Shenandoah National Park - Non-native Species (U.S. National Park Service)

Mile-a-minute Vine

Shenandoah National Park contains a host of non-native animal and plant species. Indeed, for vegetation alone there are 300 non-native plants, about 23% of the total. "Exotic," "alien," "introduced," "non-indigenous," and "non-native" are all synonyms for species that humans intentionally or unintentionally introduced into an area outside of a species' natural range. The invasion of non-native species is one of the most serious threats that parks face today. Non-natives 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. In some cases, non-natives are also regarded as pests because they cause human health and annoyance problems. If non-natives are not actively and aggressively managed, the National Park System is at risk of losing a significant portion of its biological resources.

Non-natives 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.

Examples of non-natives found at Shenandoah include:

Gypsy moths were brought to this country in 1869 for genetic crosses to create a more productive silkworm. It was accidentally released near Boston, Massachusetts. Millions of trees died in the Park during the epidemic of 1986-95.
Hemlock woolly adelgids were accidentally introduced into this country on imported hemlock nursery stock. The insect has killed thousands of hemlocks in the Park, destroying valuable shaded riparian habitat along streams and springs.
European starlings were introduced into the country in the late 1880s. They are known to compete with native cavity nesting birds and have documented ill effects upon northern flickers and redheaded woodpeckers. Starlings are commonly seen at Big Meadows.
Kudzu vine was originally brought to America in 1876 to decorate house arbors. It was later used in the U.S. to control erosion along highways. It now covers millions of acres in the South. The Park has a small infestation it controls along its eastern border.
Tree of heaven was brought into this country in the 1780s for arboretum plantings. It escaped to dominate mid-Atlantic forest edges and openings. The Park has hundreds of infested acres.

National Park Service policy on non-native species recommends that they be considered for full eradication efforts to preserve native species and ecosystems. Executive Order #13112 on Invasive Species instructs all non-defense agencies to control aliens and not permit new infestations. Though it is not humanly possible to eliminate all non-native species at this time, the Park is engaged in a number of strategic actions including inventory, control, monitoring, and site restoration.

Related Information

Useful references that deal with non-native species are:

USDI-NPS. 1997. Exotic Species in the National Park Service.Fact sheet 97-7, January 1997. USDI-National Park Service, Natural Resource Information Division. Washington, DC. 1pp.

USDA-FS. 1991. Hemlock woolly adelgid. Pest Alert NA-PR-06-91. USDA- Forest Service, Northeastern Area. Morgantown, West Virginia. 1 pp.

USDA-FS. 1989. Gypsy moth. Forest Insect & Disease Leaflet 162, Revised October 1989. USDA-Forest Service, Washington, DC. 13 pp.

A website that provides helpful information about non-native species is:

Gateway to Federal and State Invasive Species Programs

Listing of these websites does not and is not intended to imply endorsement by the National Park Service of commercial services or products associated with the sites.