African burned area and fire carbon emissions are strongly impacted by small fires undetected by coarse resolution satellite data

Ruben Ramo*, Ekhi Roteta, Ioannis Bistinas, Dave van Wees, Aitor Bastarrika, Emilio Chuvieco, Guido R. van der Werf

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Fires are a major contributor to atmospheric budgets of greenhouse gases and aerosols, affect soils and vegetation properties, and are a key driver of land use change. Since the 1990s, global burned area (BA) estimates based on satellite observations have provided critical insights into patterns and trends of fire occurrence. However, these global BA products are based on coarse spatial-resolution sensors, which are unsuitable for detecting small fires that burn only a fraction of a satellite pixel. We estimated the relevance of those small fires by comparing a BA product generated from Sentinel-2 MSI (Multispectral Instrument) images (20-m spatial resolution) with a widely used global BA product based on Moderate Resolution Imaging Spectroradiometer (MODIS) images (500 m) focusing on sub-Saharan Africa. For the year 2016, we detected 80% more BA with Sentinel-2 images than with the MODIS product. This difference was predominately related to small fires: we observed that 2.02 Mkm2 (out of a total of 4.89 Mkm2) was burned by fires smaller than 100 ha, whereas the MODIS product only detected 0.13 million km2 BA in that fire-size class. This increase in BA subsequently resulted in increased estimates of fire emissions; we computed 31 to 101% more fire carbon emissions than current estimates based on MODIS products. We conclude that small fires are a critical driver of BA in sub-Saharan Africa and that including those small fires in emission estimates raises the contribution of biomass burning to global burdens of (greenhouse) gases and aerosols.

Original languageEnglish
Article numbere2011160118
Pages (from-to)1-7
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number9
DOIs
Publication statusPublished - 2 Mar 2021

Bibliographical note

Funding Information:
We would like to thank Niels Andela for his recommendations on characterizing fire size. This research has been financed by the European Space Agency through the FireCCI project (Contract 4000126706/19/ I-NB). R.R. was funded by the University of Alcal?'s Predoctoral Fellowship Program. G.R.v.d.W. and D.v.W. received funding from the Netherlands Organisation of Scientific Research.

Funding Information:
ACKNOWLEDGMENTS. We would like to thank Niels Andela for his recommendations on characterizing fire size. This research has been financed by the European Space Agency through the FireCCI project (Contract 4000126706/19/ I-NB). R.R. was funded by the University of Alcalá’s Predoctoral Fellowship Program. G.R.v.d.W. and D.v.W. received funding from the Netherlands Organisation of Scientific Research.

Publisher Copyright:
© This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

Keywords

  • Africa
  • Carbon emissions
  • MODIS
  • Sentinel 2
  • Small fires

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