Sentinel Monitoring of Salt Marshes in the South Slough National Estuarine Research Reserve
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Posted byRachel Gregg
The South Slough National Estuarine Research Reserve (NERR), along with several other NERRs, acts as a sentinel site to monitor climate change impacts. The reserve is engaged in several long-term ecological monitoring programs to determine the effects of sea level rise, warmer temperatures, and coastal storms on species and habitats.
The South Slough NERR is a 4,771-acre reserve comprised of open water channels, freshwater wetlands, tidal and salt marshes, and forests. Key management issues for the reserve include habitat degradation, watershed health, invasive and non-native species introductions, and climate change. One of the overriding goals of the South Slough NERR is to use an adaptive management approach in addressing these concerns.
Salt marshes on the west coast of the United States are fairly sparse and small in acreage; Oregon has approximately 7,000 acres of salt marsh. These marshes provide valuable habitat and refuge for fish, crabs, and other wildlife, and important ecosystem services by filtering water and protecting shorelines from erosion during strong coastal storms. This habitat is threatened by climate change; impacts of concern include sea level rise, warmer temperatures, more intense and frequent coastal storms, salinity intrusion, and erosion.
The South Slough NERR was part of a national effort, created in 2007, to establish salt marshes as long-term reference sites at five reserves (Narragansett; Wells, Maine; Chesapeake Bay, Virginia; North Carolina; South Slough, Oregon) to compare marsh restoration success. Additionally, the reserve, along with other NERRs, participates in the System Wide Monitoring Program (SWMP), tracking changes in water quality, plants, animals, and habitats within the reserve over time. SWMP provides real-time NERR data and allows users to compare variables between reserves over different time periods.
The NERR System and NOAA Restoration Center partnered on a project—created in 2007—to establish salt marshes as long-term reference sites at five reserves (Narragansett; Wells, Maine; Chesapeake Bay, Virginia; North Carolina; South Slough, Oregon). The project was funded through the National Oceanic and Atmospheric Association to 1) use natural marshes as references to understand what is happening at restored marshes, and 2) use these natural reference sites to understand how marshes across the United States are responding to the impacts of climate change. The project required the reserves to conduct effectiveness monitoring of 17 Estuary Restoration Act-funded projects at paired restoration and reference sites. The study used a restoration performance index (RPI) to compare different salt marsh characteristics (e.g., salinity, vegetation cover, flow patterns, peat soils) at natural marsh reference sites and recently restored marsh sites over a two-year period (2008–2010) to track water levels and marsh height in order to determine if and how salt marshes can respond to environmental changes, including sea level rise. The South Slough NERR compared results between two reference sites (Danger Point, Yaquina [“Y28”]) and two restoration sites (Kunz Marsh, Yaquina [“Y27”]). The study determined that the restoration of hydrologic processes across the five NERRs were quite high while biological processes (e.g., species density, vegetation composition) varied as coastal marsh plant community development may lag in recovery (see Evaluating Tidal Wetland Restoration Performance Using National Estuarine Research Reserve System Reference Sites and the Restoration Performance Index).
In 2010, reserve staff helped facilitate the development and implementation of a Partnership for Coastal Watersheds (PCW). The foundation of PCW’s work is based on the “triple bottom line” with their committee striving to thoroughly examine all social, economic, and environmental factors when planning for the future. In 2012, the PCW published an action plan, which specifies 37 priority actions that serve as a roadmap for South Slough projects. A comprehensive coastal infrastructure plan regarding sea level rise and a climate change vulnerability assessment ranked in the top five of PCW’s priorities. Coupled with the action plan, PCW published a State of the South Slough and Coastal Frontal Watersheds report based on reserve research. Key findings from the report include:
- Sea level rise rates on the South Coast of Oregon are higher than the global average;
- The pH in the South Slough has increased since monitoring began in 1995 despite the trend of decreasing pH in the greater Pacific Ocean;
- Between the 1970s and 2005, the average height of the tallest third of waves, or “maximum significant wave height,” increased from 9 to 12 meters; and
- Marsh sediment accretion is currently occurring faster than sea level rise, but sea level rise is expected to accelerate; the acceleration will outpace the accretion rate if sea level rise reaches 6.6mm/year.
The undercutting and collapse of coastal cliffs, damage to port facilities, and storm surge inundation of coastal communities are all likely consequences of expected sea level rise.
More recently, the South Slough NERR published an updated 2017–2022 management plan. Unlike the previous plan, this version is priority-based with climate change listed at the top. The four climate action goals are to further the reserve’s understanding of the effects of sea level rise within the South Slough; assess the estuarine impacts of ocean acidification; increase reserve understanding of the relationship between ecosystem functions and climate change; and improve reserve communications about climate change to diverse audiences.
Outcomes and Conclusions
In general, NERRs can be particularly useful as long-term reference sites in a changing climate as they are protected areas that undergo regular long-term monitoring of environmental changes. The data collected may be used to inform other restoration efforts and coastal management.
South Slough National Estuarine Research Reserve Management Plan (2017-2022)
State of the South Slough and Coastal Frontal Watersheds
Partnership for Coastal Watersheds Action Plan
National Estuarine Research Reserve System-Wide Monitoring Program Data
Evaluating Tidal Wetland Restoration Performance Using National Estuarine Research Reserve System Reference Sites and the Restoration Performance Index (RPI)
Gregg, R. M. and J. Sheldon. (2021). Sentinel Monitoring of Salt Marshes in the South Slough National Estuarine Research Reserve [Case study on a project of the South Slough National Estuarine Research Reserve]. Version 2.0. Product of EcoAdapt’s State of Adaptation Program. (Last updated June 2021)