Elkhorn Slough is a coastal wetland and ecological reserve containing one of the largest tracks of salt marsh habitat on the central California coast. The wetland and surrounding watershed provide critical habitats to many diverse species, and the area is home to a growing nature-based tourism industry, year-round agriculture, and several marine science research institutions.
There is a history of environmental initiatives in the area, including strategic land acquisitions for conservation purposes and development of a one-stop permitting package to facilitate voluntary implementation of conservation measures on farmland surrounding the slough. In the past 150 years, nearly 50 percent of the slough’s salt marsh habitats have converted to mudflats due to human alterations of hydrological dynamics in the estuary and nearby upland areas.
In 2004, the Elkhorn Slough National Estuarine Research Reserve (NERR), owned and managed by the California Department of Fish and Game (DFG) in partnership with the National Oceanic and Atmospheric Administration (NOAA), and a local non-profit organization, the Elkhorn Slough Foundation (ESF), initiated a strategic planning process to complement existing environmental efforts and develop restoration strategies with the potential to reduce tidal scour and restore the slough’s important marsh habitats.
The planning process led to the Elkhorn Slough Tidal Wetland Project. With participation of more than a hundred stakeholders representing state, federal, non-governmental, scientific and economic interests, the Tidal Wetland Project team has been investigating the hydrology, nutrient and sediment dynamics, biological communities and socio-economic values of the slough, as well as the political and financial feasibility of four restoration options.
They have chosen to move forward with a low sill (i.e., water control structure) at the mouth of the Parsons Slough complex, which will reduce the tidal prism in this area and allow the project team to evaluate the efficacy of this approach while additional restoration options are still under consideration. The sill will be adaptively managed as water quality, habitats, erosion rates, and wildlife populations are monitored over time.
Mission
The overarching goal of the Elkhorn Slough Tidal Wetland Project (TWP) on the central California coast is “to conserve and restore sustainable estuarine habitats in the Elkhorn Slough watershed through the application of an ecosystem-based management approach."
Specifically, the TWP seeks to enhance understanding of different conservation strategies and select preferred actions to achieve its vision for “a mosaic of estuarine communities of historic precedence that are sustained by natural tidal, fluvial, sedimentary and biological processes in the Elkhorn Slough watershed as a legacy for future generations.”
Objectives
Within the scope of the overarching goal, the TWP has three more-focused objectives:
Seventeen planning principles were articulated by the Strategic Planning Team during the Tidal Wetland Project planning process to guide the effort’s decision-making, including:
Lead Organizations
The Elkhorn Slough Tidal Wetland Project (TWP) on the central coast of California has enlisted over one hundred individuals from different interests and areas of expertise to facilitate its science-based multi-stakeholder effort to restore important salt marsh habitats in Elkhorn Slough.
In addition to the Elkhorn Slough National Estuarine Research Reserve (NERR), which is owned and managed by the California Department of Fish and Game (DFG) in partnership with the National Ocean and Atmospheric Administration (NOAA), and the Elkhorn Slough Foundation, representatives from the following agencies and organizations participate in the TWP:
Key Parties
The Elkhorn Slough Tidal Wetland Project (TWP) on the central coast of California has enlisted over one hundred individuals from different interests and areas of expertise to facilitate its science-based multi-stakeholder effort to restore important salt marsh habitats in Elkhorn Slough.
In addition to the Elkhorn Slough National Estuarine Research Reserve (NERR), which is owned and managed by the California Department of Fish and Game (DFG) in partnership with the National Ocean and Atmospheric Administration (NOAA), and the Elkhorn Slough Foundation, representatives from the following agencies and organizations participate in the TWP:
The Elkhorn Slough Tidal Wetland Project on the central California coast was initiated to reduce tidal scour and restore critical eroding salt marsh habitats in a manner that minimizes impacts on diverse ecosystem components, is based on the best available science and supported by a wide range of community interests.
The effort is managed by staff at the Elkhorn Slough National Estuarine Research Reserve (NERR) - jointly operated by the National Oceanic and Atmospheric Administration (NOAA) and the California Department of Fish and Game (DFG) - in partnership with a Strategic Planning Team and Science Panel.
Other important players in the EBM effort include the Elkhorn Slough Foundation (ESF) and various contracted institutions and consultants. In addition, NERR docents, local community members and peer reviewers participate. Authority to make management decisions and implement project plans varies among TWP participants. The SPT is the decision-making body for the TWP, but it serves more of an advisory role to the TWP participants with actual jurisdiction or land ownership in the area (i.e., DFG and ESF).
