What Invasive Species Are

An exotic, or alien, species is any life
form that enters an ecosystem
outside of its normal range. Humans
play a major role in the transportation
of invasive species due to the
increasing global traffic of people
and goods. The sheer volume of
commerce being moved around the
globe is so great that many more
species can be transported than in
the past. Advances in technology have decreased the transportation time involved, so invaders have a better chance of surviving the trip. Invasive species can be both plant and animal, living on land (terrestrial) or in the water (aquatic). There have been many beneficial exotic species introduced to the United States, such as most of the agricultural crops we grow today.

However, an invasive species is an exotic species that can severely alter the habitat it is introduced into. These are the species of great concern to the National Park Service. Some of the more common terms used to describe invasive species are: weeds (for plants), noxious species, nuisance species, and non-indigenous species.