Global distribution, trends and types of active fire occurrences

Fire occurrence is synonymous to terrestrial ecosystems and an important component of the Earth system. Climate change, vegetation characteristics, and human activity regulate fire occurrence and spread, however, fires also interact with them in multiple ways. Due to the complicated mechanisms of interactions between fire and land use or cover, the spatial distribution, change trends and land use or cover types of fire occurrences exist wide discrepancies in different regions or countries around the world. Therefore, the quantitative and spatial relationship and differences between fire and land use or cover at the global scale remain poorly understood systematically. Here, we combine active fire and land cover products during 2001-2020 to explore the spatio-temporal features, trends, and types of active fires from global to continental scales. Globally, the annual changes of monthly active fire occurrences kept a dramatic increase in first two or three years but a circuitous decrease since then. Most areas prevailingly experienced active fires for once to five times, a small part of areas clustered in Africa, Southeast Asia, and South America experienced active fires for over five times in the last 20-years. In particular, above 60 % of active fires (re-)occurred in forest and 20-25 % in cropland, whereas grassland and construction land only accounted for about 5 % and less than 2 % respectively. Driven by active fires, the conversion of forest to cropland accounted for nearly 60 % and the transition of cropland to forest (about 10 %) followed and formed an interactive circle. Our findings improve the understanding of fire-land cover change interactions, particularly agricultural expansion and forest loss driven by active fires. Future efforts on agricultural expansion, urban safety, carbon sequestration and biodiversity conservation should take the results of this research into account.