THE USE OF BASIC RESEARCH IN WETLAND 

 MANAGEMENT DECISIONS 



Irving A Mendelssohn 



and 



Karen L. McKee 



Laboratory for Wetland Soils and Sediments 



Center for Wetland Resources 



Louisiana State University 



Baton Rouge, LA 70803 



ABSTRACT 



Nature and humans are rapidly deteriorating wetlands in coastal Louisiana. The rate of wetland 

 loss is expected to increase as increased atmospheric warming accelerates the rise in eustatic sea 

 level. The first step in the rehabilitation of specific degraded wetlands is to determine why 

 vegetation no longer establishes itself within these marshes. We have conducted a series of field 

 experiments based on classical bioassay techniques that provide insight into the proximal causes for 

 wetland deterioration as well as potential mechanisms for restoring brackish marshes. Field 

 transplant experiments demonstrated that brackish marshes can be negatively affected by both 

 saltwater intrusion and subsidence. However, the ability to restore a deteriorated brackish marsh 

 in Louisiana was not controlled by salinity, but rather by the degree of plant inundation and soil 

 reduction resulting from hydrology and lowered marsh surface elevation. These data support the 

 hypothesis that marsh restoration can be accomplished by sediment additions and through 

 revegetation with appropriate plant species. 



INTRODUCTION 



Louisiana is experiencing one of the greatest rates of coastal deterioration in the world with land 

 loss equaling 130 km 2 /yr (Gagliano 1981) and increasing exponentially during the past 100 years 

 (Turner et al. 1982). Much of this land loss is expressing itself in the deterioration of Louisiana's 

 coastal wetlands, from saline herbaceous salt marshes on one extreme to freshwater swamps on the 

 other. For example, from 1955 to 1978, 188,000 ha of Louisiana's coastal wetlands within the 

 Mississippi River deltaic plain have deteriorated into open water bodies (Wicker 1980). In the 

 midst of this high rate of coastal land loss, the State of Louisiana is searching for a better 

 understanding of the causes of wetland degradation and management procedures to reduce the rate 

 at which it is occurring. As a result of the worldwide rise in sea level, other coastal States may 

 also experience marsh deterioration resulting from increased water levels. 



Although the ultimate causes of wetland deterioration in Louisiana-land subsidence, sediment 

 deprivation, leveeing of the Mississippi River, artificial canals, and saltwater intrusion-have been 

 identified (Boesch 1982; Mendelssohn et al. 1983; Turner and Cahoon 1987), their mode of action 

 is little understood and often hotly debated by agencies mandated to protect and manage the 

 Louisiana coastal zone. The lack of understanding of the immediate causes of wetland degradation 

 is certainly understandable when one considers the complexity of the problem-the interaction of 

 natural and human-induced stresses whose effects may vary greatly depending on the particular 

 wetland plant community affected. 



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