Chapter One

Forests of the World

Ring of Rainforests

Where in the world are rainforests? Tropical rainforests ring the earth in a narrow band centered about the equator. They are found in Latin America, Asia, and Africa.¹ More than one-half of the world's intact tropical forests are found in three countries: Brazil, the Democratic Republic of the Congo (formerly Zaire), and Indonesia. The largest continuous rainforest lies in South America, where about 2.7 million square miles (6.9 million square kilometers) of forest cover the Amazon Basin.

Does the United States have tropical rainforests? Certainly we have our share of dense, biologically rich forests. Along the Pacific Coast in the United States, extensive forests flourish in the rain and fog. Douglas fir, sitka spruce, and hemlock form vast forests. But because the air stays cool for much of the year due to the northerly location, these forests are temperate rainforests, not tropical ones.

Tropical rainforests are aptly named, since they receive rainfall for three to four hours every day during extended rainy seasons. These spectacular forests contain more than half of all the plant and animal life on the planet. People live and work in these rainforests.

Not all tropical forests are wet. Some tropical forests receive less rainfall, and are classified as dry tropical forests. Dry forests account for a little more than half of all tropical forests. In these materials, we will talk mostly about tropical rainforests.

1 Tropical rainforests of the world. Tropical moist forests are found in Latin America, Asia, Africa, and small areas of Australia. Source: Adapted from Smithsonian Institution, 1988.

The Wonders of Tropical Rainforests

Tropical rainforests don't look like the forests we have in this country. In addition to the three layers (canopy, understory, and forest floor) found in forests here, they have an emergent layer with enormous trees that tower above the forest. Plants known as epiphytes cover the branches of canopy trees. (Epiphytes are plants that get nutrients and water from the air and from rain rather than from soil. They use other plants for support.) 90 percent of all of the organisms found in the rainforest live in the canopy, where sunlight is most accessible. The dimly lit understory of a tropical rainforest harbors plants such as philodendrons and zebra plants, that often become houseplants in U.S. homes. The forest floor is covered with a thin layer of fallen leaves, seeds, fruits, and branches that very quickly decompose. The soil on the floor is often infertile, washed of nutrients by constant rains.

These layers and nooks and crannies give structure to the tropical rainforest. Tropical islands, mountaintops, valleys, and other areas provide unique small habitats found nowhere else in the world.

Why Are the Tropical Rainforests Being Deforested?

Tropical forests may be unique and diverse, but they also are being lost at a rapid rate. Large areas are being deforested, and stripped of their cover. Trees are felled and land is burned to prepare soil for crops, grazing, or other uses. Deforestation has a devastating impact. Soils lose nutrients, animal and plant species risk extinction, and changes in world climates may even be triggered.

Tropical forest loss has increased in just the past decade. Tropical forests today cover some 3.7 to 4 billion acres, (1.5 to 1.6 billion hectares) or about 10.4 percent of the earth's land. Up to 40 percent of the tropical forests have been lost over the centuries, with much of that loss in the past 40 to 50 years.

Forest Change in the United States

What's happening to tropical rainforests today can be compared to the loss of U.S. forests during the early years of European settlement. During the 1700s and 1800s, much forest land in the United States was converted to cropland and pasture to produce food for a growing population.

Since about 1920, however, the area of forest land in the U.S. has stabilized, and even slightly increased. This is due mostly to improvements in crop yields and mechanization, which reduced the amount of land needed to feed people.

It would be nice to be able to say tropical rainforests will be saved once human needs for food are met. However, the world population surpassed the 6 billion mark in early 1999 and is clearly headed for much higher levels. Much of the growth in human numbers will be in the world's tropical regions. As more people try to meet their needs in these regions, tropical forests will be under increasing pressure.

Forests now cover 32 percent of the land area of the United States, compared to about 50 percent at the time of European settlement. Source: MacCleery, Douglas W. 1992.