nutria, and therefore for reduced impacts of grazing. Southern Louisiana's disappearing wetlands have a broad impact ranging from cultural to economic. Commercial fishing in Louisiana accounts for more than 300 million dollars of the state's economy. More than 70% of that amount stems from species such as shrimp, oysters and blue crabs that count on the coastal wetlands as a nursery for their young. Annually Louisiana sells more than 330,000 hunting licenses and 900,000 fishing licenses to men and women who depend on the wetlands as a habitat for their game. Additional recreational activities such as boating, swimming, camping, hiking, birding, photography and painting are abundant in wetland areas. Wetlands host a variety of trees such as the bald cypress, tupelo gum and cottonwood. Other plants such as the dwarf palmetto and wax myrtle and submerged aquatic plants such as Vallisneria and Ruppia are native to Louisiana wetlands. Wetland plants act as natural filters, helping to remove heavy metals, sewage, and pesticides from polluted water before reaching the Gulf of Mexico. Animal species native to these areas include osprey, anhinga, ibis, herons, egrets, manatees, alligators, and beavers. Although there are several naturally occurring forces that adversely affect the wetland regions of Louisiana, many believe it is human intervention that has caused the majority of the decline. Prior to the building of levees on the Mississippi River, the wetlands were kept in balance by occasional floods, which fill the area with sediment, and subsidence, the sinking of land. After the levees were built, however, flood sediment flowed directly into the Gulf of Mexico. This subsidence along with the recent sea level rise tipped the balance toward subsidence rather than marsh growth. This, along with the canals built in the area, caused decline of the wetlands and also caused less weakening of and less protection from recent hurricanes such as Hurricane Katrina. The Lake Pontchartrain Basin Foundation has developed a comprehensive management plan for the eastern regions of the Louisiana coast, placing emphasis upon restoration of river habitats, cypress swamps and fringing marsh. This could be a model applied to other coastal regions. Oil company canals The dredging of access canals by oil companies has long been considered to be a cause of coastal erosion. These concerns were raised in 1925 and continued with a 2013 lawsuit against many oil companies. Policy and protection The National Oceanic and Atmospheric Administration (NOAA) enacted