The mountain's summit is coated in a dense stand of Southern Appalachian spruce-fir forest, which consists primarily of two evergreen species— the red spruce and the Fraser fir. Most of the mature Fraser firs, however, were killed off by the non-native Balsam woolly adelgid in the latter half of the 20th century. The high elevations expose plant life to high levels of pollution, including acid precipitation in the form of rain, snow, and fog. These acids damage the red spruce trees in part by releasing natural metals from the soil, such as aluminum, and by leaching important minerals. To what extent this pollution harms the high-altitude ecosystem is debatable.