Kudzu, red clover, pigs, blood red shrimp and water hyacinth are some of the most familiar of the over 6500 “invasive species” that have taken up residence here. There are many many known benefits these plants and fish have brought with them. Kudzu for soil erosion is also a great nutrient consolidator, same goes for clover, pigs have become about as American as apple pie (for better or for worse), the blood red shrimp is a delicious freshwater fish that could help with marine fish shortages and the future of inland aquaculture. Water hyacinthg is a waste water treatment plant, like duckweed and also holds promise as a biofuel.
This article from National Center for Public Policy Research gives a good summary of the issues:
“The zebra mussel, for example, is one of the most feared “invasives,” referenced in almost any article on exotic species and the purported raison d’etre for numerous bills pending in the U.S. Congress and state legislatures. The tiny mollusk inhabits fresh water lakes and rivers and is infamous for clogging industrial plant water pipes, particularly in the Great Lakes and Mississippi Basin, where they have exploded on the scene. Believed by scientists to have been brought over from Europe in ships’ ballast waters, some observers claim these hardy, prolific shell-fish could wipe out native aquatic life, though there is no conclusive evidence to support this theory.
Rarely reported is the zebra mussel’s positive effect on water quality. These “filter feeders” eat algae and fertilizer runoff from lakes and, as a result, waters they populate are frequently clear and free of pollution. As reported by the U.S. Geological Survey:
“…there has been a striking difference in water clarity improving dramatically in Lake Erie, sometimes four to six times what it was before the arrival of zebra mussels. With this increase in water clarity, more light is able to penetrate deeper allowing for an increase in aquatic plants. Some of these macrophyte beds have not been seen for many decades due to changing conditions of the lake mostly due to pollution. The macrophyte beds that have returned are providing cover and acting as nurseries for some species of fish.”18
The plant purple loosestrife, maligned for crowding out natural wetlands vegetation and wildlife, has been called everything from “the poster child” for invasive species19 to the “purple plague.”20 Yet there is no scientific evidence that the plant causes actual displacement in the life cycle of native flora or fauna.21 Moreover, some biologists acknowledge actual benefits, including the plant’s ability to absorb nitrogen and phosphorus from the water better than even cattails and to help prevent soil erosion.22
Similarly, the South American water hyacinth blankets lakes and ponds in tropical climates, halting boat activity and, some claim, depleting aquatic life by blocking sunlight and crowding out native plant life. But the plant also has a newly discovered talent – it eats raw sewage. The alien species is used by a growing number of sewage treatment plants around the country23 to help purify water and performs the job at a fraction of the cost of conventional methods. NASA, which is researching the new-found technology, planted water hyacinth over 40 acres of sewage lagoons and reports: “The plants flourished on the sewage and the once-noxious test area became a clean aquatic flower garden.” They are also being researched for fertilizer, animal feed and biofuel.”