Презентація на тему «Deforestation» (варіант 2)

Deforestation
Deforestation is the removal of a forest where the land is thereafter converted to a non-forest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use.
 In many countries, deforestation, both naturally occurring and human induced, is an ongoing issue. As we know, forest are lungs of our planet. Forests are the natural air purifiers of the Earth. Forests absorb carbon dioxide from our atmosphere and supply us oxygen. They form the most productive ecosystem of the Earth, providing immeasurable benefits to all living beings on this planet. 
About half of the world's original forests had been destroyed by 2011, the majority during the previous 50 years. Since 1990 half of the world's rain forests have been destroyed.
Deforestation occurs for many reasons: trees are cut down to be used or sold as fuel or timber. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. 
Deforestation affects the earth's physical environment by causing soil erosion, poor water quality, reduced food security and impaired flood protection, according to a report from the World Resources Institute. Because forests are the source of employment and food for many people, their destruction can cause massive migration to cities. With the influence that tropical forests have on weather, particularly rain, deforestation can cause altered weather patterns. 
Deforestation, current and past, is a serious problem around the world, particularly in tropical areas. Countries with significant deforestation include Thailand, Brazil, the Congo and Indonesia, as well as parts of Eastern Europe. 
1) Deforestation of forests has caused poor rainfall since the forests play a vital role in cloud formation and rainfall. 2) Cutting down of trees has seriously harmed the ecosystem. Unique species of trees that have been living for 3000 years have become extinct. 3) Deforestation has caused soil exposure to the sun, wind and rain which has caused loss of vital nutrients of the soil leading to infertility. The harm to the ecosystem causes flood and draught.4) Deforestation has a direct effect on the increasing level of carbon dioxide which is the major greenhouse gas responsible for the climatic changes.5) Deforestation causes loss of moisture in the atmosphere. This leads to drier and warmer climate. 6) Forests have been the medicine chest of nature and loss of forest area has reduced the availability of innumerable therapeutic properties. 
Harm of deforestation
The water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer transpire this water, resulting in a much drier climate. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture. Tropical rainforests produce about 30% of our planet's fresh water.
Harm for water cycle
Harm for atmosphereDeforestation is a contributor to global warming, and is often cited as one of the major causes of the enhanced greenhouse effect. Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions. Greenhouse gases are trapped in the atmosphere and act as a barrier for heat that would normally be released into space; as a result, temperatures across the globe rise and change rainfall patterns, ice cover and sea levels.
Reforestation
Now very popular become reforestation. Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation. In many countries people planted new trees and whole plantations to restore the green cover of our planet.