Photos from an air quality monitoring station show affect of pollution on visibility in the park. The left side photo was taken on a day with good visibility. The right side photo was taken on a day when visibility was reduced due to air pollution.
Among the oldest mountains in the world and the highest in the Appalachian chain, the Smokies have been both a daunting obstacle and a source of inspiration since the earliest people set foot on the mountains' slopes. But long before humans arrived, geologic processes, climatic shifts, weather, and fire shaped this environment, producing an ever-changing ecosystem.
More recently, human-caused factors such as air and water pollution and non-native species have had a significant impact on natural resources-both here and worldwide. The further impacts on the park of ten million human visits each year are only just beginning to be measured and mitigated. Scientists are striving to better understand these impacts on the park's ecosystem. Park staff carefully monitor threats such as air pollution and destructive non-native species and endeavor to implement proactive measures to preserve the park's valuable resources.