Much of the improvement in material living standards in the Third World is attributable to the exploitation of nonrenewable resources such as fossil fuels and metallic ores, and to the exploitation of renewable resource systems at rates that cannot be sustained. This state of affairs presents a serious problem for the future; just as may be the case for the developed regions, a long-term perspective shows clearly that Third World countries must return to a greater dependence on renewable resources while also avoiding irreversible degradation of renewable systems and learning to manage these...