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The Effects of Humans
From Grolier's The New Book of Knowledge
Highway 1 through the Costa Rican rain forest is subject to mudslides. Above, a truck makes it way along a new road, after the earlier road (right) was washed out by Hurricane Cesar.

Photo Courtesy of Dr. Hays Cummins (

For centuries, humans have relied on rain forests for a variety of products. Foods such as tomatoes, peppers, corn, rice, coconuts, bananas, coffee, cocoa, tapioca, beans, and sweet potatoes all originally came from the rain forest. Many civilizations have exploited the timber in rain forests and cleared the land for farms. Some preliterate tribes have actually lived in the rain forests for thousands of years. Today people rely on tropical rain forests for a variety of everyday products: paper (7 percent of all paper pulp comes from the rain forest); rubber (used in tires and other products); wax (used in plastics); mahogany and teak (used in wood products such as furniture); and many other items.

Destructive Activities

Unfortunately, human activities have taken a toll on the rain forest. Some of the most-destructive practices are discussed below.

Farming. In some areas of the world, the practice of shifting cultivation has destroyed parts of the forest. In this type of farming, a farmer clears an area of the forest, plants crops for two or three seasons, and then moves on to a new area of the forest. This can lead to a slow, progressive deforestation of the area. In many parts of the world, this type of farming has increased as people move out from overcrowded cities to farm small patches of land. On the island of Java, the forest has been almost totally cleared and replaced with rice fields or plantations of such crops as rubber. Commercial farming practices, which clear even larger areas of land, can also quickly lead to rain-forest destruction.

Cattle ranching also poses a danger to rain forests. In some parts of the world, entire forests are cleared to create pastures for grazing.

Logging. In recent years, the demand for exotic woods found in the rain forest has increased dramatically. This has led to the destruction of forests in Brazil, Central America, and Malaysia, and has endangered temperate rain forests in British Columbia and Alaska. In Alaska, loggers in the Tongass National Forest have cut down more than 1 million acres (405,000 hectares) of virgin rain forest. But a federal court ruled in April 2001 that the U.S. Forest Service must consider designating more wilderness areas in the Alaskan rain forest. This decision may help to slow the rate at which trees are currently being depleted there.

Other activities. Mining, too, is a problem. Rain-forest soils can be rich in iron, bauxite (the raw material for aluminum), or other minerals, but mining operations can destroy the rain forest in the search for these minerals. Finally, wars, natural disasters, and construction projects (such as for dams and roadways) may destroy the forest.

Destruction Aftermath

The effects of rain-forest destruction are far-reaching, and in many cases are impossible for scientists to assess and to predict.

Soil and erosion. Because the soil in most rain forests is relatively infertile to begin with, once the plant layer is removed, the soil can quickly lose virtually all of its ability to support plant life. Some soils turn into a type of hard clay called laterite. Removal of a rain forest's vegetation can also lead to extensive erosion, as the soil, without plants to anchor it, is quickly washed away by rain and wind.

Flora and fauna. Destruction of the rain forests also limits biodiversity. As stated earlier, scientists believe that rain forests contain three-fourths of all the known species of plants and animals on Earth. Rain forests may also contain many species that have yet to be discovered, some of which could have medicinal value. Pharmaceutical companies are rushing to search rain forests for any undiscovered species of plants that might be useful in treating diseases.

Climate. Rain forests play a role in the world's climate. They help regulate Earth's hydrologic (water) cycle, the process whereby water that evaporates from trees and plants falls back to Earth as rain. When a forest is destroyed, the cycle is changed. The result may be droughts, floods, and soil erosion in areas that would not normally experience such events. When forests are destroyed, the ability of the surface of Earth to reflect light also changes. This, in turn, alters the patterns of rainfall, and wind and ocean currents.

Devera Pine

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