Today, its extensive natural resources are being exploited at phenomenal rates for subsistence living and large-scale commercial ventures by an exploding human population. At current deforestation rates - estimated at 50 acres per minute - forests that took ages to develop will be decimated in the next century.

Under a canopy of hundred-foot trees, the rain forest shelters half of all plant and animal species on earth an exuberance of wildlife unlike anything we know in temperate climates. Thousand of plant species are found nowhere else; others, familiar to us, grow in oversized versions violet plants the size of apple trees and 145-foot tall relatives of the common garden rose. Mammals, insects, and birds come in startling variations of preconceived notions of animals behavior. The unexpected rules in a place where fish eat fruit and snake "fly." Yet shifting cultivation, logging, and cattle-ranching, are destroying the rain forest forever. In the long-run, these activities are not sustainable. Why? Because, beneath the rain forest's fabulous richness usually lie soils that are surprisingly poor in nutrients. The explanation for this paradox lies in the rain forest's great age. Most jungles descend from primeval forests dating from before the Ice Ages. These forests developed on ancient land surfaces with deep layers of well-weathered soil, leached of nutrients over the ages by rainfall.

Over these impoverished soils, rain forests evolved into a highly efficient system, capturing nutrients in rainfall and rapidly recycling those in leaf fall and other decaying organic matter. Bacteria and fungi, which thrive in warm, moist conditions, reduce forest litter to basic elements, which, along with nutrients from the rainfall, are immediately taken up by a dense but shallow mat of plant roots. Very few nutrients are allowed to wash away to percolate into the soil.

The rain forest's constantly hot, humid atmosphere makes these processes possible. Under a dense canopy that moderates the heat of the sun and slows the force of strong winds, temperatures do not vary much from an average of 75 degrees. High humidity is generated by the profuse plant life, which returns much of the moisture from rainfall to the air in a process called transpiration. In fact, scientists estimate that half of the rain that falls on jungles is created by the forest itself.

It's no wonder that jungles have been called "castles built on sand." Most of the rain forest's nutrients are tied up within the luxuriant biomass and the top few inches of soil. If the forest is cut and set on fire - a widespread agricultural practice in the tropics - the initial enrichment from the burned vegetation may support crops for a few years, but any nutrients left are quickly washed away by torrential rain.