Along the Sonoma and Mendocino coast, where bull kelp forests collapsed by more than 90% after 2014, restoration is no longer just a hope: it’s a funded, running project. NOAA’s Office of Habitat Conservation, working with the Greater Farallones Association, Moss Landing Marine Laboratories and Sonoma State University, is putting a $4.9 million grant toward restoring kelp across three sites inside Greater Farallones National Marine Sanctuary, with a goal of bringing kelp back to as much as 27 acres of coastline.
The first step was clearing the purple sea urchins that have grazed the seafloor down to bare rock in these “urchin barrens.” Over several weeks in the fall, a commercial urchin diver hand-removed roughly 17,000 pounds of urchins from a site at Timber Cove, cutting local urchin density by about 90%. That gave researchers a clean slate to test three outplanting methods side by side: concrete blocks seeded with kelp spores, mesh bags packed with spore material, and juvenile kelp sporophytes anchored to the rock with twine.
Divers and researchers are now tracking which approach actually takes hold, using underwater buoy sensors and drone surveys to follow kelp growth, or die-back, through the following field season. If one method clearly outperforms the others, it could scale up to the sanctuary’s full 27-acre target, and offer a playbook for similar bull kelp collapses elsewhere on the West Coast.
Further reading: NOAA Fisheries, “Pioneering Project to Restore Bull Kelp Forests in Greater Farallones National Marine Sanctuary in California” (2024).