The National Park Service (NPS) accommodates nearly 300 million visitors per year, visitation that presents managers with substantial challenges at some 394 park units across some 83.6 million acres of protected lands. An increasing number of visitors inevitably contribute negative effects to fragile natural and cultural resources. Such visitation - related resource impacts can degrade natural conditions and processes and the quality of recreation experiences. According to the NPS Management Policies: ―The fundamental purpose of the national park system , established by the Organic Act and reaffirmed by the General Authorities Act, as amended, begins with a mandate to conserve park resources and values...The fundamental purpose of all parks also includes providing for the enjoyment of park resources and values by the people of the United States.‖ (NPS 2006 b , Section 1.4.3). However, what might appear to be dual mandates, visitation and resource protection, are clarified to reveal the primacy of resource protection. The Management Policies acknowledge that so me resource degradation is an inevitable consequence of visitation, but directs managers to ―ensure that any adverse impacts are the minimum necessary, unavoidable, cannot be further mitigated, and do not constitute impairment or derogation of park resources and values‖ (NPS 2006 b ).