Threats to the Park
Many non-native species have set up residence in Great Smoky Mountains National Park. A non-native is any species that occurs outside its native range as a result of deliberate or accidental introduction by humans. Non-natives compete with native species for habitat and food and often take over specialized ecosystems that rare plants or animals need to survive. The non-native species are not natural components of the ecological system and, as a result, have not evolved in concert with the native species.
Wild coyote in Cades Cove by Sam McDonald
Often, non-native species will not have natural predators, so their numbers will grow alarmingly. In fact, most of the successful non-natives seem to be pre-adapted to our area. This could be explained by the biological similarity between the Smokies and regions of Europe, East Asia, and western North America. The presence of non-native species in the Smokies is a detriment to the park as an International Biosphere Reserve because of the reduction in biological diversity as native populations are forced out of their environmental niches.
Rooting and wallowing wild hogs (Sus scrofa) threaten natural ecological communities. The hogs will eat just about anything, including Red-cheeked Salamanders (Plethodon jordani), which are found only in the park, and the roots and foliage of wildflowers that often take years to mature and bloom. They also damage wetlands and springs, creating disturbances that encourage invasion by non-native plants.
Balsam Wooly Adelgid and Hemlock Wooly Adelgid
The balsam woolly adelgid (Adelges piceae) is an insect pest that infests and kills stands of Fraser fir trees (Abies fraseri) in the spruce-fir zone. This fir occurs naturally only in the southern Appalachians and used to be the dominant tree at the highest elevations. The adelgid was accidentally introduced on trees imported from Europe, and the fir has little natural defense against it. By injecting the tree with toxins, the adelgid blocks the path of nutrients through the tree causing a slow death.
A close relative of the balsam woolly adelgid, the hemlock woolly adelgid has devastated a majority of hemlock trees in the Great Smokies. The hemlock woolly adelgid is native to Asia and was first discovered in the eastern United States in the early 1950s. It has the potential to kill all or nearly all the hemlock trees in the Southern mountains, an area with thousands of acres of virgin hemlock forest.
The National Park Service is fighting the hemlock adelgid with insecticidal soaps, ground treatments, and by releasing a tiny predator beetle with a voracious appetite for adelgids. Over 60 hemlock conservation areas of between five and 20 acres have been established in the park. Every hemlock in these special areas is treated with pesticide either by soil drench or trunk injection. In addition, nearly all hemlocks in campgrounds, picnic areas, along roadsides, and near backcountry campsites have been treated. Still, over the long term, predator beetles and other biological controls are the best hope for widespread protection of this ecologically critical tree species.
Rainbow and Brown Trout
Rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) offer stiff competition for the native brook trout (Salvelinus fontinalis). Imported from the West during the logging era in the early 1900s, rainbow trout were brought to “improve” the fishing in the mountains. Originally from Germany, the brown trout came into the park from stocked boundary streams. Larger and more aggressive than the native brook trout, these non-native species compete with the brook trout for food and force them into less desirable habitats.
There are also over 380 species of non-native plants in Great Smoky Mountains National Park, including kudzu (Pueraria montana), mimosa (Albizia julibrissin), and Oriental bittersweet (Celastrus orbiculatus). Many of these species are found in sites that have undergone recent disturbance. Once established, they are aggressive competitors with native plants and can change natural succession. Other problems caused by non-native plants include interbreeding with closely related native species and out-competing rare native plants that require specialized habitats.
National Park Service policy states that manipulation of populations of non-native plant and animal species, up to and including total eradication, will be undertaken whenever such species threaten the resources being preserved in the park. Great Smoky Mountains National Park is following this policy as long as the programs to control non-native species do not result in significant damage to native species, natural ecological communities or processes, or historic objects.
Management procedures vary for the non-native species mentioned above. The park is trying to totally eradicate some non-native plant species through the use of herbicides that do not harm the ecosystem. The balsam woolly adelgid problem is being dealt with through an insecticidal soap that kills the insect, but is non-toxic to most other organisms and breaks down quickly in the environment. Aerial spraying is ineffective, so each tree must be sprayed individually. This is a very time consuming and expensive process, and only a small part of the total fir population can be protected.
The story is quite different for non-native trout and wild hogs. The park stopped stocking rainbow trout in 1975, and fishing is allowed for both rainbow and brown trout. Current management efforts include the removal of non-native trout species from streams where they are mixed with the native species. Natural barriers, such as waterfalls, are being used
to separate brook trout populations from rainbow and brown trout.
So far the most effective method of hog management is a combination of trapping and shooting. A rooting survey is taken in the park to determine the distribution of hogs, and vegetation monitoring is performed in hog exclosures. Exclosures were once sites of hog disturbance, but are now fenced to exclude the hogs. They give researchers the opportunity to monitor what happens to both the plant and animal life in an ecosystem once the non-native species has been excluded.
It may be impossible to completely eradicate all non- native plants and animals from the Great Smoky Mountains. And even if eradication were possible, re-infestation would likely occur from areas outside the park. Still, park managers are successfully controlling populations of most non-natives to the extent that the park’s native flora and fauna, some of which is endemic to the region or unique to the park, has the habitat necessary for survival.