Spatiotemporal changes in global cropland fire activity from 2003 to 2020

Agricultural straw burning is a significant source of greenhouse gas emissions, adversely affecting regional human health and air quality. Understanding the spatiotemporal patterns of agricultural fires is crucial for developing effective emissions reduction strategies in cropland to mitigate climate change. Although it is reported that cropland fires have been decreasing over the past two decades, the trends of global cropland fires on seasonal and diurnal scales remain poorly quantified, limiting a complete understanding of their spatiotemporal dynamics. This study analyzes global cropland fire activity from 2003 to 2020 at annual, seasonal, and diurnal scales, using multiple satellite-based burned area datasets, active fire products, and cropland classification datasets. The results show that from 2003 to 2020, global cropland burned area, active fire detections, and fire intensity all exhibited significant decreasing trends (p < 0.05), with relative changes of -43.5%, -30.3%, and -3.5%, respectively. The most significant decreases in cropland burned area and active fire detections occurred in Africa, while the largest decline in fire intensity was observed in Asia. Moreover, cropland fire activity displayed notable seasonal and diurnal variations. On the seasonal scale, the largest declines in cropland burned area, active fire detections, and fire intensity were observed in December, August, and November, respectively. Notably, fire intensity showed a significant increasing trend (p < 0.05) in April and September. On the diurnal scale, the decrease in cropland active fire detections was primarily driven by daytime activity; however, the rate of decline in fire intensity at night was about 1.5 times that during the day. These findings offer valuable insights into the comprehensive spatiotemporal patterns of global cropland fires, providing a foundation for more effective cropland management and carbon mitigation strategies.