When is a Non-native Species Considered Invasive?It is often thought that the terms 'invasive' and 'non-native' can be used interchangeably, but this is not always the case. A species is deemed invasive only when it causes harm to the environment, economy, or human health. The mere fact that a species is non-native does not automatically raise concern as many non-natives do not disrupt or threaten the survival of other native organisms. The National Park Service manages species that are harmful and classifies them as invasive. Impacts of invasivesInvasive species in the Smokies compete with native species for things like habitat and food, taking over specialized ecosystems that native species need to survive. Invasive species are not natural components of local ecological systems and have not evolved alongside native species. Often, invasive species lack natural predators, allowing their populations to grow at an alarming rate. Many are 'pre-adapted' to local conditions, possessing traits like climate resilience, rapid reproduction, and the ability to effectively use available resources, which give them a competitive advantage over native species. The presence of invasive species in the Smokies poses a significant threat to the park as an International Biosphere Reserve, as native species may be negatively impacted. 
W. Bielenberg Some Species that Threaten the SmokiesHemlock Woolly AdelgidThe hemlock woolly adelgid (HWA) (Adelges tsugae) is an invasive insect from Asia that has devastated eastern hemlock tree (Tsuga canadensis) populations in Great Smoky Mountains National Park. Since its detection in the park in 2002, it has caused significant declines in eastern hemlock stands. Eastern hemlock trees are crucial to the health of ecosystems in the Smokies, providing critical habitat for a variety of plant and animal species. Their dense canopies help regulate both air and water temperatures, creating beneficial conditions for aquatic life, such as native brook trout, eastern hellbenders, and numerous species of aqautic insects. Additionally, eastern hemlocks play a significant role in soil stabilization, water retention, and water quality by reducing erosion and maintaining watershed health. Balsam Woolly AdelgidThe balsam woolly adelgid (Adelges piceae) is an invasive insect that has severely impacted Fraser fir populations in Great Smoky Mountains National Park. Introduced from Europe, it feeds on the sap of fir trees, injecting toxins that disrupt nutrient flow. Since its arrival in the park in the 1960s, it has caused widespread die-offs, especially at high elevations like Kuwohi. The loss of Fraser firs has altered forest ecosystems, affecting species that rely on these trees for habitat and food, such as the spruce-fir moss spider, northern flying squirrels, and many species of salamanders. Annual monitoring in 2024 showed that balsam woolly adelgid densities on Fraser fir trees remained low at four mountaintop monitoring sites, while fir saplings along the Kuwohi Trail thrived. Foresters believe that these ecosystems may exhibit signs of resilience, attributed to improved air quality, cleaner soil from reduced acid rain contaminants, and genetic resistance. Younger fir trees typically show greater resilience than older ones; however, the definitive outcome will only be determined over time. Spongy MothThe spongy moth (Lymantria dispar), formerly known as the gypsy moth, is an invasive insect that poses a threat to hardwood forests in Great Smoky Mountains National Park. It feeds on the leaves of oak and other broadleaf trees, causing defoliation that weakens the trees and increases their vulnerability to disease and other pests. Although not yet widespread in the park, foresters actively monitor for the moth and use traps and targeted treatments to manage its spread. In 2024, several traps in the Elkmont area of the park detected spongy moths. Continued vigilance is necessary to protect the park’s diverse forest ecosystems. 
Leah Bauer Emerald Ash BorerThe emerald ash borer (Agrilus planipennis), an invasive beetle from Asia, was first discovered in Great Smoky Mountains National Park in 2013. It threatens the park’s native white and green ash trees by burrowing under the bark and disrupting nutrient flow, eventually killing the trees. Asian Long-Horned BeetleThe Asian long-horned beetle (Anoplophora glabripennis) is an invasive species that poses a significant threat to hardwood trees but has not yet been detected in Great Smoky Mountains National Park. Native to Asia, this beetle attacks and kills a variety of tree species by boring into the wood and disrupting nutrient flow. Park foresters conduct regular surveys and engage in outreach efforts to prevent the introduction of the species and to help identify any infestations. Spotted LanternflyThe spotted lanternfly (Lycorma delicatula), an invasive insect native to Asia, poses a significant threat to the ecosystems of Great Smoky Mountains National Park. It feeds on the sap of more than 70 plant species, weakening trees and making them more vulnerable to disease. Although it has not yet been confirmed in the park, officials are on high alert due to its rapid spread in surrounding regions. Efforts are underway to monitor and prevent its introduction through public awareness and early detection programs. 
