Constant scorching of the forest for human activities, such as raising cattle, is steadily reducing the amount of forested land on earth. The problem is that rain forest soil is poor for grasses and crops. Once the land has been used up, and that takes only a few years, it will not support new growth. It erodes away in the rain leaving wastelands.

Today, severe deforestation occurs in tropical areas, primarily as a result of the clearing of land for agriculture and industry. Until the late 1940's, tropical rain forests covered about 6 million square miles (16 million square kilometers) of the earth's land. In the late 1980's, they covered only about 4 million square miles (10 million square kilometers). Scientists estimate that as many as 50 million acres (20 million hectares) of tropical rain forests are destroyed each year. Most of this destruction occurs in Latin America and Southeast Asia.

In other parts of the world, industrial pollution is a chief cause of deforestation. Factories often release poisonous gases into the air and dangerous wastes into lakes and rivers. Air pollutants may combine with rain, snow, or other precipitation and fall to earth as acid rain. These pollutants can restrict plant growth in a region and eventually kill most plants there. In parts of Europe, forest areas set aside long ago for continuous timber production have been seriously damaged by industrial pollution. Pollution also threatens forests in eastern North America. ²

Deforestation has many far-reaching effects. For example, as forest areas decrease, the amount of oxygen released into the air through photosynthesis also decreases. Renewal of the oxygen supply is vital to the continuing survival of oxygen-breathing organisms. Also, as less carbon dioxide is taken up by photosynthesis, the amounts of carbon dioxide released into the air increases. As a result, more heat from the sun is trapped near the earth's surface instead of being reflected back into space. Many scientists believe that this greenhouse effect is causing a steady warming that could lead to threatening climatic conditions. The destruction of forests also destroys the habitats of many living creatures. Countless species of animals and plants have been wiped out by deforestation.

In the greenhouse effect, carbon dioxide traps sunlight and heat inside the earth's atmosphere. This process is thought by some scientists to be increasing the temperature of the earth.

The third reason for deforestation is environmental pollution. Air pollution and water pollutin from factories can greatly harm and weaken forests, and make them more susceptible to natural forces such as drought and cold. Air pollutantion can be carried by the rain or snow, and fall back onto forests as acid rain, which weakens trees and plants, and can eventually kill whole forests. Two areas where acid rain has been especially hard on forests are in Northern Europe and the the northeast United States. ² This is a difficult problem to solve because the air pollutants are often created hundreds or even a thousand miles away, and are carried to the forest by the wind and weather patterns. The pollution may originate in a different state or even a different country, and those responsible may be reluctant to change their practices.

There are many effects of deforestation besides simply a loss of many trees and plants. Plants convert carbon dioxide to oxygen in the process of photosynthesis. Forests, especially rainforests, produce much of the oxygen that people and animals breath. The less forests, the less oxygen. With fewer forests, less carbon dioxide is turned into oxygen, and more carbon dioxide remains. Carbon dioxide in the atmosphere holds in sunlight and heat, and the more carbon dioxide in the atmosphere, the warmer the temperature of the earth's surface. This is called the "greenhouse effect." Small changes in the temperature can have big effects, including raising levels of the oceans and changing weather patterns. Finally, deforestation destroys the habitats of many animals and plants. Without habitats they cannot survive, and many animals and plants have already gone extinct because of the destruction of their forest homes.