How Sea Otters Can Help Save the Planet

As a keystone species, sea otters play a vital role in restoring marine ecosystems and strengthening our natural defenses against climate change—but they need your help. From rehabilitating sick and injured animals to a potential reintroduction to their historical range, learn about important conservation efforts to protect the threatened southern sea otter.  

What Makes the Sea Otter a Keystone Species? 

Beneath the ocean surface are giant forests teeming with life. Made up of rapidly growing large brown algae, kelp forests are one of the most biodiverse ecosystems on the planet—home in California to rockfish, red octopuses, purple sea urchins and hundreds more species of marine animals and plants.  

Within this ecosystem and at the top of its intricate food web are sea otters: guardians of the kelp forests. Sea otters are a keystone species, which means they are essential to maintaining a healthy ecosystem, and can even restore it. As top predators of invertebrates, sea otters dive to the ocean floor to forage for shelled creatures like urchins, crabs, clams and abalone. Unlike most marine mammals, they rely on a very rapid metabolism and extremely dense fur to stay warm in the chilly ocean. In fact, sea otters eat about a quarter of their body weight every day! 

The impact of a keystone species extends far beyond the animals they primarily prey upon, so how does a sea otter’s big appetite protect an entire kelp ecosystem? Purple sea urchins are voracious grazers that sweep across the ocean floor to feed on standing kelp. When sea otters munch on these small, spiky animals, they keep urchin populations low enough for kelp forests to flourish. 

Sea otters are also important to the health of seagrass meadows and salt marshes in estuaries, where a freshwater river or stream meets the ocean. As a keystone species in these ecosystems, sea otters mostly eat crabs. When sea otters are present to manage crab populations in seagrass meadows, snails and slugs that crabs like to eat can rebound. Healthy populations of snails and slugs then eat algae before it smothers the seagrass, allowing the underwater meadows to grow more efficiently and provide habitat to many species. 

Salt marshes are coastal wetlands that are regularly flooded and drained by ocean tides. Along a marsh’s shore banks, shore crabs burrow into the soil and eat plant roots, which can result in bank erosion and the loss of healthy marsh grasses. By managing populations of these destructive crabs in estuaries like Elkhorn Slough in Moss Landing, California, sea otters help stabilize the shore banks and allow the salt marshes to flourish. 

Protecting the Coast from the Effects of Climate Change 

Not only do sea otters support thriving marine ecosystems to provide critical habitat for themselves and other species, but they also strengthen our natural defenses against climate change. Kelp forests, seagrass meadows and salt marshes capture and absorb large amounts of carbon dioxide from the Earth’s atmosphere to grow their leafy underwater structures. This process, known as carbon sequestration, can be key to addressing the climate crisis as it pulls in excess carbon dioxide caused by burning fossil fuels like coal, oil and natural gas.  

When kelp forests, seagrass meadows and salt marshes can flourish, they help protect wildlife and humans from climate change’s impacts by mitigating sea level rise and buffering coastlines from extreme weather events. 

The Critical Need to Advance Ocean Health 

A keystone species is like the top stone of a rock arch—if this top stone is removed, the entire structure falls. So when sea otters are not present to eat urchins in kelp forests or crabs in estuaries, biodiverse environments can lose their balance and collapse. 

Along the Pacific Coast, where sea otters have disappeared from most of their historical range, many nearshore ecosystems are suffering. Seagrass meadows have experienced massive die-offs, leading to increased shoreline and estuary erosion, worsened by rising sea levels. And as urchin populations continue to multiply, kelp forests are being devoured and transformed into vast urchin barrens where very few marine species can survive. From ocean pollution to warming waters, harmful human activity is only further degrading these vital marine ecosystems. 

This wasn’t always the case. Sea otters used to live along the entire North Pacific Rim from Japan to Baja California, Mexico, coexisting with humans for thousands of years. But during the maritime fur trade in the eighteenth and nineteenth centuries, they were hunted extensively for their luxurious pelts. By the early 1900s, sea otters were on the brink of extinction. 

Sea otter populations around the world have increased thanks to conservation efforts, but in California there are still only about 3,000 individual sea otters, and population growth has stalled. The California population of southern sea otters is listed as a threatened species, and the survival of each individual otter is crucial to the future of this population. 

The Marine Mammal Center’s Work with Sea Otters 

The Marine Mammal Center is one of the few organizations permitted to rehabilitate southern sea otters. Our team of animal care and veterinary experts as well as volunteers provide state-of-the-art medical treatment to sick and injured sea otters with the goal of returning them back to the ocean. Thanks to support from caring people like you, many animals have gotten a second chance at life. 

Using knowledge gained from sea otter patients at our hospital in Sausalito, California, we have expanded our understanding of health threats they face, which informs how we can better protect this species. As part of our efforts to help southern sea otters recover, our research focuses on understanding diseases such as  domoic acid toxicity and toxoplasmosis that affect them, and developing treatments to help return them to their ocean home. 

Southern Sea Otter Coastal Range 

Today, in places where sea otter numbers have increased in California, kelp, seagrass and salt marsh ecosystems are also recovering and experiencing renewed productivity. 

Unfortunately, southern sea otters still only inhabit 13 percent of their historical range, from about Pigeon Point in San Mateo County to Point Conception in Santa Barbara County. Sea otters face threats like shark bites at the edges of their current range, where protective kelp cover is sparser, preventing them from traveling into their historical territories. Despite extensive conservation efforts protecting sea otters, the population has been unable to naturally expand its range for more than two decades. 

Given their small numbers and limited geographic range, southern sea otters are especially vulnerable to the risks of oil spills and infectious diseases. Catastrophic events like these could decimate the population. For this threatened species to truly recover, southern sea otters may need to return to the places they once lived.  

Reintroduction as a Conservation Tool 

To help address this problem, in 2022 the U.S. Fish and Wildlife Service (USFWS) studied the feasibility of sea otter reintroduction in Northern California and Oregon. Reintroduction is a conservation tool that helps a species expand its range by releasing animals into areas where they historically existed. USFWS found that not only is sea otter reintroduction biologically possible, but it may also expedite the recovery of this threatened species and restore vital kelp and seagrass ecosystems. 

From protecting marine biodiversity to fighting climate change, sea otter reintroduction could help more of the Pacific Coast benefit from the presence of this furry keystone species. Parallel to USFWS’s assessment, the Center is part of a collaborative network of conservation organizations, researchers, tribes, community leaders and other groups exploring the possibility of returning sea otters to Northern California and Oregon. This is critical to ensure that any reintroduction would be the most successful for sea otters, the environment, and the people who live and work in coastal communities. 

Together we are advancing the science necessary to decide whether and where to reintroduce this threatened species, as well as gathering key input from stakeholders—including people like you. You can make your voice heard about a potential sea otter reintroduction by taking Sea Otter Savvy’s We Were Here survey. 

Learn More 

From rehabilitating sick and injured animals to monitoring them in the wild, hear from the Center’s experts as they explore the intricacies of sea otter conservation and the potential reintroduction of this population back to their historical range. Watch now: Second Chances for Sea Otters