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Invasive Plants
Questions and Answers
What is an invasive species?
The U.S. government defines an invasive species as one "that is not native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health."
The multiflora rose is lovely looking, but its rampant spread has made it an outlaw in several states.
How do plants become invasive?
Simple physics dictates that two plants cannot occupy the same spot, so when a nonnative plant settles into a new ecosystem, it displaces a native. Invasive plants may grow faster, taller, or wider and shade out native species. Many stay green later into the season or leaf out earlier, giving them an advantage over natives. Nonnative plants can change the vertical and horizontal structure of ecosystems, alter hydrology, and disrupt nutrient cycles—all with devastating effects on native plants and animals.
How much damage do invasive species cause?
According to a paper by Cornell ecologist David Pimentel and others, invasive species cause major environmental damage amounting to almost $120 billion per year. About 42 percent of the species on the U.S. List of Endangered and Threatened Species are at risk primarily because of nonnative invasives. (See Ecological Economics, Volume 52, Issue 3, 1 February 2005, pages 273–288.)
Is it possible to predict whether a plant will be invasive?
A foolproof system for predicting invasiveness has proven elusive, but a few traits should raise red flags. For example, nonnative species bearing fleshy fruits dispersed by birds are at the top of the suspect list. Declining to plant—or recommend—such species can help prevent plant invasion. However, the most prudent prevention measure is to choose a regionally native species.