“…As examples we may note that water shortages in developing countries cause diseases that, through workdays lost to sickness, levy a cost of $125 thousand millions a year (Pearce, 1993); with this we should contrast the cost of supplying both water and sanitation facilities, namely $50 thousand millions per annum (Christmas & Rooy, 1991). Again, desertification leads to agricultural output worth $42 thousand millions per annum being lost, whereas an anti-desertification programme would cost between $10 thousand millions and $22 thousand millions per annum (United Nations Environment Programme, 1991;Chou & Dregne, 1993).…”