Meredith Boatman Wild HogsWild hogs (Sus scrofa) can have significant impacts on natural ecological communities through their rooting and wallowing behavior. These adaptable foragers consume almost anything, including red-cheeked salamanders (Plethodon jordani)—a species unique to the park—and the roots and foliage of wildflowers, which require years to grow and bloom. Rainbow TroutRainbow trout (Oncorhynchus mykiss) pose stiff competition for the native brook trout (Salvelinus fontinalis). Imported from the western U.S. during the logging era in the early 1900s, rainbow trout were brought into the park to increase recreational fishing opportunities. Faster growing, more prolific breeders, and more aggressive than the native brook trout, these invasive species compete for food and force brook trout into less desirable habitats or in some cases, eliminate them from streams. PlantsGreat Smoky Mountains National Park staff have identified approximately 380 species of non-native and invasive plants in the park, including kudzu (Pueraria montana), mimosa (Albizia julibrissin), and Oriental bittersweet (Celastrus orbiculatus). Invasive plants often thrive in disturbed areas, and once established, aggressively compete with native vegetation, disrupting natural succession. Additionally, they pose challenges such as interbreeding with closely related native species and outcompeting rare plants that depend on specialized habitats. ManagementAccording to National Park Service policy, management of invasive species, up to and including removal, will be undertaken whenever such species threaten preserved resources in the park. Great Smoky Mountains National Park adheres to this policy, provided that control programs do not cause significant damage to native species, natural ecological communities or processes, or historic objects. Management procedures vary depending on the invasive species. 
NPS Hemlock woolly adelgid conservation effortsBiological and chemical controlsIn its native range, the hemlock woolly adelgid (HWA) has natural predators; however, there are no native predators for HWA in the Smokies. With the assistance of partners, the park has released a HWA predator beetle native to Japan, the derodontid beetle (Laricobius osakensis), as well as the silver fly (Leucotaraxis spp.), which is native to the Pacific Northwest region of the U.S. Additionally, the park uses chemical controls such as slow-release tablets, soil drenching, and stem injections with insecticides (5–7-year intervals) as management strategies. Monitoring and researchMonitoring and research efforts are crucial to understanding the health of eastern hemlock trees and developing effective conservation strategies. Evaluating HWA populations, tree health and predator presence, facilitate a steady reduction in chemical treatments. The park and partner universities continue to engage in proactive stewardship. AccomplishmentsGreat Smoky Mountains National Park's acclaimed ‘Eastern Hemlock Conservation’ program has safeguarded hundreds of thousands of this vital foundation species. The presence of healthy, high-value eastern hemlock trees throughout the park showcases the effectiveness of the program. Through cost-effective chemical treatments, the park has prevented many eastern hemlock trees from becoming hazard trees, thereby enhancing visitor safety and reducing the need for tree removal. Progress toward the long-term goal of achieving a sustainable predator beetle-HWA balance is evident, with the documented establishment of viable predator beetle populations over multiple seasons serving as proof that these predators are now widely distributed across the landscape. The program's efforts include the release of biological controls, chemical treatments, community outreach, monitoring, and research, underscoring the commitment and collaborative efforts of park staff, researchers, and partners such as Friends of the Smokies, Smokies Life, conservation funds, and the US Forest Service Forest Health Fund. 
Steve Moore Native trout conservation effortsThe park stopped stocking rainbow trout and northern hatchery strain brook trout in 1975 and now allows fishing for brook, rainbow, and brown trout. Current management efforts include the removal of both invasive and non-native trout species from streams where they coexist with native species if there is a barrier to reinvasion, the stream segment is of feasible size to restore, and there’s a history of brook trout being present. Park biologists use natural barriers, such as waterfalls and cascades, to separate brook trout populations from rainbow and brown trout populations. Wild hog control effortsCurrently, an effective strategy for controlling wild hogs involves removal through trapping. Park staff also conduct rooting surveys and monitor vegetation to assess hog distribution and identify areas requiring exclosures. Exclosures are areas that are fenced to prevent hog access. This setup allows researchers to study the ecological impacts of excluding invasive species on both plant and animal communities. The goals for management of wild hogs in the Smokies are to protect natural processes, cultural resources, and park infrastructure from the destructive rooting behavior of hogs. Current priority control areas include where rare plant species are present, where vunerable habitats like wetlands, historic homesites, cemeteries, high-elevation beech forests and seeps, and where rare plant species are present. Park staff employ a mix of management tactics that vary based on the resources at risk, environmental conditions and wild hog behavior and population density. The appropriate method or combination of methods, such as trapping or exclusion with fencing, is determined by using the best surveillance information available. Park staff trap and cull approximately 300 wild hogs per year, primarily through trapping in a corral. Vegetation managementLearn more about the park vegetation management team, which focuses on controlling invasive plants and animals, forest insects and diseases, and native landscape restoration projects in the park. Learn More About How You Can HelpThere are many ways that you can protect ecosystems from invasive species.
|
 |
|
Last updated: June 27, 2025