CRISIS IN THE RAIN FOREST

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Time is running out for the most valuable bioregion on the planet.

By David Schoonmaker

Imagine a place where it's dusk at noon, where the temperature seldom varies from 80°F and the humidity is always close to 100%. You stand on a spongy mat of decaying leaves that few plants penetrate. Massive roots lying on the ground gather to buttress tree trunks that vanish into a leafy canopy at least 30 feet above. As open as it is at ground level, the foliage layer overhead is so dense that less than 3% of the sunlight falling on the treetops 150 feet above filters to the forest floor. But for the occasional piercing calls of birds, there's scant evidence of animal life. Little would you guess that this is home to half the species on our planet.

Misconceptions abound about what a rain forest is and what value it has. To people of temperate climates, the tropical rain forest is mysterious, alien. Hollywood images are threatening: thick, viper-and vermin-ridden undergrowth accessible only to sweating, machete-wielding persons of limited (and often diminishing) sanity. As a result, rain forest too often is taken to mean jungle.

The Earth's Greenbelt

Tropical forests are no more monolithic than they are jungles. Botanists subdivide them into 30 or 40 categories, but we can probably get by if we stretch the term tropical rain forest to include woodlands that get over 80 inches of rainfall per year and are close enough to the equator to be so unaffected by seasons that all the trees are evergreen.

Virgin tropical rain forests wrap around the equator, covering about 1,500,000 square miles. Almost 60% are located in the Amazonian regions of Brazil, Peru, Colombia, Bolivia and Venezuela, but there are other significant stands in Indonesia, Zaire, Papau-New Guinea and Burma.

For hundreds of millions of years, tropical rain forests have protected life-forms against the vagaries of climate—serving as Earth's safe-deposit boxes of biological diversity. They have grown and shrunk with the eons, they have been divided by the parting of the continents, and different areas have evolved separately. But threads can be tied from current residents to species of the early Cretaceous period, 140 million years ago.

Perhaps as a result of their long-term stability, rain forests contain an incredible variety of different plants and animals. While covering only about 2% of the world's land area, they harbor over half our planet's roughly 10 million species. In the Amazon alone, there are more than 50,000 species of plants and 3,000 offish. The whole of North America has only about 17,000 plant species and Europe has only 300 different types of fish. Costa Rica alone is home to 103 species of bats; all of North America, 40.