Since ancient times Nature has served man, being the source of his life. For thousands of years people lived in harmony with environment and it seemed to them that natural riches were unlimited. But with the development of civilization man’s interference in nature began to increase.

Every year world industry pollutes the atmosphere with about 1000 million tons of dust and other harmful substances. Many cities suffer from smog. Vast forests are cut and burn in fire. Their disappearance upsets the oxygen balance. As a result some rare species of animals, birds, fish and plants disappear forever, a number of rivers and lakes dry up.

The pollution of air and the world’s ocean, destruction of the ozone layer is the result of man’s careless interaction with nature, a sign of ecological cities. Environmental protection is of a universal concern. That is why serious measures to create a system of ecological security should be taken.