Aloïse Amougha clearly recalls the night 30 years ago when a spirit visited him and changed his life. “You have to plant iboga,” it instructed. “And with that iboga, you have to heal the world.”

This vision came to Amougha while he was gripped in the mystical throes of a Bwiti initiation ceremony, a traditional ritual practiced by many of Gabon's roughly 50 ethnic communities. Bwiti initiates eat or drink Tabernanthe iboga—a shrub-like tree whose roots contain a powerful psychoactive compound called ibogaine. Named after the Tsogho word “to heal,” iboga grows in several Central African countries. But its strongest cultural ties are in Gabon, where an estimated 5 percent of the country’s 2.3 million citizens practice Bwiti, and more still