Wilderness or wildland is a natural environment on Earth that has not been significantly modified by human activity. It may also be defined as: "The most intact, undisturbed wild natural areas left on our planet—those last truly wild places that humans do not control and have not developed with roads, pipelines or other industrial infrastructure." The term is usually limited to terrestrial environments, though the seas and outer space also are little developed by people Some governments establish them by law or administrative acts, usually in land tracts that have not been modified by human action in great measure. The main feature of them is that human motorized activity is significantly restricted. These actions seek not only to preserve what already exists, but also to promote and advance a natural expression and development. Wilderness areas can be found in preserves, conservation preserves, National Forests, National Parks and even in urban areas along rivers, gulches or otherwise undeveloped areas. These areas are considered important for the survival of certain species, biodiversity, ecological studies, conservation, solitude, and recreation. Wilderness is deeply valued for cultural, spiritual, moral, and aesthetic reasons.