As delineated in the North American Bird Conservation Initiative, the Gulf of Mexico marshes (Region 28*) extend roughly from the Mississippi-Louisiana state boundary west and south to the mouth of the Rio Grande. This region also includes a large area of land that formerly was tall grass prairie interspersed with wetlands that today is largely converted to agricultural production.
The NAWMP GCJV divides the coastal marsh of Louisiana into separate but related initiative areas, the Mississippi River Coastal Marshes (Deltaic Plain) and the Chenier Plain (Gulf Coast Joint Venture 1990). Similarly, in Texas the coast is subdivided into 3 initiative areas, the Upper Texas Coast (Chenier Plain), the Mid-Texas Coast, and the Lower Texas Coast (Laguna Madre). Adjacent to and immediately north of the Chenier Plain and Texas Mid-Coast regions is a band of agricultural land dominated by rice production, sometimes referred to as the wet prairie or rice prairie. This region probably increased in importance to waterfowl when it was converted from wet tall grass prairie to rice agriculture (Hobaugh 1984, Hobaugh et al. 1989, Stuzenbaker 1980, 1984).
The characteristics of the Deltaic Plain historically were driven by the dynamics of the lower Mississippi River. Delta formation processes interacted with the Gulf of Mexico to give rise to a diverse ecosystem ranging from bottomland hardwood swamps and low-energy freshwater marshes to high-energy tidally influenced salt marshes. The Chenier Plain also is tied to Mississippi River Delta activity. When the Mississippi River was active in the western reaches of its delta, sediment was carried westward by near shore Gulf currents and deposited on mudflats that resulted in creation of the Chenier Plain region. Alternatively, when the river shifted east, near shore current carried fewer sediments and eroded shoreline and marsh. The Chenier Plain and wet prairie periodically are interrupted by rivers that drain upland areas to the north. A thorough review of Mississippi River delta formation processes and effects is presented in Louisiana Coastal Wetlands Conservation and Restoration Task Force (LCWCRTF 1998).
*Region 28 - NABCI Bird Conservation Region 37