II. Invasive Species
June 12 2008
Part 2 of Four major threats to America's forests and grasslands
The term invasive species is generally used in a negative sense to describe species that are introduced into an area in which they are not of native origin. The introduction of non-native species tends to have a disruptive effect upon the ecosystem. This is not always the case when non-native species are introduced, however, in some instances, the invading species may be lacking in natural predators or pests and so in the new environment may overwhelm or eliminate native species.
A notorious example of an invasive, non-native species is the Kudzu vine, which was first introduced at the 1876 World's Fair held in Philadelphia as an ornamental and also as a forage crop (to feed animals). For many years kudzu was planted widely in the southeast to combat soil erosion. It's revealed itself as an unwieldly nuisance and has been abandoned by most as a method of erosion control.
Crown vetch is still used by states to combat erosion control despite drawbacks due to its aggressiveness. Pennsylvania has officially declared it the “state beautification plant”. Admittedly, it's a beautiful plant but it's prolific spread can be devastating to native species and therefore, is a detriment to North American ecosystems.
The zebra mussel is another example of a harmful invasive species. The zebra mussel tends to crowd out other mussels and become a nuisance, clogging up pipes and drains. It was first introduced into the Great Lakes as a stowaway in the ballast water of a transoceanic ship from Eurasia in the mid 1980s. It's now found in many large water bodies in the U.S. and Canada.
The fire ant is an aggressive, multiple biter with painful venom. They may damage fruits, berries and crops; and even electric boxes. Ant mounds are a hazard to farm equipment.
The invasive Japanese Stiltgrass is especially well-adapted to low-light conditions, therefore it may spread to blanket forest floors, crowding out sensitive native species. In well-lit open spaces, by avoiding it, white-tailed deer may inadvertantly encourage its dominance over their preferred native plants.
These species may all have their positive points but out of their natural element, require monitoring and control in order to conserve local ecosystems.
Internet Resources:
Invasive Plants of the Eastern United States: Identification and Control
The Tennessee Exotic Plant Management Manual
TWRA Invasive/exotic Aquatic Species
