How “natural” must the land be to qualify as wilderness?
An area is considered to be natural if the imprints of human intrusion are “substantially unnoticeable.” The Wilderness Act specifically permits trails, bridges, fire towers, pit toilets, fire rings, fish habitat enhancement facilities, fencing, and research monitoring devices. Other human impacts are permitted in Wilderness areas, so long as their overall impact is substantially unnoticeable. Sights and sounds of activities occurring outside an area are not considered when assessing naturalness, even if these activities are quite prominent.
