A preservationist generally refers to one who wishes to preserve a historic structure from demolition or degradation.
Persons who work to preserve ancient or endangered languages are also referred to as preservationists.
It is also occasionally used as a derogatory label by those who wish to discredit conservationists and environmentalists. The environmental and conservation movements do wish to preserve ecosystems and the natural environment but this is best described as conservation or environmentalism rather than preservation. Though in casual discussion these terms could get confused, it would be better to recognize their differences and correctly distinguish between a conservationists and preservationists in the field of environmentalism.
A key difference between the Preservationist and Conservationist schools is their view of the use of environmental resources. In summary, Preservationist view is that the environment has an intrinsic value; that is, the environment has value solely in itself. Therefore the name "preservationist" is explaining the goal to preserve the environment is its natural form, making as little change as possible.
Conservationists, however, view the environment with an instrumental value. While conservationists are to be considered far more "environmentally friendly" than many, they do not have the same "let it be" view as preservationists do. Instead, they look at the environment and look for what it can do.
A key concept is that conservationists generally accept the notion of sustainable yield—that man can harvest some forest or animal products from a natural environment on a regular basis without comprising the long-health of the ecosystem. This theory was presented by forester Gifford Pinchot. Preservationists usually oppose any resource extraction.
Preservationism has also been defined by Richard Heinberg in the book Power-down as a term distinguishing between survivalist groups who wish merely to survive a collapse of civilization, and communities who wish to preserve as much of human culture as is possible in the event of collapse. Such communities hope to provide useful knowledge and skills, as well as maintain and continue to form cooperative bonds with other such groups. The idea of preservationist communities is part of a broader strategy in which individuals achieve independence from the centralized power grid, forming sustainable communities that could provide mutual support in the event of critical depletion of non-renewable resources.