Unit 5 Text 1. Man and his environment

The problem of man and his environment has become one of the most difficult problems for many sciences due to its great significance for the whole of mankind. We see at present signs of ecological imbalance, which may cause a crisis if due measures are not taken.

The air we breathe, the earth we live on and its rivers and seas are becoming polluted with bу-products of man's activities. Маn depends for his life on what the biosphere provides: water, oxygen, food, etc. But the biosphere is strongly affected by all sorts of human activities. For example, man creates new compounds, new substances, pure chemical elements which are unknown to biosphere. They do not belong to the natural cycle of matter and weaken the capacity of natu­ral processes for self-regulation.

The increasing noise level is a special problem nowadays. We need silence as much as we need fresh air and unpolluted water. Noise does not only do physical damage to the hearer but can weaken his energy and break down his nerves. Many cities now are too noisy to live in. In fact, progress can be blamed for many environmental problems.

Transport is a major source of environmental pollution. Every car consumes many tons of air. Its exhaust gases contain poisonous carbon dioxide which makes difficult the emission of the earth's heat into space. New roads spoil the countryside and bring noise and pollution to thousands of homes.

One more aspect of the problem is water pollution. The pollution from industry can occur intentionally, when factories discharge their effluents directly into rivers, lakes and oceans, or unintentionally, when accidents cause leakage of toxic waste into the water supply. Sea- and river-going ships often pollute sea and river water with various oil products. At a rough estimate, no less than five million tons of oil are discharged into seas and oceans each year, and one ton of oil can spread over about twelve square kilometres of the water surface as a fine film which prevents air-water oxygen exchange. One litre of oil makes one million litres of fresh water unfit for drinking.

We must stop the contamination of our water­ways which comes from so many sources: chemical waste from factories, thermal waste from power stations, domes­tic waste from cities and towns and so on. The volume of both industrial and domestic waste has increased dramatically over the past 50 years. Industrial air pollution includes the greenhouse gases carbon dioxide and chlorofluorocarbons. It also includes sulphur dioxide and nitrogen oxides, which lead to acid rain.

The balance of nature within any ecosystem depends on the complex interaction between millions of species of animals, plants and microorganisms. The death of one species could threaten the survival of hundreds of others. The balance of nature is often a very precarious one. There are many more species of small organisms than of large ones. Changes in the populations of microorganisms may cause major changes in the composition of the earth and its atmosphere.

Extinction is final. Once the last member of a species has died, that species is lost to the planet forever. This is why we must try to protect every living species on the earth — even the ugliest insects and the tiny, invisible bacteria. Of all the world's resources, its genetic resources are the least renewable of all.