Kategorie: Biológia (celkem: 966 referátů a seminárek)

Informace o referátu:

  • Přidal/a: anonymous
  • Datum přidání: 01. července 2007
  • Zobrazeno: 2050×

Příbuzná témata


The environment means surroundings in which people, animals and plants develop and exist. More simplified it’s the world in which we live. The science that studies the relationship between different life forms in nature is ecology. Today the most serious ecological problems are: the pollution of the air, water and soil, the destruction of ecosystems and its balance, the disappearance of species of animals and plants, the weather changes, acid rains, the warming up of the earth surface, the destruction of tropical rainforests and breaking of the ozone layer. These damages are caused by the man himself and his technical progress.

Global warming and greenhouse effect
Scientists say the temperature of the earth could rise by 3°C over the next 50 years. This may cause draught in some parts of the world and floods in others, as ice at the North and South Poles begins to melt and sea levels rise. This is caused by the greenhouse effect. Normally, heat from the sun warms the earth and then escapes back into space but carbon dioxide and other gases in the atmosphere trap the sun’s heat and this is slowly making the earth warmer. And where does the CO2 come from? Well, people and animals breathe in oxygen and breathe out CO2. Trees take CO2 from the air and produce oxygen. But we produce CO2 also when we burn coal, oil, petrol, gas or wood. In the last few years people have burned huge areas of rainforests. This means that there are fewer trees and consequently more carbon dioxide. So another problem is:
There are two reasons for destroying the world’s forests: land and wood. The land is needed for crops and wood is exported and used for buildings or made into furniture. Unfortunately, many rainforests grow on poor soils and when the trees are cut down, the soil is washed away by the rain or blown away by the wind soon, and the area may turn to desert. But many plants and animal species that live there could become extinct. All of us are to blame for this disaster. However, some people can’t sit passively. They join some organizations which try to save the nature in the world. World Wildlife Fund is one of these organizations, too. It protects endangered spaces, saves endangered species and informs about global threats. In the world there are many animals and plants we have to protect.

All these endangered species are listed in the Red lists.

The ozone layer and ozone hole
The ozone layer is a layer of gas high above the surface of the earth that helps to protect it from the sun’s ultraviolet radiation, which can damage our skin and cause cancer. Scientists have recently discovered holes in the ozone layer, caused by substances called CFCs (chlorofluorocarbons). CFCs are used in refrigerator, aerosol cans and in the manufacture of some plastic products. Some companies now make aerosols that don’t contain CFCs, and these are often marked ozone-friendly.

Factories, power stations and motor vehicles pump large amounts of carbon dioxide and other waste gases into the air. This is the major cause of the green house effect. A lot of petrol contains lead, which is very poisonous and can cause brain damage in children. Many people now prefer using unleaded petrol. Some poisonous gases dissolve in water in the atmosphere and then fall to the earth as acid rain. Acid rain damages trees and buildings, and can kill fish in lakes and rivers. Rivers can also be polluted by industrial waste from factories and chemical fertilizers and pesticides used by farmers.

There are several groups which try to protect the environment. The most famous group is Greenpeace which makes campaigns in many countries around world. They have made campaigns against hunting whales, pollution in the North Sea, nuclear power and testing of nuclear weapons and many others issues. Greenpeace supporters organize demonstrations and they also take direct actions. For example, they block pipes that pour pollution into the sea. Another important environmental group is Friends of the Earth. They have led campaigns against global warming, the destruction of the rain forests.

Alternative energy
Most of energy we use today comes from coal, oil and gas. But these will not last forever and burning them is slowly harming the atmosphere. We need to look for other ways of supplying energy.
Solar power is a way of using the sun’s energy as heat or to make electricity. We can also use wind power by building modern windmills that spin in the wind. There are several types of water power: river water in mountains areas can be used for hydroelectric power, and we can also create electricity from sea water flowing in and out with the tides.

Recycling is the processing of used objects and materials so that they can be used again. About 60% of rubbish from homes and factories contain materials that could be recycled. Recycling saves energy and raw materials and also reduces damage to the country side. Glass, paper and aluminium cans can be recycled very easily.

Many towns have bottle banks and can banks where people can leave their empty bottles and cans for recycling. A lot of paper bags, writing paper and greeting cards are now produced on recycled paper.

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