5. The problems of ecology. What should we do to protect our planet?
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. Large cities with thousands of smoky industrial enterprises appear all over the world today. The by-products of their activity pollute the air we breathe, the water we drink, the land we grow grain and vegetables on. Every year world industry pollutes the atmosphere with about 1000 million tons of dust and other harmful substances. Many cities suffer from smog. Cars and factories pollute the air we use. Their fume also destroys the ozone layer which protects the Earth from the dangerous light of the Sun. People who live in big cities are also badly affected by the increasing noise level which is as bad for human health as lack of fresh air and clean water. Vast forests are cut and burn in fire. Their disappearance upsets the oxygen balance, changes the climate and ecosystem in the world. As a result some rare species of animals, birds, fish and plants disappear forever. Water pollution is caused by dumping wastes into lakes, rivers, and other bodies of water. Harmful wastes may also soak into the soil, or drain or run off from fields that have been sprayed with pesticides. Pesticides are often used to kill insects and weeds in cities or on farms. Polluted water can spread many diseases. In my opinion the most urgent problem is global warming. World temperatures are currently rising every year. It is caused by the build-up of gases and water vapour in the atmosphere. These gases form a layer that reflects the heat back to Earth, rather than allowing it to escape into the outer atmosphere. As the planet warms up, the water in the oceans will take up more space and water locked up in glaciers and the polar ice caps...
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