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1.... The tropical rainforests surround the earth equator like a belt. They occupy the total area of about nine million square kilometers. The largest rainforests are in South America. The rainforests are rapidly being cut down. Nobody knows exactly how much is cut down every yr...
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| 2. The world's water crisis is simple to understand, if not to solve. The amount of water in the world is finite. The number of us is growing fast and our water use is growing even faster.
A third of the world's population lives in water-stressed countries now. By 2025, this is expected to rise to two-thirds. There is more than enough water available, in total, for everyone's basic needs.
The UN recommends that people need a minimum of 50 litres of water a day for drinking, washing, cooking and sanitation.
In 1990, over a billion people did not have even that. Providing universal access to that basic minimum worldwide by 2015 would take less than 1% of the amount of water we use today. But we're a long way from achieving that.
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| 3. Early in December 1952, a cold fog descended upon London. Because of the cold, Londoners began to burn more coal than usual. The resulting air pollution was trapped by the inversion layer formed by the dense mass of cold air. Concentrations of pollutants, coal smoke in particular, built up dramatically. The problem was made worse by use of low-quality high-sulfur coal for home heating in London in order to permit export of higher-quality coal, because of the country's tenuous economic situation. The "fog," or smog, was so thick that driving became difficult or impossible. It entered indoors easily, and concerts and screenings of films were cancelled as the audience could not see the stage or screen.
Since London was known for its fog, there was no great panic at the time. In the weeks that followed, the medical services compiled statistics and found that the fog had killed 4,000 people—most of whom were very young or elderly, or had pre-existing respiratory problems.
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| 4. The extinction of many species of birds has undoubtedly been hastened by modern man; since 1600 it has been estimated that approximately 100 birds species have become extinct over the world. In North America, the first species known to be annihilated was the great auk, a flightless bird that served as an easy source of food and bait for Atlantic fisherman through the beginning of the nineteenth century. As the birds became scarce, they were collected for a well-paid trade in skins and eggs. The last known living pair and one egg were taken in Iceland in 1844, and the great auk is now represented in collections only by bones, skins, and eggs.
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| 5. Overall cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction.
Since the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increases in skin cancer.
An increase of UV radiation would also affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are very sensitive to UV light and they would be affected by its increase.
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| 6. When we think of wildlife facing extinction, we are usually thinking of large majestic animals such as whales, elephants and rhinos or of the "cuddly" black-and-white panda. These creatures are indeed in risk of extinction because of irresponsible and cruel hunting by human predator.
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2015-08-21
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