THE EFFECT OF COASTAL ALTERATION ON MARSH PLANTS 



Robert H. Chabreck 



School of Forestry and Wildlife Management 



Louisiana State University 



Baton Rouge, LA 70803 



ABSTRACT 



The Louisiana coastal marsh is subdivided into four vegetative types: saline, 

 brackish, intermediate, and fresh. The types occur in bands generally paralleling the 

 coastline and contain characteristic water salinity levels and plant communities. 

 Activities of man coupled with natural processes, such as subsidence and erosion, have 

 removed many natural tidewater barriers and reduced freshwater flow through the 

 marshes. As a result, saltwater intrusion from the Gulf of Mexico has increased and the 

 boundaries of vegetative types hove been altered. The saline vegetative type has greatly 

 increased in size and the brackish and intermediate types have shifted inland. This has 

 caused a drastic reduction in the size of the fresh vegetative type. 



INTRODUCTION 



The coastal marshes of Louisiana are one of the most productive habitats for fish 

 and wildlife in North America. The high production of fish and wildlife is directly 

 related to the abundance and diversity of photosynthetic plants produced within the 

 area. These plants are the basic source of energy for dependent animal populations, and 

 conditions enhancing plant growth serve to benefit fish and wildlife. On the other hand, 

 activities which alter environmental conditions can be detrimental to plants and 

 drastically affect fish and wildlife populations. 



Activities which have had the most damaging impact on marsh vegetation are canal 

 construction associated with oil and gas exploration, pipelines, navigation, and flood 

 control; permanent drainage for agriculture, industry, and urbanization; modified 

 drainage patterns associated with levee and highway construction and spoil deposits; and 

 dredge and fill operations. The activities of man coupled with natural processes such as 

 subsidence and erosion have greatly altered environmental conditions and thereby 

 changed the distributional patterns of plants. Only with a complete understanding of the 

 distributional patterns and the environmental conditions necessary for optimum plant 

 growth can the magnitude of coastal alteration be assessed. 



THE COASTAL REGION OF LOUISIANA 



Marshes of the Louisiana coastal region encompass an area of approximately 1.7 

 million ho and span the full coastline of the State. The marshes extend inland for 

 distances ranging from 24 to 80 km and reach their greatest width in southeastern 

 Louisiana. 



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