At MCL’s June Climate Action Working Group meeting, Dr. Lydia Smith Vaughn of the San Francisco Estuary Institute described a growing area of climate science that is easy to overlook because so much of it happens below the surface.
The topic was blue carbon, the carbon stored and exchanged in coastal ecosystems shaped by the tides. In tidal marshes, seagrass meadows, and mudflats, carbon is captured by plants and stored in wetland sediments, often underground and out of sight. Vaughn explained that these ecosystems can hold significant amounts of carbon and, in some cases, sequester it at higher rates per acre than mature forests.
But the value of blue carbon is not as simple as counting how much carbon a marsh can store. Wetlands are dynamic systems, shaped by the constant interaction of sediment, plants, water, and rising seas. Scientists study those exchanges by reading the marsh from multiple angles, from the sediment below the surface to the vegetation above it, then using models to understand how these systems function over time.
California has begun incorporating blue carbon into climate planning, supported by improved mapping and new datasets that help track wetland conditions and estimate carbon storage. In San Francisco Bay, Vaughn noted, researchers are working with an unusually rich base of information, including monitoring of marsh elevation, vegetation change, and the transition zones where wetlands meet uplands.
For Marin, the discussion pointed to both the promise and complexity of coastal wetland protection. Marshes can help store carbon, but they also depend on sediment, space to migrate, and functioning tidal processes as sea levels rise. Restoration and shoreline adaptation projects must therefore weigh carbon benefits against the broader question of how wetlands can remain healthy and resilient as flooding, erosion, and sea level rise reshape the coast.
Vaughn emphasized that blue carbon may often be best understood as a co-benefit of wetland conservation rather than the sole reason for restoration. That distinction is important. Wetlands matter not only because they store carbon, but because they support habitat, buffer shorelines, and help communities adapt to a changing climate.
As Marin plans for sea level rise and the future of its bay and coastal habitats, blue carbon adds another layer to the case for protecting and restoring wetlands. Much of the work happens quietly, in mud, roots, and sediment, but its implications reach far beyond the shoreline.