Recent Changes in the Extent of Estuarine Wetlands in Southern California: Pt. Piedras Blancas to Santa Monica

Abstract

The fragmentation and loss of southern California estuarine wetlands during the last century is a well documented phenomenon. Less clear are the relatively recent changes in estuarine acreage since the 1970s following the passage of several federal and state laws aimed at protecting coastal wetlands (e.g. California's Coastal Act and Coastal Conservancy Acts of 1976 and the Federal Clean Water Act of 1977). We updated 40 National Wetland Inventory (NWI) maps of the California Coast, between Pt. Piedras Blancas and Santa Monica, CA, using 1994 Digital Ortho Quarter Quads. Updated maps were compared with 1976 aerial photographs used to develop the original NWI maps of the area. Our results indicate there has been a net gain of 0.2%, or 6.5 hectares, in estuarine and freshwater tidal wetland acreage between 1976 and 1994. The lack of significant changes in estuarine wetland acreage implies federal laws, such as the Clean Water Act, Coastal Zone Management Act, and California's Coastal Act have been largely successful in stemming the loss of estuarine habitat. However, our data does not provide information on the health of these wetlands which are influenced by the indirect effects of urban development such as non-point source pollution, sedimentation, flood control schemes, and invasive species.