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Assessing the health of coastal wetlands nationwide

Salt Marsh at Chassahowitzka National Wildlife Refuge. Credit: Amber Breland/USFWS.

Satellite data products are helping land managers quickly evaluate the health of vulnerable coastal wetlands.

Salt marshes protect communities and infrastructure from storms, filter pollution, and provide habitat for fish and shellfish. These coastal wetlands and the ecosystem services they provide are increasingly threatened by rising sea levels, erosion, and land use change, and land and resource managers need tools to track changes and trends in their health and extent. Satellite data products provide one method for quickly evaluating marsh vulnerability to environmental change and can help inform efforts to restore and protect coastal wetlands.

Salt marsh resilience can be evaluated through a metric called the UnVegetated-Vegetated marsh Ratio (UVVR), developed by the USGS, which measures how much vegetation a marsh area contains and provides an indicator of its overall health.1 Using Landsat 8 satellite imagery, USGS scientists mapped the UVVR at a 30-meter resolution for the coastal wetlands of the contiguous United States for 2014–2018.2 This product enables DOI, state managers, and other users to get broad assessments of the most vulnerable marshes without requiring site-specific studies.

Regular delivery of updated UVVR assessments supports marsh restoration efforts by the National Park Service, the U.S. Fish and Wildlife Service (USFWS), and state agencies. The new data products and national map of UVVR complement detailed mapping by the USFWS’ National Wetland Inventory program and can also be combined with the Coastal National Elevation Database to generate national estimates of marsh lifespan under varying sea level rise scenarios. UVVR data is available in the USGS Coastal Change Hazards Portal.

1 Ganju, N., Defne, Z., Kirwan, M. et al. Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes. Nat Commun 8, 14156 (2017).

2 Couvillion, B.R., Ganju, N.K., and Defne, Z., 2021, An Unvegetated to Vegetated Ratio (UVVR) for coastal wetlands of the Conterminous United States (2014-2018): U.S. Geological Survey data release,