increase in their prey” said Salomon. 

Salomon emphasizes that systems and livelihoods that have become dependent on abundant sea otter prey–sea urchins, abalone, and lobster–will be affected by their reintroduction. As such, it’s vitally important that not only scientists, but local businesses and indigenous leaders are involved in the decision making process. 

“Our ancestors had a way of managing our relationship with the sea otters, they had a place in the ecosystem. With today’s laws there is a delicate balance and Indigenous people need to be a part of the discussion regarding their management,” said Skil Hiilans, Allan Davidson, Hereditary Chief

Are there other cases where you’ve seen conservation scientists, indigenous people and local communities work together on land stewardship? Let us know your thoughts in the comments. 

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Dilan Patel
Dilan Patel
1 month ago

People underestimate the amount of carbon sequestration kelp forests can have. Hopefully, we can revive these forests for the sake of our planet.

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