Abstract
Wildfires can destroy property and vegetation, thereby threatening people’s livelihoods and food security. Soil moisture and biomass are important determinants of wildfire hazard. Corresponding novel satellite-based observations therefore present an opportunity to better understand these disasters globally and across different climate regions. We sampled 9,840 large wildfire events from around the globe, between 2001 and 2018, along with respective surface soil moisture and biomass data. Using composites across fire events in similar climate regions, we show contrasting soil moisture anomalies in space and time preceding large wildfires. In arid regions, wetter-than-average soils facilitate sufficient biomass growth required to fuel large fires. In contrast, in humid regions, fires are typically preceded by dry soil moisture anomalies, which create suitable ignition conditions and flammability in an otherwise too wet environment. In both regions, soil moisture anomalies continuously decrease in the months prior to fire occurrence, often from above-normal to below-normal. These signals are most pronounced in sparsely populated areas with low human influence, and for larger fires. Resolving natural soil moisture–fire interactions supports fire modelling and facilitates improved fire predictions and early warning.
Highlights
Wildfires can destroy property and vegetation, thereby threatening people’s livelihoods and food security
In order to identify a physical link between the soil moisture patterns and fire occurrences, we employ vegetation optical depth (VOD) as a proxy for vegetation biomass[31]
The lower fire occurrence in the Mediterranean compared to similar climate regions such as western North America is due to the exclusion of highly populated areas, which implies different regional land uses[32]
Summary
Wildfires can destroy property and vegetation, thereby threatening people’s livelihoods and food security. While fires can be ignited by humans or lightning[1,15], climate influences the possible fire spread and s ize[16,17], and the potential implications of wildfires[18] In this context, soil moisture has been identified as a key variable for understanding and predicting wildfire hazard[1,19,20,21,22]. Benefitting from recent advances in the satellite-based derivation of surface soil moisture, we perform a global analysis of the role of soil moisture in the occurrence of large wildfires This allows us to explore potential differences in pre-fire soil moisture conditions across cold and warm, as well as humid and arid regions. This approach allows the exclusion of areas where human-made infrastructure covers significant space, and where human fire suppression obscures natural soil moisture–fire interactions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
