The effect of long-term marsh management on land-loss rates in coastal Louisiana

Louisiana's coastal wetlands have been actively and passively managed since the 1950s to reduce land loss, change plant composition, control water levels, and determine properly boundaries, among other reasons. Marsh management is the primary technique that has been used in Louisiana to try to stow or halt dramatic wetland losses (0.8%/yr from 1955 to 1978, or 288,000 ha). Because of the large amount of Louisiana's coastal wetlands under management and the high cost associated with marsh management, it is important to determine if those efforts have been successful. The purpose of this study was to determine ii land-loss rates were changed as a result of marsh management. This study used data from a previous study and additional new data. Data for 13 paired managed and unmanaged sites (total area = 22 x 10(3) ha) studied previously were obtained, expanded, and tested statistically to provide empirically Valid conclusions over a longer management period than previously available (1-32 years compared to 6-37 years). There was no statistically significant difference between managed and nearby reference sites. The effects of changes in the regional environment appear to have had much greater influence on the land-loss rates than did management at individual sites.