Quantifying immediate carbon emissions from El Nino-mediated wildfires in humid tropical forests

Withey, Kieran and Berenguer, Erika and Palmeira, Alessandro Ferraz and Espirito-Santo, Fernando D. B. and Lennox, Gareth D. and Silva, Camila V. J. and Aragao, Luiz E. O. C. and Ferreira, Joice and Franca, Filipe and Malhi, Yadvinder and Rossi, Liana Chesini and Barlow, Jos (2018) Quantifying immediate carbon emissions from El Nino-mediated wildfires in humid tropical forests. Philosophical Transactions of the Royal Society B: Biological Sciences, 373 (1760). ISSN 0962-8436

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Abstract

Wildfires produce substantial CO2 emissions in the humid tropics during El Niño-mediated extreme droughts, and these emissions are expected to increase in coming decades. Immediate carbon emissions from uncontrolled wildfires in human-modified tropical forests can be considerable owing to high necromass fuel loads. Yet, data on necromass combustion during wildfires are severely lacking. Here, we evaluated necromass carbon stocks before and after the 2015–2016 El Niño in Amazonian forests distributed along a gradient of prior human disturbance. We then used Landsat-derived burn scars to extrapolate regional immediate wildfire CO2 emissions during the 2015–2016 El Niño. Before the El Niño, necromass stocks varied significantly with respect to prior disturbance and were largest in undisturbed primary forests (30.2 ± 2.1 Mg ha−1, mean ± s.e.) and smallest in secondary forests (15.6 ± 3.0 Mg ha−1). However, neither prior disturbance nor our proxy of fire intensity (median char height) explained necromass losses due to wildfires. In our 6.5 million hectare (6.5 Mha) study region, almost 1 Mha of primary (disturbed and undisturbed) and 20 000 ha of secondary forest burned during the 2015–2016 El Niño. Covering less than 0.2% of Brazilian Amazonia, these wildfires resulted in expected immediate CO2 emissions of approximately 30 Tg, three to four times greater than comparable estimates from global fire emissions databases. Uncontrolled understorey wildfires in humid tropical forests during extreme droughts are a large and poorly quantified source of CO2 emissions. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Item Type:
Journal Article
Journal or Publication Title:
Philosophical Transactions of the Royal Society B: Biological Sciences
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1300
Subjects:
ID Code:
128976
Deposited By:
Deposited On:
15 Nov 2018 16:20
Refereed?:
Yes
Published?:
Published
Last Modified:
26 Sep 2020 05:40