Wilderness Act provides a justification for and definition of what constitutes an area of land as wilderness. Wilderness Act land is chosen from existing federal land and by determining which areas are considered to meet the following criteria: Minimal human imprint Opportunities for unconfined recreation At least five thousand acres Educational, scientific, scenic or historical value Have no commercial enterprises within them or any motorized travel or other form of mechanical transport (e.g., vehicles, motorcycles, bicycles). Creation of the National Wilderness Preservation System Section 3 of the Act outlines the creation and regulation of the National Wilderness Preservation System (NWPS). When Congress designates each wilderness area, it includes a very specific boundary line in statutory law. Once a wilderness area has been added to the system, its protection and boundary can be altered only by Congress. The basics of the NWPS set out in the Wilderness Act are straightforward: The lands protected as wilderness are areas of our public lands. Wilderness designation is a protective overlay Congress applies to selected portions of national forests, parks, wildlife refuges, and other public lands. Within wilderness areas, the Wilderness Act strives to restrain human influences so that ecosystems [the Wilderness Act, however, makes no specific mention of ecosystems] can change over time in their own way, free, as much as possible, from human manipulation. In these areas, as the Wilderness Act puts it, "the earth and its community of life are untrammeled by man," untrammeled meaning that the forces of nature operate unrestrained and unaltered. Wilderness areas serve multiple uses but the law limits uses to those consistent with the Wilderness Act mandate that each wilderness area be administered to preserve the "wilderness character of the area." For example, these areas protect watersheds and clean-water supplies vital to downstream municipalities and agriculture, as well as habitats supporting diverse wildlife, including endangered species, but logging and oil and gas drilling are prohibited. Along with many other uses for the American people, wilderness areas are popular for diverse kinds of outdoor recreation but without motorized or mechanical vehicles or equipment except where specifically permitted. Scientific research is also allowed in wilderness areas as long as it is non-invasive. The Wilderness Act allows certain uses (resource extraction, grazing, etc.) that existed before the land became wilderness to be grandfathered in and so they may continue to take place although the area that was designated as wilderness