This spring Gulf of Mexico scientists from state, federal, academic and non-profit organizations led by the Northern Gulf of Mexico Sentinel Site Cooperative and the USGS National Wetlands Research Center were the first to compile and publicly share a comprehensive inventory of Surface Elevation Tables, or SETs, for the entire U.S. portion of the Gulf of Mexico. This was a very large accomplishment for two reasons: 1) there are hundreds of SETs in the northern Gulf of Mexico; 2) SETs are typically managed by individual scientists.
What is a Surface Elevation Table (SET)?
A SET is a way to very precisely measure elevation changes in coastal habitats such as marshes and mangroves. Often researchers couple SETs with marker horizons and process-based measurements to estimate how much surficial processes (e.g. sediment deposition or erosion) are contributing to changes in elevation vs sub-surface processes (e.g. root growth, decomposition, compaction, subsidence) (see figure). For example, if there is 3 mm of deposition indicated by the marker horizon but only 2 mm of elevation increase indicated by the SET, then the researcher would know that subsurface processes had caused a loss of 1 mm of elevation.
Understanding how elevation is changing in coastal ecosystems is critical for predicting the ecological effects of local sea-level change, storm surge and nuisance flooding. Coastal habitats, such as marshes and mangroves ,provide nursery grounds, storm impact mitigation, flooding relief and many other services for coastal communities. Without a solid understanding of how the elevations of these ecosystems are changing, it is difficult to assess the stability of these systems and the resultant change in ecosystem services. In Louisiana for example, subsidence rates are high which means a small increase in global sea-level will be compounded by lowered land elevation and result in a greater local change in sea-level relative to the elevation of coastal ecosystems. Together, these factors can results in conversion to open water (i.e., wetland loss). You can see more examples of this at NOAA’s sea-level trends website here.
Having an inventory of all SETs in the northern Gulf of Mexico will improve resource use and will encourage cross-agency data integration. A visually displayed SET inventory highlights gaps and will help managers utilize resources to install and maintain SETs in areas that have gaps. Additionally, this will improve collaboration and regional data products from across the Gulf Coast.
Finally, and most encouragingly, sharing the locations of these SETs demonstrates that there is a strong, collaborative network among researchers, agencies and organizations across the northern Gulf of Mexico dedicated to addressing sea-level rise and helping coastal communities be as resilient as possible.
The Coastwide Reference Monitoring System (CRMS) in Louisiana has the largest network of SETs in the world and is already displaying their data online. The inventory, developed by the Northern Gulf of Mexico Sentinel Site Cooperative and the USGS National Wetlands Research Center, is published on the Gulf Coastal Plains and Ozarks Landscape Conservation Cooperatives (LCC) Conservation Planning Atlas and can be seen here.