People have made many changes to the world they live in and some of these have had harmful consequences. As the world population increases, there is more need for bigger cities, new towns and farming land. Land has to be cleared, destroying the habitats of many animals and plants. Some of these are now extinct and others are in danger of becoming so. Hunting has also put animals in danger.
There is now nearly three times as much desert in the world as there was 100 years ago. This is partly due to farmers over-grazing their animals on the meagre grass and shrubs and to the clearance of woodland trees for firewood.
Industrialization is a major threat to the environment. Pollution is just one example. Factories discharge harmful chemicals into rivers and seas, killing fish and plants.
The production of chlorofluorocarbons (CFCs) is reckoned to be responsible for damaging the ozone layer, the protective layer in the Earth’s atmosphere that prevents harmful rays from the Sun reaching the surface. CFCs are synthetic chemicals used in aerosol sprays and refrigerators. When they are released into the atmosphere, they destroy the ozone. There is now a hole in the ozone layer above Antarctica.
Air pollution is caused by fumes and smoke from vehicles, factory chimneys and power stations. Poisonous gases, such as sulphur dioxide, mix with rain and mist to produce acids. When the acid rain falls, it kills plants over a wide area. Burning fuels also causes a build-up of carbon dioxide.
Carbon dioxide and CFCs are both greenhouse gases. In the right amounts, greenhouse gases in the atmosphere trap heat from the Sun so the Earth is not too hot or too cold. But if the greenhouse gases build up, too much heat is trapped and the Earth becomes warmer. This change in climate, known as global warming, could have disastrous effects. The ice in the Polar Regions may melt, causing severe flooding to low-lying areas. Changes in the climatic pattern worldwide could lead to violent storms and long droughts.
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