Earlier peak photosynthesis timing escalates global wildfires

Abstract

More intense fire weather due to climate change is implicated as a key driver of recent increases in regional wildfire activity. As fuel stocks, the roles of vegetation itself and its phenology change in wildfire dynamics, however, are not fully appreciated. Using long-term satellite-based burned areas and photosynthesis observations, we reveal that an earlier peak photosynthesis timing (PPT) acts to escalate wildfires, with an increase in the global average burned fraction by 0.021% (~2.20 Mha) for every additional day of PPT advancement. Satellite observations and the Earth System modeling consistently show that this fire escalation is due to intensified drought conditions and increased fuel availability associated with earlier PPT. Current fire-enabled dynamic global vegetation models can reproduce the observed negative correlation between PPT and burned area but underestimate the strength of the relationship notably. Given the continued PPT advancement owing to climate change, the bioclimatic effects of vegetation phenology change suggest a pervasive upward pressure on future wildfires.