Many thousands of years ago, much of the world's land area was covered in forests. Since that time, people have needed to clear the forests by cutting down the trees in order to make room for their farms and cities. Today, forests are still being cleared, and many people are worried that too much forest area is being lost. There are many reasons why it is important to preserve forests. One reason is that the trees inside the forests help to remove carbon dioxide from the air and put oxygen back into the air. This is important, because scientists believe that too much carbon dioxide in the air might be causing the world's temperature to increase quickly. The forests might help to reduce this problem by absorbing carbon dioxide from the air. Another reason for preserving forests is to maintain many different species of plants and animals. The forests are the home of a huge variety of plants and animals, which will become extinct if the forests are destroyed. These plants and animals are both beautiful and interesting, but they also have practical benefits for people. For example, doctors believe that many diseases might be treated by chemicals that are obtained from forest plants. Forests are also important for providing wood, or lumber, but sometimes people cut down too many trees for lumber. To preserve the forests, it is important to ensure that the amount of wood removed is not more than the amount of new wood that grows in the forest. Otherwise, the forest will gradually disappear. In many parts of the world, forests have already been cleared. In recent years, many forests have been cleared in South America, Africa, and southeast Asia. In other parts of the world, the forests had already been cleared a long time ago. There are only a few areas of the world where very large areas of forests have not yet been changed by people. These areas include the Amazon rain forest of Brazil, and the northern forests of Canada, Alaska, and Siberia. Some countries have passed laws to protect their forests from being cleared. For example, a country can declare its forest areas to be a national park and prevent the forests from being cut down. However, this is very difficult for poor countries to do. The people may want to cut down the forests to obtain wood, to gain access to natural resources in the forest areas, or to have new land for farming. When forests are cut down to gain new farmland, however, people usually find that the soil is not very good for farming. It is a difficult challenge to provide opportunities for poor people of these countries, and to protect the forests at the same time. However, it is very important that this challenge be met successfully because the forests will be needed by future generations of people.
