What shapes fire size and spread in African savannahs?

Abstract

Fires play an important role in savannah ecosystems, shaping among other things vegetation structure and altering species composition. As direct and indirect anthropogenic pressures on these ecosystems increase, fire dynamics in savannahs are expected to change in the coming decades, with potential impacts on ecosystem functioning. Although the ecological impacts of fires are relatively well-known, the factors that shape fire dynamics in these ecosystems have received less research attention. Using Pendjari National Park (Benin) as a case study, we assessed the importance of different biotic and abiotic factors in shaping fire size and spread in the region. Our results show that fires spread faster (1) in the middle of the dry season compared to the early or late dry season, (2) in areas that are far away from natural and anthropogenic firebreaks, and (3) in areas that are covered with highly flammable vegetation. By contrast, most vegetation types had little influence on fire size, which seems to depend instead on rainfall. Our approach and results highlight new avenues for satellite data to improve our understanding of fire dynamics in large, remote savannah ecosystems and to improve our ability to predict how fires spread, a key variable for wildlife management in the face of rapidly changing environmental conditions.