Nutria fur has never been very popular, much less so today. At 50 cents or less a pelt, it's just not worth trapping them. So the population, in the absence of any native predators, quickly overwhelmed the less competitive muskrat, and took over the Louisiana swamps. A park the size of Jean Lafitte may contain several hundred thousand of the hungry rodents, and they have a special fondness for the tender young buds of baby cypress trees. Because of their appetite, they may prevent the cypress trees from regenerating, and when the existing trees die out, the swamps will disappear.
Invertebrates do much better in the swamp than vertebrates.
Oligochaete worms, clams, snails, shrimp, insects, and crawfish are among the large community of annelids, molluscs, and arthropods that live in swamps. The basis of the invertebrate food chain in the swamp is the detritus, or leaf litter that covers the floor of the swamp. This litter supports a thriving community of detritivores, organisms that feed on detritus, particles of dead and decaying organic matter. In addition to providing valuable habitat for numerous species, freshwater wetlands also act as filters to remove excess nutrients and toxic pollutants from the water. They are tremendous filters for human sewage, toxic metals, and other types of pollutants.