The Delta is an integral part of the largest estuary on the West Coast of the Americas and one of its most unique ecosystems, where fresh water from mountain runoff meets saltwater of the San Francisco Bay and Pacific Ocean. It connects rivers originating in the Sierra Nevada to San Francisco Bay and the Pacific Ocean and productive upland with tidal marsh. It is home to 55 fish species, 750 animal and plant species and other wildlife supported by 1,000 miles of waterways and habitat.
The Delta ecosystem’s many components are interdependent—change one, and the effects ripple through the system. Estuaries are subject to tidal influence, mixing salt, brackish, and fresh water at different locations according to seasonal river flows and tides. This estuarine environment once teemed with fish and wildlife and is still essential to hundreds of species from crabs to mammals and fungi to grasses. Some of these are unique to the region, such as the delta smelt and the Antioch dunes evening primrose.
The Delta and Suisun Marsh lie in a central portion of the Pacific Flyway and provide a vital migratory, wintering and breeding habitat for shorebirds and migratory birds. The Delta historically has supported lucrative commercial and sport fisheries of both native and nonnative fish.
In developing policies to revitalize the Delta ecosystem, many ecological roles must be kept in mind. The Delta, the flyway, and the fisheries all provide great value to the State of California, both as tangible economic assets and as a trust that we must steward for future generations.
Delta lands are also important elements of the Delta ecosystem and provide large value to the State of California. Delta levees are vital to protecting water as much as islands and infrastructure and make critical contributions to the successful functioning of the Delta.
The Delta’s ecosystem must be regenerated so that it functions more effectively as an integral part of the San Francisco Bay estuary, combining tidal and river flow patterns within appropriate physical habitat types characteristic of the historical Delta. The Delta must also contain thriving terrestrial habitats and sport and commercial fisheries that have been important to northern California’s culture and economy for decades.
To meet these objectives, the different areas of the Delta will be managed differently.
The Delta ecosystem cannot be returned to its pre-European contact condition, when it was a vast sea-level tidal marsh. It is also facing powerful sources of change including rising sea levels and water temperatures and the prospect of sudden changes in habitat structure caused by levee failures. Given these facts, a desired Delta ecosystem should not be defined in terms of a static “end state,” but rather in terms of the beneficial functions and uses that it provides and the resilience of those functions and uses to external disturbances.