Environmentalism

Environmental quality is what economists call a "normal" good. That is, people want more of it as their real incomes increase.The cost of preserving the environment is inherently economic as well. Equipment and labor to clean air or water, for example, have an "opportunity" cost: they could be used to produce something else. How clean the air should be is what economists call a normative issue: people's answers depend on their values.

Though figuring out the efficient amount of environmental quality is difficult, it theoretically is the point at which the value that people put on the last increment of cleanliness equals its cost. After that point additional cleanliness costs more than its value to society.