California Sea Grant College Program

Sea levels in California, south of Cape Mendocino, are predicted to rise between 90 and 95 cm between 2000 and 2100, with a range as high as 167 cm and as low as 42 cm, according to a 2012 report by the National Academy of Sciences.

Whatever the ultimate rise in sea level is, it will largely control the fate of tidal marsh habitats in the San Francisco Bay-Delta.

Tidal marshes are wetlands periodically inundated by tidal flows and, unlike mudflats, are vegetated. They provide overwintering and foraging habitat for resident and migratory birds, and are a buffer against floods and storm surge. They also filter and remove pollutants.

Only about 5 to 10 percent of the delta’s historic tidal marshes remain. Most fringe an aging collection of levees. Former wetlands— now diked, behind levees and dry—are sinking and below sea level by as much as 20 m in some places.

Plans are underway to restore thousands of acres of tidal marshes. Whether these marshes are sustainable in the long term will be deter- mined by their ability to build elevation or migrate to higher ground.