Recent trends in African fires driven by cropland expansion and El Nino to La Nina transition

Landscape fires are key in African ecosystems(1-3) and the continent is responsible for similar to 70% of global burned area and similar to 50% of fire-related carbon emissions(4,5). Fires are mostly human ignited, but precipitation patterns govern when and where fires can occur(6). The relative role of humans and precipitation in driving the spatio-temporal variability in burned area is not fully disentangled but is required to predict future burned area(7,8). Over 2001-2012, observations indicate strong but opposing trends in the African hemispheres(4). Here we use satellite data and statistical modelling and show that changes in precipitation, driven by the El Nino/Southern Oscillation (ENSO), which changed from El Nino to La Nina dominance over our study period, contributed substantially (51%) to the upward trend over southern Africa. This also contributed to the downward trend over northern Africa (24%), but here rapid demographic and socio-economic changes were almost as important (20%), mainly due to conversion of savannah into cropland, muting burned area. Given the economic perspective of Africa and the oscillative nature of ENSO, future African savannah burned area will probably decline. Combined with increasing global forest fire activity due to climate change(9-11), our results indicate a potential shift in global pyrogeography from being savannah dominated to being forest dominated.