Refined burned-area mapping protocol using Sentinel-2 data increases estimate of 2019 Indonesian burning

Abstract. Like many tropical forest nations, Indonesia is challenged by landscape fires. A confident understanding of the area and distribution of burning is crucial to understanding the implications of these fires and how they might best be reduced. Given uncertainties surrounding different burned-area estimates, and the substantial differences that arise using different approaches, the accuracy, and merits of such estimates require formal examination. Despite investment in fire mitigation measures since the severe El-Nino 2015 fire season, severe burning struck Indonesia again in late 2019. Here, drawing on Sentinel-2 satellite time-series analysis, we present and validate new 2019 burned-area estimates for Indonesia. The corresponding burned-area map is available at: https://doi.org/10.5281/zenodo.4551243 . We show that > 3.11 million hectares (Mha) burned in 2019, 31 % of which on peatlands. This burned-area extent is double the Landsat-derived Official estimate of 1.64 Mha from the Indonesian Ministry of Environment and Forestry, and 50 % more that the MODIS MCD64A1 burned-area estimate of 2.03 Mha. It has greater reliability as these alternatives, attaining a user’s accuracy of 97.9 % (CI: 97.1 %–98.8 %) compared to 95.1 % (CI: 93.5 %–96.7 %) and 76 % (CI: 73.3 %–78.7 %), respectively. It omits fewer burned areas, particularly smaller- (