David Friedman, a professor of Law and Economics at Santa Clara Law, blogs about sustainability:
The university I teach at is very big on "sustainability." As best I can tell, what it means is doing things in such a way that you could continue doing them forever, or at least for a very long time. Use of fossil fuels is "not sustainable" since, eventually, we would run out. Use of windmills, on the other hand, is. Similarly for a variety of other issues. It sounds very nice if you don't think about it. If you do, it may occur to you that belief in the vital importance of sustainability is based on an implicit assumption of stasis—a world where, whatever you are doing, you will keep doing it forever. That isn't the world we live in. The critical resource of today may be irrelevant fifty years from now; the pollution of today may be a resource then—consider manure—or the resource pollution. Rabbits were a resource—until they became, in Australia, a plague. Similarly for Kudzu in the U.S. We don't know how we will doing things fifty or a hundred years hence, but that it will be the same way we are doing them at present is not a likely guess.