WETLAND DAMAGE

In 1998, the first coast wide nutria herbivory survey was flown, as part of the Nutria Harvest and Wetland Demonstration Program. A total of 23,960 acres of damaged wetlands were located at 170 sites along the survey transects. In 1999, the damaged increased to 27,356 acres located at 150 sites. In 2000, the damage slightly decreased to 25,939 located at 132 sites. In 2001, the damage decreased to 22,139 acres located at 124 sites. In the 2002 survey, the damage decreased again, but only slightly to 21,185 acres located at 94 sites. The survey completed in June 2003 resulted in 84 damage sites covering a total of 21,888 acres. The survey completed in May 2004 showed 69 damage sites covering 16,906 acres. The survey, completed in May 2005, showed 49 nutria damage sites covering 14,260 acres. In May of 2006, the survey showed 31 nutria damage sites covering 12,315 acres. The most recent survey completed in May 2007 reported 23 nutria damage sites, totaling 9,244 acres.  When extrapolated to a coastwide estimate, the acres impacted over these years ranges from 102,585 to 34,665 acres (damaged acres x 3.75). The 3.75 multiplication factor comes from the area actually surveyed along transect lines (0.5 miles) and the distance between transect lines (1.87 miles).

Vegetative damage caused by nutria has been documented in at least 11 Coastal Wetlands Planning Protection and Restoration Act (CWPPRA) project sites in the Barataria-Terrebonne Basins. The estimate of 80,000 acres of marsh damaged was conservative because only the worse (most obvious) can be detected from aerial surveys. The number of acres being impacted was certainly higher. Since the introduction of the Coastwide Nutria Control Program, the number of impacted acres has dropped to 34,665 acres. When vegetation is removed from the surface of the marsh, as a result of over grazing by nutria, the very fragile organic soils are exposed to erosion through tidal action. If damaged areas do not revegetate quickly, they will become open water as tidal scour removes soil and thus lowers elevation. Frequently the plant's root systems are also damaged, making recovery through vegetative regeneration very slow.

Click below on images to see wetland damage caused by nutria.