I. Introduction
Sustainable development has become an important part of international and national approaches to integrating economic, environmental, social and ethical considerations so that a good quality of life can be enjoyed by current and future generations for as long as possible. The broad concept of sustainable development gained prominence after the publication of the so-called Brundtland Report ‘Our Common Future’ (WCED, 1987). At the Earth Summit meeting held in Rio de Janeiro in 1992 many national governments pledged them to making development sustainable by the early years of the new millennium.