Rising Tides Drive a Bay Area Push to Bring Back Vanished Marshlands

The Bay Area is more than halfway toward its goal of restoring 100,000 acres of tidal wetlands, which are a natural buffer to floodwaters from future sea level rise.

The Wetlands Regional Monitoring Program published data in September showing that restored tidal marshes nearly quadrupled from 2000 to 2020. On Tuesday, at the State of the San Francisco Estuary Conference, scientists announced that several thousand acres would be added through 2024. The Bay Area now boasts 57,800 acres of restored tidal marsh.

“That’s really tremendous progress, especially compared to other areas of the country or other areas globally where we’re seeing wetland loss,” said April Robinson, a senior scientist with the San Francisco Estuary Institute.

Historically, more than 190,000 acres of tidal wetlands — marshes that flood during high tides — existed across the Bay Area. But as people developed the region in the 19th and 20th centuries, more than 80% of the marshes were destroyed.

Bay Area voters approved Measure AA in 2016, establishing a $12-per-year parcel tax meant to generate around $500 million over two decades. The tax is meant to fund habitat restoration, such as rebuilding wetlands. Robinson credited that measure, in part, with the region’s success.

Bay water could rise by 1 foot by 2050 and more than 6 feet by the end of the century. The growing number of wetlands along the bay’s rim is just one factor in how well prepared the region is for rising seas as a result of human-caused climate change.

“There is a worry that we will start to lose marshes to sea level rise,” Robinson said. “Because marshes have that capacity to deal with sea level rise, the more that we can get those restoration projects established before sea level rise rates increase, the better shape we’ll be in to have our marshes persist.”

Scientists from multiple organizations are evaluating the health of the region’s remaining wetlands, like the Dotson Family Marsh on the edge of the city of Richmond.

The East Bay Regional Park District spent $14 million in public and private funds to restore the 150-acre marsh, which sits inside the Point Pinole Regional Shoreline, back in 2017.

Earlier this month, Sarah Pearce, a geomorphologist and a wetland scientist at the San Francisco Estuary Institute, led her team tromping through the mud at the marsh on a research trip. They examined the birds flying overhead, the algae growing below, the tides and a variety of plant life.

Pearce’s team scored the marsh 66 out of 100, which she said is a “fair condition” and expected for a young marsh. The tide flows in and out of the area well, which boosted the score. As seas rise, tidal wetlands can migrate upland, so long as they have the space to do so. For now, the marsh can grow upland but will eventually hit a railway, homes and businesses.

“That’s really important when we think ahead because with sea level rise, the marshes need someplace to go,” Pearce said. “I’m convinced that as it ages, it will keep growing and increasing in complexity and get better and better.”

There are other worries, including whether enough sediment is left in the bay to rebuild marshes.

Pearce said most of the Bay Area’s marshes are in fair condition, but the Whittell Marsh, located just a few miles north, is in much better condition.

Christina Toms, an ecological engineer with the San Francisco Bay Regional Water Quality Control Board, considers the marsh on the north-eastern edge of Point Pinole Regional Shoreline a “benchmark” for how “wetlands historically throughout the estuary used to function.”

Bricks and sea glass strewn across the beach remind visitors that the park was used for dynamite manufacturing for nearly 80 years. But the marsh remains.

Within a thousand feet of the water’s edge, visitors can find mudflats, beach, tidal marsh and rolling grasslands. Toms said it’s what the Bay Area’s wetlands looked like before people developed the region and destroyed many of them.

“Here we’re connected to uplands, we’re connected to this beach, and all the pieces work together,” Toms said. “This marsh can help inspire designers and planners to think about how they can create systems that are similar to this.”

Toms wants to restore as much Bay Area marsh habitat as possible for wildlife and people.

“I want my kid to be able to go anywhere in the San Francisco Bay Area and see a thriving tidal marsh, hear a Ridgway’s rail calling from a channel, and see shorebirds foraging along a coarse beach,” Toms said. “That’s my dream.”