Ethnobotanist Mark Plotkin (born 1955) has, since the 1980s, scoured the tropical rain forests of Central and South America in search of plants with the power to heal. In his quest Plotkin has enlisted the help of the powerful shamans, or witch doctors, of the Amazon region. For Plotkin, the search has been a race against time, as more and more of the rich resources of the tropical rain forest fall to the bulldozers and land-clearing crews feverishly making way for the inexorable march of civilization.

Throughout the world, during the 20th century man's destruction of the tropical rain forest advanced at a frightening pace. According to ethnobotanist Mark Plotkin, 90 percent of the original forest cover was gone on the island of Madagascar by 2000. Matters were even worse in eastern Brazil where 98 percent of the tropical rain forest was destroyed. One area that has remained relatively untouched has been...