The Elkhorn Slough watershed in central California has a history of environmental initiatives. Beginning in the 1980s, the slough was designated as an ecological asset by federal and state agencies. At this time, strategic land acquisitions were made for conservation purposes by the Elkhorn Slough Foundation, The Nature Conservancy, and others. In the 1990s, erosion and nutrient runoff from steep hillside farms adjacent to the slough became a top environmental priority.
The US Department of Agriculture and the Elkhorn Slough Foundation conducted community outreach and education to increase environmental awareness of better land use practices amongst farmers and the visiting public, and together with Sustainable Conservation they developed a one-stop regulatory program for permitting that facilitated farmers’ voluntary implementation of conservation measures on their land.
In 1999, The David and Lucile Packard Foundation awarded funding to The Nature Conservancy to develop a conservation plan for Elkhorn Slough. Through a process that involved more than two dozen stakeholders, a plan was drafted that identified coastal marsh habitat as a critical resource within the watershed, and it identified loss and conversion of marsh habitat, and contamination and sedimentation of remaining marshes, as major threats to the ecosystem.
In 2002, staff at the Elkhorn Slough National Estuarine Research Reserve (NERR), which is jointly operated by the California Department of Fish and Game (DFG) in partnership with the National Oceanic and Atmospheric Administration (NOAA), acknowledged the scale and complexity of the slough’s environmental issues and the need for coordinated input and action from scientific experts, resource managers and community members. Building on past efforts to preserve and restore the ecosystem, the NERR and partners wrote a proposal to the NOAA Coastal Impact Assistance Program for resources needed to initiate a stakeholder-driven science-based process that would develop a coherent and comprehensive vision for the slough and address the spectrum of threats impacting the wetland.
The proposal was approved; however, its budget was significantly scaled back from several million dollars to approximately $2-300,000. As a result, NERR staff scaled the project down and chose to prioritize the threats they perceived to be the most urgent and unaddressed, and that were within their capacity to mitigate given existing resources. They chose to focus, for the time being, on restoration options that will address tidal scour and loss of salt marsh habitat.
The Ecosystem
Elkhorn Slough is the largest tract of tidal salt marsh outside of the San Francisco Bay remaining in California today.The slough itself is a 2,690 acre (10.9 km2) wetland that extends 7 miles (11.3 km) inland from Monterey Bay in central California, which provides important resources to more than 780 species of resident and transient wildlife species, including a disproportionate number of rare, threatened, or endangered species.
In 1979, the National Oceanic and Atmospheric Administration designated 1,439 acres (5.8 km2) of the slough as a member of its National Estuarine Research Reserve program, and since that time large investments have been made in the area for conservation purposes.
The watershed encompassing Elkhorn Slough and nearby Moro Cojo Slough covers approximately 30,292 (122.6 km2) acres and is largely undeveloped with a quarter of the land adjacent to the slough in cultivated agriculture.
The Moss Landing Harbor, located at the entrance of the slough, is one of the most active fishing ports in the state and the area has become an increasingly popular destination for outdoor and nature-based recreational activities.
Several marine research institutions are located in and around the slough, and three highways and a main north-south coastal railroad intersect the waterway. In addition, the largest electricity-generating power plant in California is located at the slough’s mouth.
Threats
In the past, Elkhorn Slough was heavily impacted by erosion and nutrient run-off from steep hillside farms. Through outreach efforts to local farmers, conservation easements and the development of a one-stop regulatory permitting package that enabled farmers to implement voluntary conservation measures on their land, these issues have largely been mitigated.
Today, the slough is considered one of the most threatened ecosystems in California because of the magnitude of its tidal scour and rate of salt marsh habitat loss. Ninety percent of the historic salt marsh area is predicted to disappear by 2050 if no action is taken.
The tidal erosion and marsh loss threats have been attributed to alterations of tidal flow and sediment supply, traced back to 1947 when the mouth of the slough was relocated for the construction of the Moss Landing Harbor. In addition, historical diversion of upland riversforagricultural purposes has reduced downstream flow of fine sediment that traditionally replenished the estuarine plain.
The Tidal Wetland Project is focused primarily on this issue of salt marsh habitat loss; in the next decade it will deal with additional ecosystem threats, including water quality issues resulting from nutrient runoff from nearby agriculture, invasive species and climate change.
