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Has marsh dieback been observed before in Louisiana or elsewhere?

Yes, it is not unusual for salt marshes to experience dieback in small patches in some years. However, these areas are usually less than an acre or so in size and generally regenerate the next year or over the next several years. Smooth cordgrass marshes on the coast of Texas have died in small patches ranging from 2-5 acres. But no dieback as extensive as the current Louisiana condition has been observed in recent history.

The phenomenon of marsh dieback (or brown marsh) has been observed along Louisiana's coastline. Hardest hit is the Barataria-Terrebonne estuary extending from the west side of the Mississippi River to the Atchafalaya River. Least affected marshes appear to be those lying east of the Mississippi River.

The Barataria-Terrebonne intertidal salt marshes, which are mostly composed of smooth cordgrass (Spartina alterniflora), cover approximately 390,000 acres. About 110,000 acres have been "severely impacted"; of those acres, at least 17,000, or about 4%, have converted from dense vegetation to open mud flats with little or no vegetation.

About 150,000 acres are considered "moderately impacted". In the moderately impacted areas, green marsh can still be seen, but the marsh has a significant degree of browning. About 137,000 acres of the entire 390,000 acres of intertidal Spartina alterniflora in the Barataria-Terrebonne estuary are considered "normal".

Learn more:

Salt Marsh Dieback in Coastal Louisiana: Survey of Plant and Soil Conditions in Barataria and Terrebonne Basins, June 2000-September 2001

Global Change Impacts on Mangrove Ecosystems (USGS Fact Sheet 2004-3125)

Tags: Ecosystems, Biodiversity, Ecology, Marsh, Wetlands, Water, Vegetation, Coasts, Rivers, Streams, Measurement, Analysis