A natural landscape is a landscape that is unaffected by human activity. A natural landscape is intact when all living and nonliving elements are free to move and change. The nonliving elements distinguish a natural landscape from a wilderness. A wilderness includes areas within which natural processes operate without human interference, but a wilderness must contain life. As implied, a natural landscape may contain either the living or nonliving or both. In his extensive travels in South America, Alexander von Humbolt became the first to conceptualize a natural landscape. Some have described a transition of a pristine landscape state to a humanized landscape state—which includes the human-modified landscape, the primeval landscape, the ancient landscape, the undisturbed wilderness and the managed landscape. The natural landscape is a place under the current control of natural forces and free of the control of people for an extended period of time.