Against all odds, a distressed California coastal ecosystem is on the mend, in large part, thanks to the insatiable appetite sea otters have for crabs.

In a groundbreaking study published this week in Nature, scientists revealed that the return of sea otters to their former habitat in a Central California estuary has slowed erosion of the area’s marsh banks by up to 90%.

The resurgence of these charismatic marine mammals to the salt marshes of Elkhorn Slough in Monterey County sparks hope for improving coastal ecosystems and marks a significant ecological success story.

“It would cost tens of millions of dollars for humans to rebuild these creek banks and restore these marshes. The sea otters are stabilizing them for free, in exchange for an all-you-can-eat crab feast,” said senior author and marine conservation biology professor Brian Silliman.

Like many California estuaries, Elkhorn once was a foraging habitat for sea otters, which need to eat the equivalent of about 25% of their body weight every day—around 20 to 25 pounds of food, with crabs being one of their favorite meals.

But after fur traders hunted the local otter population nearly to extinction, the number of crabs exploded over the next century. Crabs eat salt marsh roots, dig into salt marsh soil, and over time can cause a salt marsh to erode and collapse.

“It’s an uplifting story about the benefits of conservation and persistent, long-term research.”