During the 19th century, much of the mountain was denuded by logging, fires, and grazing. Forests have since reclaimed the mountain. Several forest communities exist on Mount Greylock. Lower slopes are inhabited by northern hardwood forest species while upper summits are dominated by boreal balsam fir and red spruce. The ridgeline of Greylock, between Mount Fitch on the north and Saddle Ball on the south, is the only place in Massachusetts where a taiga-boreal or sub-alpine forest flourishes. Researchers have identified of old growth forest on the mountain. The steep western slopes (which include The Hopper) contain northern hardwood forest biome species up to 350 years old, including a red spruce. Because of its extensive stands of red spruce old growth, The Hopper has been designated a National Natural Landmark.