Elkhorn Slough is an exceptional ecosystem on the central California coast providing a key linkage between land and sea. The slough harbors California’s largest tract of tidal salt marsh outside San Francisco Bay. Elkhorn Slough tidal habitats encompass extraordinary biological diversity, providing critical habitat for more than 135 aquatic bird, 550 marine invertebrate, and 102 fish species. The Elkhorn Slough is also home for sea lions, harbor seals, and California sea otters. More than 200 different bird species use the slough as a resting spot during their annual migration.
The upland habitats within the watershed include three of the top ten most imperiled U.S. habitats: freshwater wetlands, coastal prairie, and maritime chaparral. These systems are amazingly diverse, coastal prairie being the most species rich grasslands in north America.
Along with providing habitat for a diverse range of life, wetlands provide a critical service to the environment. Wetlands provide a buffer from land to sea – protecting the water from soil erosion and the land by reducing the impact of flooding. As natural filters, wetlands can remove impurities from the water before it enters our streams and oceans. Wetlands also have been proven to be carbon sequesters -- removing and storing greenhouse gases from the earth’s atmosphere, slowing the onset of global warming.
Estuaries like Elkhorn Slough are among the most threatened ecosystems in California, facing rates of habitat loss between 75 and 90 percent. As a result, a disproportionate number of rare, threatened, and endangered species reside in these areas. In the Elkhorn Slough watershed, two dozen species are included in these categories. Recognizing the value of these resources to the country, the National Oceanic and Atmospheric Administration designated areas of Elkhorn Slough as part of the Monterey Bay National Marine Sanctuary and as a National Estuarine Research Reserve.
The California Department of Fish and Wildlife has also designated parts of Elkhorn Slough as a State Ecological Reserve and as a Wildlife Management Area, as well as designating three marine protected areas: the Elkhorn Slough State Marine Reserve and Conservation Area and the Moro Cojo State Marine Reserve. The National Audubon Society includes the slough in its Globally Important Bird Areas and the Western Hemisphere Shorebird Reserve Network designated it a Site of Regional Importance. The Nature Conservancy and Elkhorn Slough Foundation have invested in protecting over 3,500 acres of this watershed. These multiple designations and strategic land acquisitions reinforce the importance of this place as a key conservation asset.One of the remarkable features of Elkhorn Slough is the diversity of human uses represented in a small watershed. The slough hosts the largest electric power generating plant in California. Additionally, the Moss Landing Harbor, at the entrance to the slough, is one of the most active fishing ports in the State. Elkhorn Slough is flanked by major transportation corridors including three state highways and the main north-south coastal rail line for the Union Pacific Railroad. One quarter of the land in the Elkhorn watershed is in agriculture, with farms in this area producing a significant proportion of the State’s strawberry crop. Residential housing is an increasing factor while recreational activities, including boating, kayaking, and birding, have increased dramatically over the past decade.