A collaboration between scientists and Native American tribes finds tree density in parts of the Klamath Mountains is at a record high, and at risk of serious wildfires.

Indigenous oral accounts have helped scientists to reconstruct a 3,000-year history of a large fire-prone forest in California. The results suggest that parts of the forest are denser than ever before, and are at risk of severe wildfires1. The research is part of a growing effort to combine Indigenous knowledge with other scientific data to improve understanding of ecosystem histories.