Since ancient times nature has served man… 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.
Large cities with thousands of smoky industrial enterprises have appeared all over the world today. The byproduct of their activity pollutes the air we breathe, the water we drink, the land we grow grain and vegetables.
Every year world industry pollutes the atmosphere with about 1000 million tons of dust and 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 lakes and rivers 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 crises.