Man cannot afford to turn his back on the origins of his food supply. Both crops and livestock can become weakened by too much inbreeding. The rain forest, with its vast collection of species, can supply the genetic variety needed to fortify these plants or animals. For example, Mexican botanist Rafael Guzmán discovered a new species of grass related to modern corn. His find excited farmers because this grass (Zea diploperennis) is resistant to five of the seven major diseases that ravage crops of corn. Scientists hope to use the new species to develop a disease-resistant variety of corn.

In 1987 the Mexican government protected the mountain range where this wild corn was found. But with so much forest being destroyed, invaluable species like this one are doubtless being lost, even before they are discovered. In the forests of Southeast Asia, there are several species of wild cattle that could strengthen the breeds of domestic herds. But all these species hover on the brink of extinction because of the destruction of their habitat.

Besides being a source of food and clean air, the rain forest can be a veritable medicine cabinet. A quarter of all the drugs doctors prescribe are derived from plants that grow in tropical forests. From the cloud forests of the Andes comes quinine, for fighting malaria; from the Amazon region, curare, used as a muscle relaxant in surgery; and from Madagascar, the rosy periwinkle, whose alkaloids dramatically increase the survival rate of many leukemia patients. Despite such impressive results, only about 7 percent of all tropical plants have been screened for possible medicinal properties. And time is running out. The United States Cancer Institute warns that “the widespread elimination of the tropical moist forests could represent a serious setback to the anticancer campaign.”