All was not right in the shady oak groves of northeastern Spain.

The fragrant, beloved truffles that farmers could usually find nestled deep in the roots of the trees were getting harder to find, the farmers reported to Ulf Büntgen, a scientist from the University of Cambridge. Maybe the local trees weren’t healthy, they said, or maybe something was changing in the local habitat.

Büntgen talked to farmers in Italy. Then he talked to others in France. Across the western Mediterranean he heard the same story: Something wasn’t right with the elusive, wildly valuable fungi that many small farmers relied upon for a major part of their annual income.

Büntgen is a climate scientist, and so as he kept hearing these stories