Bay Area wetland growth defies global trend

A new report from the Wetlands Regional Monitoring Program (WRMP) indicates that restored tidal wetlands in the Bay almost quadrupled from 2000 to 2020, bringing the total to 53,000 acres and growing.

The WRMP is sharing its “Tracking Tidal Wetland Extent in San Francisco Bay” report as part of National Estuaries Week (Sept. 20-27, 2025).

Using cutting-edge automated mapping for more accurate tracking of tidal wetland areas, as well as standards to measure future progress, the new report provides the first high-resolution update for the San Francisco Bay region’s tidal wetland area since 2009. Despite the importance of tidal wetlands, scientists previously struggled to precisely gauge the size of these areas.

“This systematic way of tracking our region’s wetland extent over time will show us where wetland restoration is succeeding and where it needs more support," explained Sasha Harris-Lovett, a WRMP program manager at the San Francisco Estuary Partnership, which co-manages the program with the San Francisco Estuary Institute. "This is vital information that lets us more effectively and efficiently restore more tidal wetlands around San Francisco Bay.”

Tidal wetlands are marshes that flood daily as the tides fill their mazes of channels and ponds. They protect shorelines, store carbon, filter water, and provide habitat. Restoration efforts are driving the increase in these ecosystems, which once dominated the shoreline in the North Bay and South Bay.

“These really unique wetlands were a big part of the Bay historically,” noted April Robinson, a senior scientist at the San Francisco Estuary Institute and an author of the new report. “They support plants and animals that we don't find anywhere else, they provide food for many different types of wildlife, and they provide protection for our shoreline in the face of sea level rise. They're areas where we can fish, recreate by the water, and connect to nature.”

After upwards of 80% of the region’s historic tidal wetlands were destroyed by 19th and 20th century development, Bay Area voters in 2016 approved Measure AA by a more than 70% to 30% margin. The measure, which established a $12 per year parcel tax, will generate some $500 million over 20 years to fund habitat restoration, enhancement and protection projects overseen by the San Francisco Bay Restoration Authority.
 

About the San Francisco Estuary Partnership: The San Francisco Estuary is named in the federal Clean Water Act as one of 28 “estuaries of national significance." Hosted by the Association of Bay Area Governments, the San Francisco Estuary Partnership for over 35 years has worked with local communities and with federal and state agencies to improve the health of California’s most urbanized estuary.