Development of a Multimetric Index for Integrated Assessment of Salt Marsh Condition in the Northeast Coastal and Barrier Network

Science Center Objects

Salt marsh ecosystems along all US coastlines have been altered, degraded, and destroyed by human activities, including ditching and drainage of the marsh platform, tidal restrictions, discharge of pollutants, and introduction of invasive species. The National Park Service conducts long-term monitoring of salt marsh vegetation and nekton (fish and free-swimming crustaceans) to provide information to park managers on how salt marsh ecosystems are changing over time. Multimetric indices allow various indicators of salt marsh condition to be integrated into a composite score for reporting condition. 

The Challenge: The integrity and sustainability of salt marshes in National Park units of the Northeast Coastal and Barrier Network (NCBN) are severely threatened by human activities. These marshes provide critical fish and wildlife habitat and essential ecosystem services in the northeastern coastal zone and are a high priority for NCBN Vital Signs monitoring. Biennial monitoring of nekton (i.e., fish and free-swimming crustaceans) and vegetation has been conducted in NCBN parks since 2008. There is now a critical need for tools to integrate Vital Signs measures in a way that allows assessment of the overall condition of park salt marshes

The Science: We integrated NCBN nekton and vegetation monitoring data into a multimetric index (MMI) for evaluating, predicting, and comparing salt marsh condition at local and regional scales. We applied a theory-based algorithm to NCBN data to guide selection of the optimal set of metrics to include in the MMI. The final product is be a model-driven assessment tool that is maximally sensitive to disturbance, objective, and interpretable. 

The Future: The MMI is being used by NCBN to report trends in the overall condition of park salt marshes over time. This information can be used to guide management decisions aimed at maintaining, enhancing, or restoring the integrity of park ecosystems.