Mr Lester R Brown has pointed out in his book ‘The Global Economic Prospect’ that there are four principal biological systems of the earth. These are : fisheries, forests, grasslands, and croplands. They form the foundation of the global economic system. In addition to supplying our food, these four systems provide virtually all the raw material for industry except minerals and petroleum-derived synthetics. But unfortunately, in large areas of the world, human claims on these systems are reaching an unsustainable level, a point where their productivity is being impaired. When this happens, fisheries collapse, forests disappear, grasslands are converted into barren wastelands and croplands deteriorate. In a protein-conscious and protein-hungry world, over-fishing is common every day. In poor countries, local forests are being decimated in order to procure firewood for cooking. That is why these four systems are being depleted.
