Introduced Species

The Global Water Crisis

What Are Introduced Species?

Introduced species are species that now live outside of their native range. These species are introduced to new areas–usually over previously inaccessible bodies of water–by human activity, either deliberately or accidentally. The Environmental Protection Agency defines introduced species as “species that have become able to survive and reproduce outside the habitats where they evolved or spread naturally.”

The Terminology of Introduced Species

Scientists are ambivalent about introducing species to areas that they don’t naturally inhabit. Introduced species are introduced to these new areas by accidental or deliberate human activity. Introduced species can harm the ecosystems of the places that they’re introduced to. However, sometimes introduced species can have no effect on or even help the ecosystems they’re introduced to. For instance, some of the plants that Europeans brought into North America have aided the continent’s biodiversity and productivity. Because introduced species can spread too quickly for us to control and can sometimes help us, most environmentalists consider it impractical and undesirable to simply prohibit introducing non-native species.

How We Refer to Introduced Species

Scientists refer to introduced species by many terms, like “non-indigenous,” “non-native,” “exotic,” and even “invasive.” The broadest term applied to introduced species is “non-native,” which can be applied to both agriculturally maintained and wild species. Some introduced species can survive by themselves in nature when introduced—these are “naturalized” species. “Invasive” species threaten ecosystems by spreading or reproducing too widely or too fast, thereby harming the environment or human health.

How We Introduce Species: Intentionally Introduced Species

Through human activity, we introduce species to places that they don’t naturally inhabit. Sometimes we introduce species accidentally, and sometimes intentionally. People usually introduce species intentionally because they will economically gain by doing so. For instance, New Zealand introduced the Monterey Pine to bolster timber crops. We have also introduced species for recreational activities, like game hunting or ornamental gardening. We have also introduced species by bringing pets overseas. When we try to establish introduce these species in the wild, we often have trouble predicting how well the introduced species will fare. For this reason, we often have to make several attempts to establish an introduced species.

Accidentally Introduced Species

Sometimes people accidentally introduce species to new areas. For example, we have spread many rat species spread across the world by unintentionally transporting them aboard ships. Human travel also introduces several species to places where they don’t naturally inhabit. For example, tourists introduced the African killer bee to Brazil.