People use one-third of the plants that grow in the Amazon.

Across the world’s most famous rainforest, more than 400 Indigenous groups draw on thousands of native plants — for food, medicine, building materials and ritual. The knowledge on how to use these plants has been passed down through oral tradition, forming what researchers call a “living library.”

A new study warns that library is shrinking.

Research led by Rodrigo Cámara Leret at the University of Zurich, working with Conservation International scientist Patrick Roehrdanz, found that Amazonian peoples use at least 5,796 plant species — more than a third of the region's known flora. It's the first study to put hard numbers on how climate change threatens that body of knowledge.

The findings offer a warning: Indigenous cultures in Amazonia could lose an average of 28 to 34 percent of the plant species they use by 2080.…