A public bad, in green economics, is the opposite of a public good. Pollution is the most obvious example. There are less obvious examples. A public golf course, for instance, could be seen as a public good insofar as it provides recreation to those who might not otherwise get it. But deforestation and pesticide use to maintain it might well be seen as public bads, externalizing harms on future and current generations.

Most green economists advise measuring such impacts back to the present from the seventh generation. Thus in the golf course example, both the recreation and the negative impacts from deforestation, associated habitat and biodiversity loss, and pesticide toxicity would be estimated across those generations and some amortization applied to determine whether the golf course was a public good or a public bad from the point of view of that seventh generation.

See also : waste