Introduction
In New York zoo at the end of an exposition behind the cells of lions and tigers we can see a stone building. The strong thick lattice reserves glass showcase. The inscription above it says: The most dangerous animal in the world! And when the intrigued visitor approaches his face to the lattice, he sees himself: a back wall of a crate is a mirror! Certainly, it is a joke, but bitter joke, and it contains the deep sense and reproach.
Before and now
As we all know, the human beings are children of the Earth. Since ancient times the nature has served the man, being the source of his life. The number of people was small, and they could not make much damage. The air was fresh and clear, the water was tasty, and there were plenty spies of plants and animals. For thousands years people lived in harmony with their environment and it seemed to them that natural riches were unlimited. But with the development of civilization mans 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.
Some facts
Every year world industry pollutes the atmosphere with about 1000 million tons of dust and other 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 rivers and lakes dry up. The pollution of air and the worlds ocean, destruction of the ozone layer is the result of mans careless interaction with nature, a sign of the ecological crises.
Let's analyze some examples of ecological problems.
The most serious problems
A) The ozone hole
The ozone layer or ozonosphere is a region of the stratosphere containing relatively high concentrations of ozone. The ozone layer prevents most ultraviolet (UV) and other high-energy radiation from penetrating to the earths surface but does allow through sufficient ultraviolet rays to support the activation of vitamin D in humans. The full radiation, if unhindered by this filtering effect, would destroy animal tissue. Higher levels of radiation resulting from the depletion of the ozone layer have been linked with increases in skin cancers and cataracts.
Some chemicals destroy the ozone layer. Damage to the ozone layer can also be caused by sulfuric acid droplets produced by volcanic eruptions. A seasonal decrease, or hole, discovered in 1985 in the ozone layer above Antarctica was the first confirmation of a thinning of the layer. In 2000 (and again in 2003) the hole reached a record size, extending over 10.8 million sq mi (28 million sq km), an area greater than that of North America. But it is not so pessimistic. Recovery of the ozone layer, however, is expected to take 50 to 100 years.
b) The radiation pollution
The radiation pollution is a very dangerous negative effect. It can damage humans and animals. Radiation can destroy any type of molecule by causing it to lose electrons. How much damage radiation causes to a living thing depends on its resiliency. If radiation destroys certain enzymes, you might just get sick. If radiation damages DNA and the body cannot repair itself, then cancer is a likely risk.
The most horrible ecological disaster befell Ukraine and its people after the Chernobyl tragedy in April 1986. The territory of Russia, the Ukraine and Byelarus were polluted with radioactive substances. A great damage has been done to the agriculture, forests and peoples health. The consequences of this explosion at the atomic power-station are tragic for the Ukrainian, Byelarussian and other nations.
