Sea otters are making a comeback in California — and they’re curbing erosion

For decades, the number of California sea otters cratered. But they’ve been making a comeback — and are helping curb erosion along the coast by eating the crabs that accelerate it.

ARI SHAPIRO, HOST:

For decades, the number of California sea otters cratered, but since the 1980s, they’ve made a stunning comeback, a return that researchers now say helped restore their coastal habitat. Here’s science reporter Ari Daniel.

ARI DANIEL, BYLINE: For years, Elkhorn Slough in Monterey Bay, Calif., was falling apart.

BRENT HUGHES: They opened up a new harbor in the 1940s, and so all this new tidal energy was eroding away the marshes.

DANIEL: Brent Hughes is a marine ecologist at Sonoma State University. Plus, he says there was sea level rise and an explosion of shore crabs.

HUGHES: They burrow. On top of it, they eat the roots. What this all does is destabilizes the banks, the shoreline, and it just causes this erosion.

DANIEL: The marsh was disintegrating, making the coastline and people living there more vulnerable to flooding and storm surge. And there was just no way of getting it back without an expensive intervention. But Hughes knew those shore crabs would be an all-you-can-eat buffet for sea otters.

HUGHES: They’re really good at eating crab, and it’s just easy pickings for them. They just eat them like popcorn – shell and all.

DANIEL: For a long while, though, sea otters were teetering on the edge of extinction, killed by the hundreds of thousands for their pelts, which over time let the shore crabs get the run of the place. But a small group of several dozen otters managed to survive near Big Sur and by the 1980s, with a bit of human help, began to recolonize the coastline. Today, Elkhorn Slough has the highest concentration of otters in all of California, about 100 in total.

HUGHES: Meaning the hotel is full – you can’t stick one more otter in there if you tried.

DANIEL: So Hughes wondered, might the return of all these…