for a very fortunate minority of the world's population living in the advanced economies,the consequences of all this activity have been a vast increase in the standard of living and the removal of most of life's risks and uncertainties. However,this has not been without its price,and some of the most serious problems that man faces arise from the increasing demands, that he is placing on the environmenta These demande,which are now piacing a severe strain on some areas and some resources,are caused by the interaction of four main factors