An exotic species, also called a non-native species, an introduced species or an alien species, is a species of organism that is not native to an area. The presence of an exotic species can have little or no effect on an ecosystem, or it can have a large effect, and the effect can be either harmful or beneficial. An invasive species is an exotic species that is harmful because it causes disruption in its new habitat, including reducing or eliminating existing species by consuming them or outcompeting them and reducing or eliminating species that have depended on existing species.
Exotic species can be introduced to an area naturally, but they are increasingly being introduced by humans, both accidentally and deliberately. They have been introduced unintentionally by being carried accidentally on transportation vehicles, such as airplanes, ships, trucks and automobiles, including on the items that they transport. Reasons that they have been introduced intentionally include for economic gain, to make a product available locally, and as a biological control.
One of the most destructive examples of an exotic species is the cane toad, which was purposely introduced into Australia and a number of other sugar-growing countries in the first half of the twentieth century in an attempt to control the beetles that consumed the roots of sugar cane plants. Another example is kudzu, which was introduced to the southern U.S. from Japan more than a century ago as an ornamental plant but has spread uncontrollably and is destroying much native vegetation as well as damaging buildings and electric power lines.