The second ingredient in wetlands restoration is dirt - plenty of it. Before it became Silicon Valley, the area around the South Bay was an agricultural zone known as "The Valley of Heart's Delight." Farmers pumped out groundwater for decades to irrigate fruit and nut trees, lowering water tables. Some pond bottoms sank by as much as 13 feet, too far below the water line to support marsh plants.

To start recreating marshes, workers will breach the dikes so that waves can carry in fresh sediment. In 10 to 15 years, when enough sediment has piled up, cordgrass and pickleweed will start to colonize the mud flats. Eventually the plants will thicken into habitat for species like the endangered California clapper rail and salt marsh harvest mouse. 

But because the project covers such a big area, breaching ponds could interfere with larger processes in the Bay. "We know a lot about tidal marsh restoration, but there are questions that stem from the ecosystem scale of this project," says Trulio. For example, opening up the salt ponds could draw sediments from existing mud flats farther north in the Bay that provide crucial foraging areas for migrating water birds. "Losing all the mud flats and not gaining any marsh is everybody's nightmare," says executive project manager Steve Ritchie of the California State Coastal Conservancy. "We're pretty confident that we know how sediment moves in the Bay, but we're going to go slowly on opening up the southern ponds." 

Mercury is also a concern. For over a century, mercury deposits from the New Almaden mines near San Jose and other sources have washed into the Bay, and stronger tidal circulation could stir them up. Bacteria found in wetlands can convert mercury to toxic methylmercury, the form that moves up through food chains. And high mercury levels have already been found in clapper rail and tern eggs in the area. 

Yet another uncertainty is whether invasive species will move into new marshes. Many non-native species are present in the Bay, notably spartina altiflora, a non-native cordgrass that was planted several decades ago to stabilize shorelines. Here as well as in Washington's Puget Sound, spartina is displacing native grasses and reducing water circulation despite energetic weeding by hundreds of volunteers. Breaching ponds may also displace existing colonies of California gulls. These large, aggressive birds prey on smaller species like snowy plovers and may compete with them for space on the remaining managed ponds. 

Restoration agencies plan to tackle these uncertainties through adaptive management, an approach that uses careful trials - such as breaching specific ponds or moving dikes - to determine which actions succeed or fail. Results from one step will help scientists decide what to do next, and ultimately will determine what fraction of the salt ponds are converted back to marshes. Phase I of the project will restore about 1,500 acres of tidal habitat between 2008 and 2010. 

 

All told, the salt-pond restoration is projected to cost nearly $1 billion over 50 years. A dozen other, smaller wetland restoration projects covering more than 23,000 acres are planned or under way around the Bay. Save the Bay estimates that all of these projects could be completed for a total of $1.43 billion, of which about $370 million has already been invested. 

What's needed now is a cohesive strategy to raise the balance from federal, state and local sources and target the projects that are the most scientifically sound. A 2006 survey of Bay Area residents found that about 80 percent were willing to pay $10 yearly in taxes or fees to improve the Bay. Save the Bay would like to see managers tap this goodwill through local funding measures rather than looking to Congress for most of the money. "Often politicians are behind the curve on how willing the public is to pay for environmental benefits," says Lewis. The funding process is especially complicated in San Francisco because nine counties and dozens of towns adjoin the Bay, and each has different concerns about flooding, infrastructure, land conservation and other issues. 

California has lost at least 90 percent of its wetlands, more than other West Coast states, but development and pollution are also stressing important estuaries like the lower Columbia River in Oregon and Puget Sound. Water diversion projects have reduced river flows into these bodies, causing saltwater intrusion that changes the estuaries' chemistry and destroys fish habitat. And growth in areas like King County, Wash., and coastal Oregon creates constant pressure to dredge or fill in wetlands for other uses. 

"Wetlands are inconvenient. If we want to build a road from point A to point B and there's a wetland in the way, it will always lose," says Robin Clark, habitat restoration manager at People for Puget Sound. 

If local agencies find a way to meld their budgets and agendas, the salt pond project could energize similar efforts to restore other West Coast wetlands. "Hopefully, we can show that even with multiple jurisdictions, you can take a regional approach and find ways of collaborating," Lewis says. "Political boundaries have to recognize ecological boundaries. If the West had been required to develop based on watersheds and water realities, instead of artificial political lines and invented water boundaries, growth patterns would have been very different from what we see today."

 

Jennifer Weeks is a freelance environmental writer based in Watertown, Massachusetts. 

This article was made possible with support from the William C. Kenney Watershed Protection Foundation and the Jay Kenney Foundation.