Complementing past efforts to preserve and restore land in and around Elkhorn Slough on the central California coast, the Elkhorn Slough Tidal Wetland Project (TWP) was initiated in 2004 to re-establish important salt marsh habitats in a manner that minimizes impacts on the ecosystem as a whole, is based on the best available science and supported by a variety of community interests.
Strategies employed in the process include:
The Elkhorn Slough Tidal Wetland Project (TWP) on the central California coast was initiated to restore critical eroding salt marsh habitats in a manner that minimizes impacts on a variety of ecosystem components, is based on the best available science and supported by a wide range of community interests.
As of June 2009, a restoration project was chosen that will both slow the rate of marsh loss and serve as a learning opportunity for future restoration projects. A low sill – water control structure – will be constructed at the entrance of the Parsons Slough complex, a component of Elkhorn Slough.
Before, during and after the sill’s construction, water quality, biological community composition, marsh habitats and erosion rates will be monitored and subsequent data will be combined with input from scientific advisors and the community. This information will then be reviewed by project team members and relevant resource managers.
The design of the sill will serve as a baseline structure that will be compatible with future additions in height and the degree of tidal restriction, which will enable the project team to carefully evaluate the trade-offs of further tidal restriction over the course of several years and, specifically, assess the sill’s impacts on sediment loss, water quality and wildlife in Parsons Slough.
This incremental approach will provide an opportunity to gradually restore a portion of Elkhorn Slough while updating expectations of outcomes for potential larger restoration options based on measured changes.
The Elkhorn Slough Tidal Wetland Project (TWP) on the central California coast was initiated to restore important subsiding salt marsh habitats in a manner that minimizes impacts to the ecosystem as a whole, is based on the best available science and supported by a range of community interests.
This effort is building on three decades of past environmental initiatives in the area. Past efforts mitigated the impacts of erosion and nutrient runoff from steep hillside farms adjacent to the slough and strategically acquired land for conservation purposes. Since initiation of the TWP in 2004, project team members and the community have come together to discuss their visions for the system and explore strategies for restoring important salt marsh habitats.
Much progress has been made towards attaining a better understanding of the Elkhorn Slough ecosystem as a variety of studies have been conducted on the area’s hydrology, nutrient and sediment dynamics, wildlife populations and socio-economic values, which helped parameterize models being used to make predictions of future conditions in the slough under different restoration scenarios.
In 2009, a decision was made to proceed with the construction of a water control structure at the entrance to the Parsons Slough complex, a component of Elkhorn Slough. The structure will allow adaptive management and will inform future considerations of larger restoration options. Construction will soon be underway.
In addition, the TWP has joined other EBM initiatives in creating an EBM network on the US west coast of the United States, and knowledge gained regarding EBM implementation is being shared with interested parties through a variety of venues.
The Tidal Wetland Project in Elkhorn Slough on the central California coast was initiated to restore critical eroding salt marsh habitats in a manner that minimizes impacts on a range of ecosystem components, is based on the best available science and supported by a wide range of community interests
It has been facilitated by five key factors:
The Elkhorn Slough Tidal Wetland Project (TWP) on the central California coast was initiated to restore important subsiding salt marsh habitats in a manner that minimizes impacts on a range of ecosystem components, is based on the best available science and supported by a range of community interests.
The TWP’s efforts have been challenged by a number of issues:
The Elkhorn Slough Tidal Wetland Project (TWP) on the central California coast was initiated to restore important salt marsh habitats in a manner that minimizes impacts on diverse ecosystem components, is based on the best available science and supported by a wide range of community interests.
Through the TWP process, project team members have learned:
Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve Website: http://www.elkhornslough.org
Elkhorn Slough Ecosystem-Based Management Webpage: http://www.elkhornslough.org/tidalwetland/ebm.htm
Elkhorn Slough Tidal Wetland Project Webpage: http://www.elkhornslough.org/tidalwetlandproject/index.html
“About the TWP” Webpage: http://www.elkhornslough.org/tidalwetland/description.htm
“Links to Partners and Friends of Elkhorn Slough”: http://www.elkhornslough.org/links.htm
ESNERR Research Program Webpage: http://www.elkhornslough.org/research.htm
Monitoring Program Webpage: http://www.elkhornslough.org/research/monitor_main.htm