Relative air humidity at the time of burning is a key predictor of fire behaviour in the Cerrado

Background Recurrent large wildfires have become a global problem threatening human lives and assets. Extreme fire weather conditions and cured biomass increase the chances of severe and high-intensity fires that can be hard to control. The Cerrado is a tropical humid savanna with frequent, late dry season (LDS) large wildfires prevailing in protected areas. Since 2014, prescribed early dry season (EDS) fires have been applied within the integrated fire management approach. Aims To assess effects of relative humidity and fuel load on fire intensity and fuel consumption. Methods We undertook experimental fires during early and late dry seasons, during day and evening and in areas with different fuel loads. Key results We found that: (1) EDS fires under lower air relative humidity daytime conditions yielded similar fire intensities to LDS fires; (2) under higher relative humidity evening conditions, EDS fires exhibited lower intensities, which also varied with available fuels in different years. Conclusions Fire management in Cerrado landscapes should consider taking advantage of different diurnal, seasonal and fuel load conditions to address specific management objectives. Implications Acknowledging different local conditions can enhance management cost benefits.