Hungry sea otters help save California swamps from erosion


WASHINGTON (AP) — The return of sea ​​otters and their voracious appetite helped save some of California’s swamps, according to a new study.

Sea otters are constantly eating, and one of their favorite snacks is striped crabs. These crabs dig burrows and also munch on the roots of swamp gherkins that hold dirt in place.

If left unchecked, crabs turn marsh banks “into Swiss cheese,” which can collapse in big waves or storms, said Brent Hughes, a marine ecologist at Sonoma State University. and co-author of the new study published Wednesday. in the journal Nature.

Researchers found that the return of crab-eating sea otters to a tidal estuary near Monterey, California, helped curb erosion.

“They don’t completely reverse erosion, but they slow it down to natural levels,” Hughes said.

For many years there were no sea otters in Elkhorn Slough.

The fur trade in the 19th century decimated their global population which once stretched from Alaska to California, Russia and Japan. At one point, there were only 2,000 animals left, mostly in Alaska.

Hunting bans and habitat restoration efforts have helped sea otters regain some of their former range. The first repatriates were spotted in Elkhorn Slough in 1984. The Monterey Bay Aquarium’s program to raise and release orphaned sea otters also increased the estuary’s population.

For the new study, researchers analyzed historical erosion rates dating back to the 1930s to assess the impact of returning sea otters. They also installed fenced areas to keep otters away from certain sections of streams for three years – these stream banks eroded much more quickly.

Previous studies of the return of large predators to various habitats – most famously the reintroduction of gray wolves to Yellowstone National Park – show how these species maintain ecosystem stability. Wolves reduced the number of elk and moose that fed on young trees and slowed the erosion of river banks.

Many previous studies relied on observations, but the design of the latest research left no doubt about the impact of sea otters, said Johan Eklöf, a marine biologist at Stockholm University who was not involved in the new study.

Other research has shown that sea ​​otters help kelp forests grow back by controlling the number of sea urchins that munch on the kelp.

Sea otters “are incredible discoverers and eaters,” said Brian Silliman, a coastal ecologist at Duke University and co-author of the latest study.


The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Education Media Group. The AP is solely responsible for all content.


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