How Are California’s Sea Otters Helping to Stop Erosion?

The sea otter population was decimated by the fur trade in the 18th and 19th centuries. Nearly hunted to extinction, these marine mammals numbered less than 2,000 by the early 1900s.

Thankfully, the future for sea otters is looking brighter due to conservation efforts like the Marine Mammal Protection Act and the Endangered Species Act. Their population is growing, and they are recolonizing some of their former habitats, with positive effects for entire ecosystems.

As predators, sea otters have a crucial role to play in keeping other animal populations in check. Sea otters enjoy eating crabs and urchins, yet their limited numbers meant that these invertebrates were becoming more numerous, with potentially disastrous environmental consequences. In the salt marshes surrounding Monterey Bay in California, burrowing crabs, a popular source of prey for sea otters, were chewing through marsh grass roots and burrowing into the ground, worsening erosion. There were even fears that some of the banks in the Elkhorn Slough estuary could collapse.

Sea otters have been back in Elkhorn Slough since the 1980s, and with their population growth and predation on crabs, erosion appears to have slowed. To examine this connection more closely, researchers surveyed numerous creeks in Elkhorn Slough and found a clear link between higher otter populations and less erosion, which has reduced from 30 centimeters to 10 centimeters per year. They also tested their hypothesis by fencing off some areas where sea otters couldn’t get to crabs. Not surprisingly, there was no slowing of erosion in those areas.

However, although the return of sea otters is widely recognized as a cause for celebration, most ecologists agree that it’s not a long-term solution to the problem of erosion, which is exacerbated by pollution, hydrology changes, and rising sea levels.

Saving more than sea otters: