Restoring Salt Ponds Back to Marsh

Government agencies working with environmental nonprofits reached a historic moment this week near Alviso to bring back the marsh habitat from old salt ponds—and ultimately improve the ecosystem of the San Francisco Bay.

An excavator cut a notch in the levee that separated a dry salt pond from the southern tip of the Bay, allowing water to flow into the 330 acres, according to Doug Cordell, a spokesman with the U.S. Fish and Wildlife Service, the agency that owns and manages the land.

The dry salt pond, on the Alviso side of the Don Edwards San Francisco Bay National Wildlife Refuge, known as A6, is just one piece of the South Bay Salt Pond Restoration Project, the largest tidal-restoration project on the West Coast.

"One of the wonderful things about this kind of restoration is that a lot of it will happen by itself," said David Lewis, executive director of Save the Bay, a nonprofit partner of the project.

Pickleweed and cordgrass seeds are in the adjacent marshes, he said. As bay water brings seeds, along with sediment and mud, a lot of the vegetation should re-establish itself in the first year.

"We've seen that in the other ponds," he said, which was faster than what scientists involved in the project had predicted.

The land was privately held by Cargill Inc. as salt-evaporation ponds, some of which date as far back as 150 years. Public agencies and trusts purchased about 15,100 acres less than a decade ago and set to work on the restoration project.

"Communities like Milpitas and Mountain View, for decades, have been walled off from the Bay," said Lewis. The salt ponds are areas that were once part of a tidally active Bay, he said, where communities were connected by waterfronts and other points of access.

Restoring the area to its natural marsh habitat has other benefits, such as flood control, said Lewis, particularly in Alviso where areas are below sea level.

'They work like a sponge," he said. Marshes can soak up a lot of water and release it slowly; whereas, wave energy can erode levees, marshes reduce wave energy.

"They work hand in hand," said Cordell, about levees and marshes. "With climate change and a rise in sea level, marshes will reduce the size of the levees needed,  making them cheaper to build and maintain."

But restoring the dry salt pond known as A6 has created its own challenges.

Since the '80s, a colony of California gulls that have adapted and made the dry salt pond into a breeding ground will have to find a new home—all 23,000 of them.

The Milpitas-based San Francisco Bay Bird Observatory has monitored the colony for the last three decades. The birds are problematic, because they will be "out and about looking for new habitat," said Jill Demers, executive director. 

Breeding season for the California gulls is in April or early May.

"There's a lot of potential for conflict here," she said, one of which is if the gulls choose to relocate to Pond SF2 (see map), a highly engineered and expensive bird habitat on the west end of the Dumbarton Bridge.

The gulls don't mix well with other birds and have been known to eat the eggs and chicks of other threatened species, such as the Western snowy plover. To keep the gulls away from the habitats of these other birds, decoys, noises and active hazing techniques may be used, said Demers.

Working with the U.S. Fish and Wildlife Service, the SFBBO will help track the gulls through tagging and use of radio telemetry. 

"It's an issue that we're monitoring in order to protect threatened species," said Cordell. "It's a balancing act." 

While the A6 site is in a remote area not easily accessible to the public, there will be other restoration projects that, like Pond SF2, will be more visible. A16, just next to the environmental center, and the parcel just of north it, A17, are scheduled for work in the beginning of 2012.