The wetlands of Louisiana are water-saturated coastal and swamp regions of southern Louisiana, often called 'Bayou'. The Louisiana coastal zone stretches from the border of Texas to the Mississippi line and comprises two wetland-dominated ecosystems, the Deltaic Plain of the Mississippi River (unit 1, 2, and 3) and the closely linked Chenier Plain (unit 4). The Deltaic Plain contains numerous barrier islands and headlands, such as the Chandeleur Islands, Barataria Basin Barrier Islands, and Terrebonne Basin Barrier Islands. The Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) program, through the NOAA Habitat Conservation National Marine Fisheries Service funded $102 million in construction for deteriorated wetlands and barrier island habitats. Geography The Environmental Protection Agency defines wetlands as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration water to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions (e.g. swamps, bogs, fens, marshes, and estuaries)." Different wetland types arise due to a few key factors, primarily: water levels, fertility, natural disturbance and salinity. Around Lake Pontchartrain, for example, these few factors produce wetlands including bottomland hardwoods, cypress swamp, freshwater marsh and brackish marsh. High levels of flooding reduce the abundance of trees, leaving four principal marsh types: saline, brackish, intermediate and fresh. Although these areas make up a very small percentage of the total land found in the United States, southern Louisiana contains 40 to 45 percent of the wetlands found in the lower states. This is because Louisiana is the drainage gateway to the Gulf of Mexico for the Lower Mississippi Regional Watershed. The Lower Mississippi Regional Watershed drains more than 24 million acres (97,000 km2) in seven states from southern Illinois to the Gulf of Mexico. Hence the wetlands of this area are important at the national scale. On the east side of Louisiana, coastal wetlands intergrade with long leaf pine savannas, which support many rare and unusual species such as pitcher plants and gopher tortoises. On the western side, they intergrade with wet prairies, an ecosystem type that was once vast, and now has been all but eliminated. The larger vertebrate fauna such as wolves and bison was exterminated. The eastern coastline of Louisiana is much more susceptible to erosion than the western coastline because much of the eastern coastline was created by silt deposits from the Mississippi River. This