In the self-sustaining system of the biosphere and the ecosystem – the land, water, air and all the living organisms within – nature maintains her own balance. Upset the balance at one point, the stress shows at other, often quite unexpected, places and a chain reaction follows. It has happened in the past but the consequences were localised. Many fertile lands which had sustained ancient civilisations are today buried under mounds of silt, for instance in the Tigris and Euphrates valley, or in South America, because land was ill – managed or used recklessly.
Today’s technological world works as one single unit; the stresses on nature are greater today, and will continue to grow, because of the growing populations. Together, these could have a multiplied effect that could change the face of the earth irreversibly.
What are nature’s balances, anyway, and how does pollution affect them ? First, there are the atmospheric cycles of carbon and nitrogen. The atmosphere consists of nitrogen gas (78 %), oxygen (21 %), carbon dioxide (0. – 3 %) and other gases and water vapour. Green plants absorb carbon dioxide and water vapour, using the sun’s energy, convert them into organic matter and release oxygen into the atmosphere in the process (photosynthesis). Some of the organic matter in decaying bodies, which lie buried under stratified earth, turns into fossil fuels – coal and petroleum – and releases carbon dioxide by burning in association with oxygen.
By - Brendan J. Carroll 
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