Invasive Species

Invasive species are those that are not native to the place that they are in and are also causing a problem for the native species. Millions of acres of land in the United States are covered by invasive species.¹¹ They have taken over many of the natural lands in the U.S. both privately and publicly owned, all across the country. There are hundreds of invasive species in the U.S. and an even higher number of non-native species.¹¹

Some of the invasive species in the U.S.

Plant, animal, and even microbes can be invasive. Not every species that is transported to the U.S. becomes invasive, just species that have the opportunity and adaptations to compete with native species for food, water, light, and other resources.² Species may live for several years before having the opportunity to cause a problem. 
Some of the problems that invasive species cause are destruction of native habitat, decrease diversity, and replace native species.¹¹ All of this costs the government and private citizens millions of dollars. 
Invasive species are brought over by many different ways, including for agriculture, pets, decoration, or for zoos.¹¹ They can also be transported accidentally on planes, boats, or on people. With so many people and vehicles travelling internationally it is very difficult to prevent all accidental transfers of plants and animals.

A sign to warn boaters about invasive species

It is very difficult for anyone to guess what species will become invasive and which won't because of many different factors effect how the species will fit into the new ecosystem. Sometimes a disturbance like a fire, flood, or disease needs to happen before an exotic species becomes invasive.