Sea Otters’ Homecoming Slows Erosion, Offers Hope For Coastal Ecosystems

The return of sea otters to a Californian estuary proves there is a positive “payoff” from conservation, say scientists.

The homecoming of the super cute marine mammals to their former habitat has slowed erosion of the area’s creekbanks and marsh edges by up to 90 percent, according to a groundbreaking study.

The resurgence of the charismatic predators in the saltmarsh-dominated Elkhorn Slough in Monterey County has sparked fresh hope among conservationists dedicated to improving the health of coastal ecosystems – and marks a “significant” success story.

Study co-author Associate Professor Christine Angelini said: “This is a solutions-oriented paper that tells us there are manageable actions we can take to produce positive results.

“In this instance, restoring the otter population was achievable without significant effort, and as a result, we are now unlocking several decades of benefits from that one act of conservation.”

The findings, published in the journal Nature, show that the erosion of creekbanks and marsh edges in areas with large sea otter populations has slowed, mainly because of the otters’ “insatiable” appetite for plant-eating marsh crabs.

The American researchers pointed out that the erosion rate has declined at a time when rising sea levels, elevated nutrients, and stronger tidal currents should be causing the opposite effect.

Study senior author Professor Brian Silliman, of Duke University’s Nicholas School of the Environment, said: “It would cost tens of millions of dollars for humans to rebuild these creekbanks and restore these marshes.

“The sea otters are stabilizing them for free in exchange for an all-you-can-eat crab feast.”

By documenting for the first time that reintroducing apex predators to their former habitat can bring stability to a collapsing ecosystem, the researchers raised the question of whether similar results could be achieved in ecosystems worldwide.

Lead author Dr. Brent Hughes, Associate Professor of Biology at Sonoma State University, said: “Reintroducing the sea otters didn’t reverse the losses, but it did slow them to a point that these systems could restabilize despite all the other pressures they are subject to.

“That suggests this could be a very effective and affordable new tool for our conservation toolkit.”

Angelini, director of the Centre for Coastal Solutions at the University of Florida, says it is an “encouraging” sign as she and her colleagues confront similar threats to the state’s coastlines from sea level rise, intense storms, and excess nutrients spilling into coastal waters.

She said: “All these challenges can feel unsurmountable.

“This study indicates to us that, if we truly understand the ecosystem and know what levers to pull, we can see significant benefits to the health and stability of these systems.”

To understand the impact the sea otters were having on the landscape, the research team conducted surveys across 13 tidal creeks, as well as field experiments at five locations along the estuary over a six-year period.

Otters were excluded from some test sites but allowed to recolonize others, using a caging system designed by Angelini.

She said: “As a graduate student in biology, I had been setting up these types of cages and manipulating access to predators and their prey in salt marshes all over the Southeastern US, so I had the skill set.

“I’ll never forget building all the cages in the parking lot of the estuary out in California.

“And all these years later, we now see these amazing results.”

Dr. Angelini added: “It’s an uplifting story about the benefits of conservation and persistent, long-term research.”

Produced in association with SWNS Talker