Artificial salt ponds are for the birds
Restoring the bay to 18th century conditions may threaten biodiversity
Ellie Cohen
Monday, June 10, 2002


GOVERNMENT AND NONPROFIT agencies are embarking on a sorely needed multimillion dollar effort to restore the San Francisco Bay estuary, including the significant purchase of 16,500 acres of artificial salt ponds in the South Bay, to protect wildlife, to enhance water quality and to sustain this remarkable ecosystem for generations to come.

However, to ensure the greatest biodiversity bang for each conservation buck invested, the public should be aware of a new restoration paradigm: Maintaining (man-made) habitat and restoring "natural" historic habitat are both critical to protecting wildlife and ecosystems.

The commonly repeated notion that most of the South Bay shoreline will be returned to 18th century conditions is at best naive and at worst, a threat to biodiversity.

Why? Restoring South Bay salt ponds exclusively to historic habitat may actually cause a loss in numbers of birds and a decrease in diversity of bird species.

Biologists from PRBO Conservation Science (founded as Point Reyes Bird Observatory in 1965) estimate that more than half a million shorebirds -- sandpipers and plovers -- use these salt ponds during spring migration alone.

Waterfowl -- ducks and geese -- make significant use of the salt ponds as well. Some shorebirds depend on the salt ponds for breeding, including about one-tenth of the remaining threatened western snowy plovers and the largest breeding populations of black-necked stilts and American avocets on the West Coast.

All told, PRBO's collaborative research in the South Bay has documented some 70 species of shorebirds and waterfowl feeding and roosting in salt ponds.

Extensive bird use of man-made salt ponds, and the ability of species to adapt to future environmental changes (such as continued development and global warming), point to the need to restore and manage for a mosaic of tidal habitats -- natural and artificial.

Why does this represent a new paradigm in our conservation thinking?

At one time, many of us, myself included, believed that the best way to protect wildlife was to "return to nature" (whatever that might mean). We now know, however, that some wild species flourish today because their survival and breeding needs are met by human altered habitat.

Fortunately, under the restoration plan developed by government and nonprofit agencies, about 40 percent of the South Bay salt ponds will be maintained and managed for shorebirds and waterfowl.

The remaining ponds will be converted to tidal marsh; 85 percent of this vital habitat has been lost. Restoration will attempt to incorporate all the features of historic marsh, and more. Because there is relatively little acreage, scientists will help ensure that today's restoration efforts address the needs of the widest range of species.

The bottom line is: To preserve biological diversity we no longer have the luxury to focus solely on restoring habitat to its "natural" state. Sound science is fundamental to understanding the complexities of the bay ecosystem as it functions today, and to our collective hope of sustaining biodiversity well into the future.

To find out more

Preserving some of the salt ponds is supported by two recent publications: "Turning Salt Into Environmental Gold" ( and "South Bay Salt Pond Restoration Feasibility Analysis (, and the San Francisco Bay Joint Venture. The venture is a partnership of 27 government agencies and nonprofits working to preserve and enhance the bay ecosystem. Its recommendations were guided by the 1999 Baylands Ecosystem Habitat Goals report, compiled over several years through the joint efforts of nearly 100 scientists.

Ellie M. Cohen is executive director of PRBO Conservation Science, founded in 1965 as Point Reyes Bird Observatory ( and serves on the Board of the San Francisco Bay Joint Venture (

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