Tropical Forests

Tropical forests (commonly referred to as tropical rain forests) are found in a narrow band around the equatorial belt. This belt experiences a huge amount of rainfall, which averages about 80 inches and varies from 50 to 260 inches (125 to 660 centimeters) a year. The vegetation is always lush and green, with dense growth and tall trees with giant buttresses. Vines and epiphytes such as orchids and bromeliads grow in the upper canopy on larger trees to reach sunlight. On average, temperatures within the rain forest range from 68 degrees F (20 degrees C) to 93 degrees F (34 degrees C) and humidity is between 77 and 88 percent. Although rain falls throughout the whole year, there is usually a brief season with less rain, and in some monsoonal regions a substantial dry season is often experienced.

It is estimated that rain forests cover less than seven percent of the earth's surface, about the size of the United States. The forests are scattered in a few geographical regions of the world along the equatorial belt, including: The Amazon River basin in South America, by far the largest portion of the rain forest accounting for two-thirds of tropical forests; the Congo basin in Africa, with a small area in west Africa and also eastern Madagascar; in Indo-Malaysia—the west coast of India, Assam, and portions of southeast Asia; New Guinea; and Queensland in Australia.

Scientists believe that these areas contain half of the world's plant and animal species (estimated at five to 10 million). To illustrate the richness of the tropical rain forest biome, in one tree in Brazil there may be as many as 40–50 species of ants. Scientists have counted anywhere from 100 to 300 species of [Page 1774]trees in one hectare in South American rain forests. While on the (mainland) continent of Africa there is only one species of the majestic Baobab tree, in the tropical rain forest found on the island of Madagascar, there are seven different species of this tree. These forests also contain well over 95 percent of primates that are found nowhere else in the world. Scientists continue to discover new species of fauna and flora in the tropical rain forests of southeast Asia and Latin America. No one knows how many species of plants and animals are actually in the tropical rain forests. Some estimates indicate that there may be over 50 million species. Of the five to 10 million species that are suspected to be in the tropical rain forest, only six percent have been discovered, and of the six percent only a tiny proportion (about onesixth) have been intensively studied.

Tropical rain forests are fast disappearing, cut or burned for short-term profit. Tropical rain forests in South America, Africa, and southeast Asia are felled at ever-increasing rates, with thousands of hectares of pristine forests lost every year. This loss is largely blamed on conflicting economic interests for control over forests and land that has made it hard to use the forests on a sustainable basis. As a local issue, the wholesale destruction of the tropical rain forest implies the removal of an important protective cover for the soil that results in severe soil erosion, impeding forest regeneration. Soil erosion also implies the reduction in the life expectancy of the many dams that have been built throughout the tropical areas (for example, in India, the Philippines, Ecuador, Colombia, and Brazil) to generate electricity for industrialization. In places where there has been massive deforestation in upland areas, silting has reduced the life expectancy of dams downstream by half, from an estimated 50 years to only 25 years.

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