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 over 135 aquatic bird, 550 marine invertebrate, and 102 fish species.
Estuaries like Elkhorn Slough are, however, 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 Game 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. 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.
Shorebird species at Elkhorn Slough include:
Ecology & Conservation
1) Loss of salt marsh vegetation due to ongoing erosion along the main channel of Elkhorn Slough. Since the construction of the Moss Landing Harbor in 1947, the resulting increase in tidal volume entering the slough has transformed what was formerly a depositional environment into a system exposed to persistent erosion and tidal scour.
2) Introduced invertebrate species. Invasion by non-native invertebrate species, such as Batillaria attramentaria, pose ecological changes of unknown consequence to the natural system. Effects on shorebirds are yet unknown.
3) Agricultural runoff and chemical contamination of water and sentiment. High levels of pesticides have been recorded in the slough.
4) Introduced mammalian predators. Feral red fox and cats threaten nesting shorebirds in the region. Mammalian predators are actively controlled on the salt ponds during the Snowy Plover breeding season.
5) Increasing human impact (e.g., disturbance, garbage.)
6) Train derailing or oil spill. Railroad tracks are located along the main axis of the slough and are traveled daily by trains, often carrying hazardous materials.
Research and Management Activities:
The Elkhorn Slough National Estuarine Research Reserve and Elkhorn Slough Foundation, together with numerous partners, are working to conserve and restore the slough and its watershed. Conservation activities include land acquisition and management, weed abatement, and wetland restoration. The research reserve also coordinates an extensive monitoring and research program. For more information see www.elkhornslough.org
Docent Training Program at the Elkhorn Slough Reserve
Elkhorn Slough National Estuarine Research Reserve
1700 Elkhorn Road
Watsonville, California 95076