Shenandoah National Park contains a host of nonnative animal and plant species. Indeed, for vegetation alone there are 350 nonnative plants, about 25% of the total. "Exotic," "alien," "introduced," "non-indigenous," and "nonnative" are all synonyms for species that humans intentionally or unintentionally introduced into an area outside of a species' natural range.
Nonnatives were introduced with the earliest European immigrants, but new introductions continue today. Purposeful introductions were for game management, wildlife habitat enhancement, industrial development, soil erosion protection, or just to remind settlers of their first homes far away, among other reasons. Accidental introductions have been through unintended releases and biological hitchhiking on vehicles, personal effects or trade goods.
While many nonnative species have minimal or even beneficial impact on recipient sites, some are more problematic. These invasive nonnative species are among the most serious threats that parks face today. Invasive nonnatives disrupt complex native ecological communities, jeopardize endangered native plants and animals, and degrade native habitats. Hybridization with exotics alters the genetic integrity of native species. Of the 350 nonnative plants in Shenandoah, roughly 35 (10%) are considered problematic invasive species. If invasive nonnatives are not actively and aggressively managed, the National Park System is at risk of losing a significant portion of its biological resources.
Examples of invasive nonnatives found at Shenandoah include:
National Park Service policy on nonnative species directs that they be managed if their presence threatens natural or cultural resources, or human health or safety, and if control if feasible. Executive Order #13112 on Invasive Species instructs all non-defense agencies to control invasive nonnative and not permit new infestations. Though it is not humanly possible to eliminate all invasive nonnative species at this time, the Park is engaged in a number of strategic actions including inventory, control, monitoring, and site restoration.
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