Defenders' Experts
Invasives Species: Enemies at the Gate
A sampling of the species that haven’t gotten a foothold here...yet.
Brown tree snake – this Asian species has infested the American territory of Guam, where it has "single-mouthedly" wiped out nine of that island’s native bird species. They also have painful bites and cause power outages by climbing onto the power lines. To protect its own bird populations (already decimated by other exotic species), Hawaii’s Department of Agriculture considers it a priority to keep the snakes out, and now inspects every plane that arrives from Guam. Six snakes have been intercepted, having climbed into the wheel-wells of planes, and dozens more have been found on planes in Guam prior to takeoff. Since a female can produce offspring for seven years following mating, it might only take a single oversight to cause a disaster.
Asian gypsy moth – a relative of the European gypsy moth, this species entered the country in the early 1990s in a shipment of grain. A massive effort by federal and state agencies apparently wiped them all out, but the consequences of an invasion would be dire: unlike its European cousin, the Asian gypsy moth defoliates conifers in addition to hardwoods, and could spread more rapidly because the females can fly.
Northern Snakehead – an air-breathing, land-crawling fish native to China, the northern snakehead can slither to another river or pond to find new food sources, surviving up to three days out of water. This fish, which preys on other fish, frogs, aquatic birds and small mammals, was recently found in a pond in Maryland, where it was dumped after it grew too large for a collector’s aquarium. Fearing that the snakehead would spread to nearby rivers and potentially disrupt food chains and ecosystems in water systems throughout the Northeast, wildlife authorities were forced to poison the pond to ensure that all specimens were eliminated. After dredging the pond, authorities found seven adults and thousands of offspring.
Foot and mouth disease – This debilitating disease of ungulates has ravaged the livestock and rural tourism industries in Britain. It is highly contagious, and if it reaches the U.S. again (an outbreak here in the early part of the 20th century was contained), it could spell disaster for native deer, elk, moose, and the predators that depend on them, as well as for the livestock industry.
As these species and their potential effects demonstrate, it is critically important to maintain efforts to keep out potential new invaders, and to support efforts to quickly control new infestations while it is still possible to do so.
A sampling of those species that have.
Asian Longhorned Beetle – a native of northeast Asia, particularly areas of China and Taiwan, this white-spotted beetle was introduced into the U.S. in 1996 through untreated wooden packing materials from China. Although restrictions on such packing materials were introduced in 1998, the insect continues to cause extensive damage with more recent appearances in New York, Chicago and Oregon. The beetle attacks hardwoods, such as maple, horsechestnut and poplar, by burrowing into trees to deposit larvae which then weaken the tree’s immune systems. Further infestation presents a significant threat to timber, nursery stock, maple syrup and recreation industries, which generate on average $11 billion in New York state and $138 billion nationwide.
Kudzu – a semiwoody vine, with a twining and trailing growth habit, kudzu was brought to the U.S. in the early 1900s for use as a soil stabilizer, ornamental vine and animal fodder. Kudzu forms dense infestations covering ground and trees, thereby out-competing native plant species. Kudzu is prevalent throughout the Southeastern U.S., with particularly heavy concentrations in Alabama, Georgia and Mississippi. It is reported to infest about 2 to 3 million hectares and results in estimated loses of $500 million per year in land productivity and control costs.
Zebra Mussel – native to the Caspian and Black Seas, Zebra Mussels are established in Western Europe, Canada and the U.S.. In the U.S., these mussels were introduced in the mid-1980s through the release of ballast water from foreign ships, and are now are found throughout the Great Lakes area and more recently along the East coast. They compete with zooplankton for food, thus affecting natural food webs, and also interfere with the ecological functions of native mollusks. Additionally, zebra mussels can clog the piping and mechanical systems of industrial plants, power utilities, locks and dams, as well as damage boat hulls and engines. Furthermore, the mussel is easily transported on boats, trailers and other recreational watercraft, which are used in different bodies of water.
For more examples download the Invasive Species Gallery.
|
|
