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Hungry Sea Otters Are Saving California's Marshland from Erosion, Study Finds

The return of sea otters and their voracious appetites has helped rescue a section of California marshland, a new study shows.

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A recent study reveals that the resurgence of sea otters and their insatiable appetites has played a crucial role in saving a portion of California marshland.

Sea otters are known for their constant eating habits, with a particular fondness for the striped shore crab. These crabs, by digging burrows and nibbling on the roots of marsh grass pickleweed, contribute to the destabilization of the soil in the marsh banks.

According to Brent Hughes, a marine ecologist from Sonoma State University and co-author of the study published in the journal Nature, if left unchecked, these crabs transform the marsh banks into something resembling "Swiss cheese," making them susceptible to collapse during storms or heavy waves.

The research focused on a tidal estuary near Monterey, California, where the return of sea otters that prey on these crabs helped mitigate erosion. Although they don't completely reverse the erosion, the sea otters slow it down to natural levels, as explained by Hughes.

Sea otters were absent from Elkhorn Slough for many years due to the devastating impact of the 19th-century fur trade, which significantly reduced their global population. Hunting bans and habitat restoration efforts gradually allowed sea otters to reclaim some of their former territory. The first sightings in Elkhorn Slough occurred in 1984, and the Monterey Bay Aquarium's program for raising and releasing orphaned sea otters further contributed to the estuary's population growth.

To assess the impact of sea otters' return, researchers analyzed historical erosion rates dating back to the 1930s. Additionally, they conducted experiments by setting up fenced areas to prevent otters from accessing certain creek sections for three years, observing faster erosion in those areas.

The study's design left no room for doubt regarding the sea otters' impact, according to Johan Eklöf, a marine biologist from Stockholm University not involved in the research. Previous studies, such as the reintroduction of gray wolves to Yellowstone National Park, have highlighted how the return of top predators can maintain ecosystem stability by regulating prey populations.

Sea otters have also been credited with aiding kelp forest regrowth by controlling the population of sea urchins that feed on kelp, further showcasing their remarkable role in ecosystem management, as noted by Brian Silliman, a coastal ecologist from Duke University and co-author of the study.