Wetlands in Southern California include freshwater, saltwater and brackish-water marshes, swamps and mud flats. Marine wetlands develop where streams enter the ocean across a low, flat coast, and are modified by differences in salinity and by the tidal cycle. Wetlands help mitigate flooding, filter and recharge groundwater, and provide feeding and breeding habitat for fish and waterfowl.
There are ten brackish wetlands along the edge of Santa Monica Bay, the largest of which are the Ballona Wetlands Complex (Ballona Wetlands, Ballona Lagoon, Del Rey Lagoon) and Malibu Lagoon.
At one time, the Ballona Complex was 2,100 acres of coastal estuary and wetlands. Many factors contributed to its decrease in size; today it covers approximately 430 acres. These factors include: the development of Marina del Rey, the Venice canals, and other residential and commercial properties; the draining of wetlands for agricultural use and to control insects; and the creation of a concrete channel to replace Ballona Creek. The 260-acre Ballona Wetland is the largest remaining wetland within this complex. The site is a mixture of habitats dominated by coastal salt marsh. The 16-acre Ballona Lagoon is an artificially confined tidal channel that connects the Venice canals to the Pacific Ocean.
The 40-acre Malibu Lagoon, at the mouth of Malibu Creek, is also a remnant of a larger system.
Most local wetlands support less biological diversity and are less productive because of their degraded condition. Restricted water flow, which results in poor water quality (high levels of nutrients and/or contaminants), is the main concern at most sites. Additional adverse impacts include the lack of shallow water habitat, disruption of upstream flow, introduction of non-native plants and animals, debris and bacteria from urban runoff, and recreational over-use.
The wetlands of Santa Monica Bay support a variety of marine and terrestrial life, however, many of the species characteristic of pristine salt marshes of Southern California are lacking. Vegetation is often sparse and includes or is dominated by introduced species which often compete with native species. The salt-marsh bird's beak (a federally- and state-listed endangered plant) is no longer found in the area. Belding's savannah sparrow (a state-listed endangered species) is a year-round resident of salt marshes, foraging and nesting in pickleweed, a dominant plant of the upper marsh. The population of this sparrow was low but stable until 1990, when it began to decline, in part because of predation by introduced red foxes. Attempts to remove the foxes have met with limited success.
Other "listed" birds which have not been seen for some time (due to the absence of cordgrass) are the light-footed clapper rail and the black rail. The black-necked stilt, another species of concern, has not nested recently in local wetlands.
Animal communities in the sediments, lagoons and channels of local wetlands are also less diverse than in the past; in fact, some of the most abundant invertebrates found now are indicators of stressed conditions. Populations of some fish species, such as steelhead trout, have decreased to precariously low numbers. The tidewater goby was recently reintroduced to its original habitat at Malibu Lagoon, although its survival is far from guaranteed.
Although several plans have been developed to preserve and restore Santa Monica Bay wetlands, attempts have often been hampered by the complex issues associated with wetlands restoration. The SMBRP has mapped and inventoried the Bay's remaining wetlands and has targeted key areas for restoration, enhancement, and protection. Habitat restoration plans are an important feature of the Bay Restoration Plan.