So diversified is its composition that researchers recently identified 179 species of trees with diameters over six inches (15 cm) on a mere two-and-a-half acres (1 ha) of land. All together, some 4,000 different species of trees grow in the forest. But so little is known about these trees and their potential that only six or seven are commercially exploited. Among the better known are sleek Brazil nut trees, mahogany, cedar and rubber trees.

In general terms, it is said that over 60,000 species of tropical plants are native to the Amazon Basin. That is nearly a quarter of all known plants. No other concentration of tropical plants on earth can match this. Even so, many thousands have never been classified.

Actually, the soil of the Amazon is thin, highly acidic and far from fertile. So how is the jungle able to sustain itself? By the so-called direct-cycle nutrient system. Around practically all the taller plants and trees there is an intricate system of surface roots. The rainwater filters through the various foliage levels and removes mineral salts from leaves, branches and tree trunks. On its way down toward the humus layer on the ground, the nutrient-rich water is partially absorbed and stored. Parasite plants, fungi and insects also play their own part in the feeding of the forest.