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.

Ever since people first started clearing land to plant crops, about 11,000 years ago, the amount of forests have been decreasing. Large areas of forest have been cut down to make way for farms, cities, and industry in almost every area of the world. Today, the most severe deforestation is taking place in the tropical rainforests. These rain forests covered about 6 million square miles (16 million square kilometers) until the late 1940's. A third of them were cleared for farming and cities by the late 1980's, and there were only about 4 million square miles (10 million square kilometers) remaining, and the damage continues! Up to 50 million acres (20 million hectares) of tropical rain forests are destroyed each year, mostly in Latin America and Southeast Asia, where human populations are growing, and there isn't enough land available for farming.

Many forests have also been cut down in huge logging operations. The trees are cut up into lumber for building houses, buildings and furniture. This has happened mostly during and since the industrial revolution in the late 1800's when power tools and factories made it possible to perform logging on a much larger scale. Huge numbers of trees and even whole forests have been cut down in many parts of the United States, including New England, the Southeast, the Upper Midwest, and California and the Pacific Northwest.

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.