Text 2 Trees in danger

Millions of years before animals lived on land, there were trees on the Earth. But today trees are in serious danger.

In the 1970^th, many of the elm trees were killed by Dutch elm disease. Now an even greater danger is threatening the forests and woods of Europe from northern Sweden to southern Italy. This new danger attacks all trees – deciduous trees like oak, beech and birch as well as coniferous trees like fir and pine.

First the branches turn yellow end brown. Then the trees needles or leaves fall. The roots and the trunk shrink. Finally the trees die. In file Black Forest in southern Germany 75% of the trees have been damaged or killed (figure 2.5).

But what is killing the trees? It is air pollution or acid rain.

2.8 Study figure 2.4 and tell about Bark beetle life cycle.

Acid rain is not new. We started producing acid rain when we started building a lot of factories and power stations which burned coal or oil. When you burn these fuels, you produce the gases SO₂, and NO_x (sulphur dioxide and nitrogen oxide). These substances mix with water vapour in the atmosphere and form sulphuric acid and nitric acid. Sunlight turns these acids into poisonous oxidants which fall in rain or snow onto the trees.

B

Figure 2.5 Trees killed by acid rain

ritain produces about five million tonnes of these gases every year. China produces eighteen million tonnes. The USA produces more than twenty million tonnes. The wind carries the gases high into the sky. There they come together with water in the air and make acid rain, acid fog and acid snow. In Canada and northern Europe many millions of trees have died because of acid rain from power stations and factories thousands of kilometres away.

What can be done about acid rain? Why don’t governments do something to save the trees? Unfortunately, acid rain doesn’t always fall on the countries which produce the pollution. The wind carries the poisonous substances from one country to another. Why should the people of one country pay to save another country’s trees?

In other parts of the world trees are threatened by people, not by pollution. The great rain forests of Asia and South America are being destroyed for firewood and building material. Something must be done. Trees are important because they provide a home for many other plants, and animals too. They protect the flowers which grow on the forest floor. They provide food for insects, reptiles, birds and mammals. They protect the soil from the wind and the rain. Most important of all, the forests are the lungs of the planet. Trees produce the oxygen which we breathe. If the trees die, we will, too.

2.9 Read the text 3 without a dictionary. Text 3

Russian forests are prone to numerous disturbances such as wild fires, insect invasions, and diseases. About 60% of the forested area of the country is protected against fires. The State Forest Guard and Specialized Regional Units of “Rosavialesookhrana” (forest fire control by means of aircraft) involve the local population in controlling forest fires. About 15,000-30,000 forest fires covering nearly 500,000-3,000,000 ha are registered annually. In the years with a medium level of fire risk, the Forest Guard provides a sufficient level of fire control. In the extremely dry years, which recur every 10-15 years, fires run out of control and become a kind of catastrophic calamity. During the last such dry year (1998), vegetation fires covered 9.5 million ha of Asian Russia. According to remote-sensing data, timber losses exceeded 500 million m^3. Insect invasions and diseases occur every 10-15 years and can occupy millions of hectares. Areas of pest and disease eruption accounted for, on average, about 3 to 4 million ha per year over the last decades. Losses of forest caused by these phenomena are comparable with those of fires. Forest protection measures(air- and land-based) are taken in an area of 350,000-900,000 ha each year.