Protecting Native from Invasive Species

Invasion of natural habitats by nonnative species contributes to biodiversity loss and extinctions. Native species consist of plants or animals that normally thrive in a particular community. Invasive species, by contrast, do not naturally belong in the environment they invade; they are also called nonnative, alien, or foreign species. Introduced species are those that have been deliberately or accidentally released in a new, nonnative environment. Exotic species also arrive deliberately or accidentally, but these species tend to be rare, unique, and highly valued. An orchid known to grow only in Brazil would be an exotic species in Connecticut for instance. By any name, these plants and animals oft en create biological havoc in the community they invade. Th is invasion of new habitats can occur by three diff erent means: migration, deliberate introduction, and accidental introduction.

Invasive species threaten native species by crowding the native populations out of their space and using up their water and food sources. Th ey do this by outcompeting the native species in the natives’ own habitat, perhaps aided by any foreign parasites that the invader also brings into the community. In many cases, the native species have no defenses against an unfamiliar pathogen or parasite, and their numbers plunge due to disease.

Invasion’s main threat to biodiversity resides in ecosystem imbalance, in which normal food webs and other interrelationships cannot work because one or more of the ecosystem’s components have been eliminated. Native species in invaded habitats disappear for the following reasons: forced migrations to new areas, disease, starvation, and unnatural behaviors. Behavioral changes often include conflicts between native animals and the invader, or against other members of the same species. Invaders usually bring aggressive mannerisms with them into their new territory, and, as a consequence, native species can offer little resistance to the takeover.