The 116,000-acre Suisun Marsh is the largest contiguous brackish water wetland in western North America, providing food and habitat for thousands of migratory birds on the Pacific Flyway and many species of plants, fish and wildlife.The marsh is where fresh water from the Sacramento-San Joaquin Delta mixes with salt water from San Francisco Bay.

Biodiversity

It is a complex of tidal wetlands, diked seasonal wetlands, sloughs and upland grassland that comprises more than 10 percent of the remaining wetlands in California.

The marsh is a center of significant biodiversity because of its continued protection and management as a wetland ecosystem. Most of the marsh is managed by the state and private duck clubs for hunting and wildlife conservation.

The diversity is reflected in the large array of plants and animals, especially native species, like the endangered salt marsh harvest mouse.  Some species, such as Suisun song sparrow and Suisun thistle are largely endemic to the marsh, according to the book, “Suisun Marsh, Ecological History and Possible Futures.”

Salinity Control

State Water Project and Central Valley Water Project exports from the south Delta reduce the Delta outflow to the ocean, which increases salinity. In the 1980s, project managers installed several salinity control gates in Suisun Marsh to protect the wildlife habitat. Plant growth, for instance, can be impaired, which in turn affects waterfowl that feed on the plants.

These gates are opened when water flowing out of the delta is fresh (generally in the winter) and are closed when the salt water creeps back up the Bay in the summer.

Challenges

Pelagic fish declines and scientific surveys of the Delta and Suisun Marsh in 2005 revealed an ongoing, sweeping population crash of native pelagic fish. The decline could not be explained by drought or any other easily identifiable cause.

The Bay Delta Conservation Plan is responsible for developing an in-Delta and Suisun Marsh habitat restoration program. The plan’s conservation efforts are in accordance with the federal and state Endangered Species Act and the state’s Natural Community Conservation Planning Act.