The lower region forests are dominated by deciduous leafy trees. At higher altitudes, deciduous forests give way to coniferous trees like Fraser Firs.
Altitudes in the park range from 250 to 2,000 meters (875 to 6,643 feet). The wide range of altitudes mimics the latitudinal changes found throughout the entire eastern U.S. Plants and animals common in the Northeast have found familiar ecological niches in the park’s higher altitudes, while southern species find homes in the balmier lower reaches. During the most recent ice age, the northeast-to-southwest orientation of the Appalachian mountains allowed species to migrate southward along the slopes rather than finding the mountains to be a barrier. As climate warms, many species are now migrating northward along the slopes.
The park has a very high humidity and rainfall, averaging from 140 centimeters (55 inches) per year in the valleys to 215 centimeters (85 inches) per year on the peaks. This is more annual rainfall than anywhere in the lower 48 states outside the Pacific Northwest. The park is almost 95 percent forested, of which roughly a quarter is old growth forest with many trees that predate European settlement of the area. It is one of the largest blocks of deciduous, temperate old growth forest in North America.
The variety of altitudes, the abundant rainfall, and the presence of old growth forests give the park an unusual richness of biota. About 10,000 species of plants and animals are known to live in the park, and estimates as high as an additional 90,000 undocumented species may also be present. The park was designated an International Biosphere Reserve in 1976, and was certified as a UNESCO World Heritage Site in 1983.
Original entry was from the NASA Earth Observatory; [1]