The establishment of Great Smoky Mountains National Park in 1934 protected its forests from logging, which was widespread in the eastern United States. Between 100,000 and 200,000 acres of the park's forest are old-growth, surviving to park designation by virtue of their especially rugged surroundings.
The Smokies' proximity to some of the East's major industrial and population centers means the park faces issues of outside-source pollution. Haze carried by prevailing winds sometimes clogs mountain views; this whitish obscurity deriving from particulate matter is distinct from the Smokies' characteristic bluish mist. Acid rain is a greater threat here than in any other national park.
Like many places around the world, the Smokies are dealing with a flood of "non-native," invasive species associated with humans. Feral pigs, for example, descended from European stock root up mountainsides and even prey on small animals, including some of the Southern Appalachians' famous, highly unique salamanders. Other invasives include plants like the kudzu and hemlock- and fir-targeting insects called adelgids.
While the Park Service today recognizes fire's role in Smoky Mountain ecology, fire suppression policies of previous eras have had big repercussions in the mountains, which historically experienced occasional lightning-sparked wildfires. Without wildfire, forests began to shift in composition, with clear ecological effects. Table Mountain pine, for example, which depends on fire to open its see-bearing cones, has declined in the park, and the red-cockaded woodpecker, which nests in pines clear of surrounding underbrush, is threatened by thickening timber.
Light and Sound
A subtle but profound environmental problem is that of light and sound pollution from surrounding population centers. The national park is presently engaged in a night-sky and sound-scape monitoring program to better define the extent and nature of these threats, which intrude upon the Smokies' wilderness clarity.