The relative importance of climatic, environmental, and anthropogenic factors on fire activity in Africa using the MODIS active fire product

Wildland fires are local-scale phenomena that have global-scale impacts due to emissions of greenhouse gases and aerosols. Fires are also thought to fundamentally influence ecosystem structure and function, particularly in grasslands and savannas. Satellite observations of fire events facilitate studies of the spatial distribution and frequency of fire activity, even on continental scales, and yet few studies have explored in detail the controls on such fire events. In a preliminary effort to contribute to these broad scientific issues, we integrate several sources of satellite and other spatially explicit datasets to investigate the relative importance of climate and ecosystem controls on fire activity in woody- and herbaceous-dominated biomes. Specifically, for a single year, we analyze fire occurrence in Africa--as detected by the MODIS active fire product--as a function of latitude, time of year, land-cover type, vegetation growth form, climate, and percentage C4 vegetation cover. Additionally, we integrate satellite-observed lightning activity and a spatially explicit dataset of human population density to categorize fire regimes as either human dominated (i.e., majority of ignitions are related to anthropogenic activity) or 'natural' fire ecosystems (i.e., majority of ignitions are related to lightning activity). This work will be the basis of future modeling efforts to assess the relationships among climate, fire activity, and vegetation structure, particularly in C4 grass-dominated biomes, which are thought to be dependent on regular fires for their maintenance and growth.