Earlier peak photosynthesis timing accelerates wildfire outbreak and expands burned area

Abstract The frequency and intensity of wildfires in recent decades have reached unprecedented levels1-3, raising questions about the role of vegetation phenology in driving these changes. By examining both terrestrial fire perimeters and satellite observations, we found that an earlier peak photosynthesis timing (PPT) contributes to the acceleration of wildfire outbreaks and the expansion of burned areas across the Northern Hemisphere. This correlation can be attributed to intensified drought conditions and an increased leaf supply resulting from earlier senescence. We further show that current fire-vegetation models are capable of reproducing the negative correlation between PPT and burned area, but they significantly underestimate the strength of this relationship. Our findings provide valuable insights for enhancing early wildfire detection and prediction methods by considering the feedback effects of vegetation on fire risk.