Photographs by Manon van Vark in Surinam

Drug companies are returning to the Earth's forests in their search for new medicines in a practice known as bioprospecting.

An isolated Amerindian tribe in Surinam, the Trio, has drawn up a contract with an American environmental organisation to collect plant samples for medicinal research.

The tribe's shaman can help the collectors find the best plants suitable for medicinal use.

Shaman still rely on the medicinal plants to treat injuries.

With few shamen left in the village, children are been taught basic plant knowledge at school.

The Trio tribe were converted to Christianity by American missionaries 30 years ago. But their lifestyle is still traditional, with cassava as their staple food.