As acidification threatens shellfish along North America’s Pacific Coast, Indigenous sea gardens offer solutions.
It’s low tide in Bodega Bay, north of San Francisco, California, and Hannah Hensel is squishing through thick mud, on the hunt for clams. The hinged mollusks are everywhere, burrowed into the sediment, filtering seawater to feed on plankton. But Hensel isn’t looking for living bivalves—she’s searching the mudflat for the shells of dead clams.
“I did lose a boot or two,” she recalls. “You can get sunk into it pretty deep.”
Hensel, a doctoral candidate at the University of California, Davis, is studying shells, which are composed of acid-buffering calcium carbonate, as a tool that could one day help shelled species survive in the world’s rapidly acidifying oceans.
The inspiration for Hensel’s research comes from Indigenous sea gardening practices. On beaches from Alaska to Washington State, First Nations and tribal communities built rock-walled terraces in the intertidal zone to bolster populations of shellfish and other invertebrates. Although these sea gardens have not been documented farther south, clams were also vital sustenance in central California. Coast Miwok and Southern Pomo people harvested clams for food and shaped shells into bead money, says Tsim Schneider, an archaeologist at the University of California, Santa Cruz, and a member of the Federated Indians of Graton Rancheria. “So taking care of your clam beds was actually kind of protecting your vault, your bank,” says Schneider…