Drought threat to terrestrial gross primary production exacerbated by wildfires

Abstract

Frequent droughts have aggravated the occurrence of wildfires and led to substantial losses in terrestrial ecosystems. However, our understanding of compound drought-wildfire events, including the hotspots, spatiotemporal patterns, trends, and their impacts on global vegetation growth, remains unclear. Utilizing satellite data on terrestrial water storage, burned areas, and gross primary production (GPP) from 2002 to 2020, we identified a positive correlation between droughts and wildfires and mapped the global patterns of compound drought-wildfire events. Approximately 38.6% of vegetated areas across the globe witnessed rise in probability of compound drought-wildfire events (< 0.016 events/10a). This increasing trend is spatially asymmetric, and greater amplification is observed across the Northern hemisphere due to frequent droughts. Furthermore, the GPP reductions induced by compound drought-wildfire events are more than twice as high as that caused by isolated droughts. These findings identify hotspots for compound drought-wildfire events and offer quantitative evidence of their greater impacts on ecosystems, aiding in the assessment of compound event risks and the implementation of future climate actions.