Louisiana coastal wetland loss

A series of diversion projects have been implemented to reintroduce freshwater and sediment from the Mississippi River into Louisiana coastal wetlands (Figure 18.9). A recent study examined the impact of Mississippi River freshwater diversion on enhancing vertical marsh accretion (mineral and organic matter accumulation) in Breton Sound estuary, a coastal wetland experiencing marsh deterioration as a result of subsidence and saltwater intrusion (DeLaune et al., 2003). The Caernarvon diversion has positively impacted marsh accretion in Brenton Sound estuary helping to slow or reverse wetland loss. Several hundred hectares of new marsh have been created by the introduction of Mississippi River water into the system (Villarrubia, 1998). 

Leibowitz, S. G. and J. M. Hill. 1987. Spatial analysis of Louisiana coastal land loss. In R. E. Turner and D. R. Gaboon (eds.) Causes of Wetland Loss in the Coastal Central Gulf of Mexico. Volume II Technical Narrative. Final report submitted to minerals Management Srvice, New Orleans, LA. Contract No. 14-12-001-30252. OCS Study/MMS 87-0120. 400 pp. 

Much of the wetland loss occurring in coastal Louisiana is due to the deterioration of highly organic marsh soil. As discussed earlier, conversion of coastal marshes to inland open water is associated with plant stresses such as saltwater intrusion into nonsaline marshes and increased soil waterlogging as a result of subsidence. Marsh elevation decreases rapidly following plant mortality because of the structural collapse of the living root networks (DeLaune et al., 1994). The peat collapse and the associated erosion result in the conversion of marsh into open water. Conversions to open water system releases a considerable amount of carbon into the estuary where it is either decomposed or... 

Barras j. a., Bourgeois P. E. and Handley L. R. (1994) Land loss in coastal Louisiana 1956-1990. National Biological Service, National Wetlands Research Center, Open File Report 94-01, 4 p, 10 color plates. 

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