Abstract
Landscape fires are substantial sources of (greenhouse) gases and aerosols. Fires in savanna landscapes represent more than half of global fire carbon emissions. Quantifying emissions from fires relies on accurate burned area, fuel load and burning efficiency data. Of these, fuel load remains the source of the largest uncertainty. In this study, we used high spatial resolution images from an Unmanned Aircraft System (UAS) mounted multispectral camera, in combination with meteorological data from the ERA-5 land dataset, to model instantaneous pre-fire above-ground biomass. We constrained our model with ground measurements taken in two locations in savanna-dominated regions in Southern Africa, one low-rainfall region (660 mm year−1) in the North-West District (Ngamiland), Botswana, and one high-rainfall region (940 mm year−1) in Niassa Province (northern Mozambique). We found that for fine surface fuel classes (live grass and dead plant litter), the model was able to reproduce measured Above-Ground Biomass (AGB) (R2 of 0.91 and 0.77 for live grass and total fine fuel, respectively) across both low and high rainfall areas. The model was less successful in representing other classes, e.g., woody debris, but in the regions considered, these are less relevant to biomass burning and make smaller contributions to total AGB.
Highlights
Landscape fires contribute to the atmospheric budgets of aerosols and elevate greenhouse gas levels
Coarse debris constitutes a small percentage of the total surface Fuel Load (FL) (Figure 9), and we found that the total fine class has the best percentage accuracy score and smallest percentage error range of any class (Table 3)
This would suggest that surface fuels that are predominantly consumed in savanna fires are the best represented by the model
Summary
Landscape fires contribute to the atmospheric budgets of aerosols and elevate greenhouse gas levels. Fires emit methane and nitrous oxide, with respective global warming potentials of 28 and 265 times greater than CO2 over 100 years [1]. The African continent plays host to a large number of these fires, and the portion of the continent in the Southern Hemisphere alone contributes almost a third of global emissions attributable to wildfires [2]. Most (>90%) come from tropical savannas, a biome where fire disturbance is recognised as affecting ecosystem structure, function and dynamics [3,4]. Savanna fires consume fuels predominantly at the ground level [5], comprising mostly grasses, leaf litter and other pieces of woody debris or dead vegetation deposited on the surface. Trees and larger shrubs are rarely affected unless the fire is intense [6,7]
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