As evidenced by the participation of most of the world's leaders in the United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, Brazil, June 1992, the phenomenon of global change is perceived as one of the most critical challenges facing the world today. Physical and socio-economic evidence of global change related phenomena such as ozone depletion, loss of biological diversity and changes in rainfall patterns and intensity, can be found in all areas of the world. Regardless of whether the particular phenomenon is natural or human-induced, its effects often cross geopolitical borders. Thus, many environmental issues must be addressed scientifically as global or regional problems, with steps towards mitigation or alleviation taken at a national level.