This situation has long bothered environmentalists, who want the Park Service to put greater emphasis on conservation. But bad as they are, an emphasis on tourism and a lack of professionalism are not the only threats to the national parks. More damaging is the Park Service's confused jumble of natural-resource policies. The Park Service quite literally does not know what preservation is. Unfortunately, even today no one knows what these statements mean.
Ecosystems are communities of living things undergoing evolution.
We cannot halt change. In an attempt to frame a more scientifically respectable preservation policy, Interior Secretary Stewart Udall in 1963 charged a prestigious commission, chaired by the prominent biologist A. Starker Leopold, with the task of reexamining the purposes of park management. The Leopold Report was embraced by the Park Service that same year. But however attractive, it set the agency a chimerical goal. Taken literally, it would be impossible to accomplish.