Wetlands and Wildlife
The wetlands and riparian zones along the Estuary’s shores are some of the most ecologically and economically important components of the Bay-Delta system. They provide many benefits, including food-web support, habitat for fish and wildlife, flood protection, water-quality improvement and erosion control. They also provide waterfront open space and recreational opportunities.
Over 300 fish and wildlife species breed, raise young, feed and rest in Estuary wetlands. Over 60 plant and animal species in these wetlands are listed as rare, threatened or endangered, or are candidates for such listing. Hundreds of other species — particularly birds, amphibians, insects and freshwater fish — make their homes in the Estuary’s riparian zones. Beaches and shoreline also offer important breeding sites for harbor seals and nesting spots for aquatic birds.
Human development of the Estuary basin has resulted in the loss or conversion of more than 500,000 acres of tidal wetlands and thousands of acres of shoreline and stream habitat. In the Delta, 97% of the 345,000 acres of historic freshwater wetlands have been converted to other uses, mostly farms. In the Bay Area, 82% of the approximately 200,000 acres of historic tidal and brackish wetlands have been converted to other wetland types and to non-wetland uses. Development has also adversely affected non-tidal wetlands, particularly riparian forest and seasonal wetlands. Wetland loss has slowed substantially since the early 1970s, but continues.
The major human-induced threats to the Bay’s remaining wetlands include highway and bridge construction, airport expansion and other shoreline development. Away from the immediate Bay margin, residential, commercial and industrial development (including associated flood control and transportation projects) threatens seasonal wetlands and riparian corridors. On rural lands, particularly in the counties experiencing high growth rates, wetlands face urban expansion pressure.
Although many of the Estuary’s wetlands have been adversely affected by development, a sizable acreage is now protected in parks, refuges and preserves. In the Bay and Delta, more than 140,000 acres of wetlands are currently safeguarded by public and private entities. This represents about 22% of the Estuary’s remaining wetlands.
Source: State of the Estuary , 1992—1997 (San Francisco Estuary Project: 1997), p. 26