It is estimated that in the last 150 years, approximately 90% of San Francisco Bay’s tidal wetlands have been lost or seriously degraded. This occurred mainly through diking of wetlands previously considered useless in order to develop arable land and salt production ponds and through the progressive filling of wetlands and the Bay itself for military, industrial and residential uses. During the early to mid-20th century many cities viewed the Bay and its adjacent wetlands as a void to be filled in order to meet the demands of an expanding population and to increase their tax base. Shoreline development occurred so rapidly that by 1950, only about 50,000 acres of tidal marshes remained, a quarter of the historic amount.
Had it not been for visionary conservationists such as Catherine Kerr, Sylvia McLaughlin and Ester Gulick, who founded Save the Bay in 1961, it is possible that developers and cities would have continued filling the Bay and its tidelands. Their efforts protected key areas from development and led to the passage of the McAteer Petris Act in 1965, which created the Bay Conservation and Development Commission with a mandate to prevent unregulated filling of the Bay. Soon thereafter, due to the tireless efforts of the founders of Citizens Committee to Complete the Refuge, a bill passed into law in 1972 establishing the Don Edwards San Francisco Bay National Wildlife Refuge, the first and largest urban wildlife refuge in the United States.
Since the 1970s, more than 50 tidal restoration projects have been implemented around the Bay. Most significantly, the South Bay Salt Pond Restoration Project intends to restore 15,100 acres of industrial salt ponds to tidal wetlands and other habitats.
Despite the on-going efforts of several local conservation groups, portions of historic baylands and tidal marsh are still under threat from development. This includes historic tidal marshes in Newark and salt pond areas currently under water in Redwood City. With the added threat of sea level rise, development in such areas is entirely inappropriate from not only a wetland protection and ecological point of view but also in terms of flood risk and human safety.
Uncertain Future of Wetland Protection
Wetland restoration projects attempt to restore a portion of historic wetlands already lost to development, yet several factors may impede the long-term success of this approach.
Large portions of land adjacent to San Francisco Bay have gradually subsided as a result of drainage, agriculture and urban development. As a result, restoration efforts must account for this loss in elevation with fill of soil and sediment. Historically, the Sacramento-San Joaquin Delta naturally provided ample sediment to the Bay to make up for a certain degree of subsidence. Yet in the last decade, U.S. Geological Survey researchers have observed significant reductions in suspended sediment loads to the Bay, which limits the rate of natural sediment build-up, or accretion. As sea levels rise, existing wetlands and tidal flats may not be able to attract enough sediment at rates approaching those of sea level rise. As a result, large expanses of restored and intact wetlands may become submerged by the end of the 21st century.
Research is ongoing to determine which wetlands are at risk from sea level rise and whether additional management strategies can preserve our existing wetlands. In 2011, BCDC revised its Bay Plan to include policies which would require cities and developers to sensibly consider the likely effects of sea level rise for the purposes of public safety and conservation of wetlands and transitional upland habitats. These policies would place limits on the types of development considered appropriate in areas under BCDC’s jurisdiction which are at threat of sea level rise, while requiring developers to conduct assessments to determine flood risk. Baykeeper actively supported the Bay Plan amendment and helped secure its passage in October 2011.
While the days of large-scale filling of the Bay are largely over, the Bay is still at threat from developers that stand to profit from filling of the Bay or developing its shorelines. Such immediate threats are magnified by factors largely outside our control, such as decreased sediment loads and potentially rapid sea level rise. Baykeeper will continue to advocate for plans and policies favoring wetland protection and to support local organizations working to protect open spaces around the Bay.