One of the largest peripheral issues I came across in researching my book on cormorants was the introduction of non-native marine and aquatic species into already stressed ecosystems. It happens all over the world, usually as a result of careless or illegal ballast dumping by commercial shipping. These invasive species sometimes enter the system through intentional introduction, as attempts to rectify perceived economic or environmental failures.
One current species in the news is the Silver Carp, introduced into the United States – Arkansas -- in 1973. As a plankton feeder, planners thought silver carp could clean up clogged waters by purging them of overabundant phytoplankton. It was also thought to be a possible food fish. Between releases and escapes these fish spread through many states via numerous river systems. With few or no predators silver carp overpowered native species in their numbers. And as filter feeders, in addition to clearing the phytoplankton, the carp consumed the floating larvae and juveniles of many native species.
Silver carp, besides out-competing the natives, exhibit a unique behavior in the presence of running boat engines. They jump – by the hundreds – bashing boat windshields and boaters alike moving through their waters. Right now the carp are on the verge of entering the Great Lakes system and threatening those inland seas fisheries, perhaps to a degree of that may not be recoverable.
A simple action intended as a simple remedy, again. President U.S. Grant tried essentially the same scheme about a hundred years ago, after the Civil War, in an attempt to feed and nurture the county’s growing cities. He ordered his newly formed Fish Commission to find a fish that might be cultivated as a food source and might be useful in clearing choked algae-clogged waterways. Asian carp, in a number of varieties, filled the bill. They were imported, then released and escaped into waterways and eventually made their way throughout the country. Instead of clearing rivers and lakes carp managed to darken and stain the waters with silt and mud as they rooted into the bottoms searching for food. As far as being a food fish went, they found their way onto dinner tables and restaurant menus for a time, but lost favor as the saltwater fisheries grew with the emergence of refrigerated railroad cars.
Today, we live with the destructive Asian carp. In four-foot sizes, they are found nearly everywhere, except as common dinner fare and on restaurant menus. An exotic less than exotic now and a lesson not learned.
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So true--unfortunately this problem is not limited to the marine world. Norway Maple was brought here from, you guessed it, because it was a lovely tree in its very cold, native habitat. Here it has become a nuisance tree, producing thousands and thousands of seedlings from every tree. Take a walk in the woods--there you'll see plenty of other examples of invasive species, introduced to "improve" American gardens: mile-a-minute weed, multiflora rose, Japanese honeysuckle, Oriental bittersweet, autumn olive. As Dr. Tallamy points out in his book, Bringing Nature Home, not only are these plants invasive, choking out native plants, but they might as well be styrofoam to the native insects; they can't eat this stuff! And without insects, there are no ... You name it. A pretty scary scenario.
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