In 1916, the U.S. Congress declared the fundamental purpose of parks and mandated the National Park Service to conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for future generations. Accordingly, the National Park Service manages the animals and plants and their environment to minimize human interference. People and their environment have always interacted. Pre-Columbian humans in North America used fire, for example, to alter vegetation and to capture some animals. Today, habitats around parks are often developed and the landscapes around the parks are fragmented.
Pollution affects air, water, animals, and plants.
Human intervention may be needed to reverse adverse effects of human actions. Such intervention includes protection of native plants and animals and restoration of species that humans eliminated from parks. Determining the kind and extent of necessary management is difficult. It requires information about the status of the plants and animals, understanding of the environment around the park and of human social structure and needs, and careful examination of the purposes for which the Congress established a specific park. The information must be gathered with species inventories, population monitoring, and research on the interactions of the animals and plants with their environments.