A murky estuary once written off as an ecological disaster is now one of California’s most surprising Conservation success stories—thanks to sea otters.
As reported by Discover Wildlife, Elkhorn Slough, a coastal wetland just off Monterey Bay, was suffocating under decades of agricultural runoff.
Fertilizer-rich water from nearby farms turned the estuary into a soup of algae, killing off the vital seagrass meadows that Support more than 300 bird species and countless marine creatures.
Nothing worked—until the otters came back.
Sea otters, once hunted to near extinction, began repopulating the slough in the 1980s. What scientists thought was a quirky relocation turned out to be transformative. These small, voracious predators don’t just float on their backs looking cute—they eat. A lot. And crucially, they eat crabs.
Crabs in the slough had exploded in number, devouring the tiny grazers like sea slugs that normally keep algae in check. By munching on crabs, otters unwittingly unleashed a chain reaction: fewer crabs meant more grazers, which meant less algae, which meant healthier, thriving seagrass. That’s what scientists call a trophic cascade—and it worked beautifully.
Research led by Brent Hughes at Sonoma State University and Kathryn Beheshti proved that otters were key to stabilizing the slough. Areas where otters were excluded saw collapsing banks and withering seagrass. Where otters were free to roam, the ecosystem bounced back.
Today, Elkhorn Slough boasts California’s densest sea otter population. Yet threats persist—Pollution hasn’t gone away, and the otters need help to expand into other degraded estuaries. Recovery is possible, but it won’t happen without protecting predator species and curbing harmful agricultural practices.
Let’s use this success as a rallying cry. Support habitat protections, fight for cleaner water, and protect species like sea otters who do the hard work of keeping ecosystems in balance—naturally.
This article by Nicholas Vincent was first published by One Green Planet on 23 July 2025. Lead Image Credit :Wirestock Creators/Shutterstock.
Wildlife in catastrophic decline
The 73% decline in vertebrate wildlife populations during the last 50 years (mammals, birds, amphibians, reptiles and fish), is primarily driven by human activities that threaten biodiversity.
Habitat Loss and Degradation – human activities like deforestation, urbanization, and agriculture have led to the destruction and fragmentation of natural habitats, reducing the space and resources available for wildlife.
Pollution – air, water, and soil pollution from industrial activities, agriculture, and other sources can harm wildlife directly or indirectly by affecting their habitats and food sources.
Climate Change – changing weather patterns, rising temperatures, and sea levels are disrupting ecosystems and impacting species’ ability to adapt and survive.
Overexploitation of Resources – unsustainable hunting, fishing, and logging practices can lead to the depletion of populations and the loss of biodiversity.
Invasive Species – the introduction of non-native species can disrupt ecosystems, compete with native species, and threaten their survival.
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