ABSTRACT
For most of history, 1i'1e capacity of human beings to affect the environment was limited and local, though the massive projects of ancient civilizations and the denuding of lands around the Mediterranean show what was possible even in pre-industrial times. Today, human activities have grown to the point where they affect many of the large-scale physical systems of the planet. Present day actions also have consequences that reach far into the future. The impact of present policies, for example on energy and infrastructure, will extend well beyond the lifetimes of those who initiated and implemented these projects. Despite their inherent uncertainties, projections and forecasts are becoming increasingly popular as a basis for decision making. Conversely, the 'future' is playing an increasing role in the present. The future impacts of today's decisions are becoming more and more prominent in current -day policy making.
