The basic principle of environmentalism is that nature (i.e., “the environment”) has intrinsic value—value in and of itself, value apart from and irrespective of the requirements of human life—and that this value must be protected from its only adversary: man. Rivers must be left free to flow unimpeded by human dams, which divert natural flows, alter natural landscapes, and disrupt wildlife habitats. Glaciers must be left free to grow or shrink according to natural causes, but any human activity that might affect their size must be prohibited.
In short, according to environmentalism, if nature affects nature, the effect is good; if man affects nature, the effect is evil.