Drought-induced fires lead carbon emissions from Amazon forest

By Camila V. J. Silva – PhD student at Lancaster University

Since 2004 when the Action Plan for Prevention and Control of Deforestation in Amazonia forests (PPCDAm) was implemented, deforestation rates and consequently carbon emissions had fallen. However, our new study in Nature Communications showed that despite this decrease in forest loss, carbon emissions from the Brazilian Amazon are now increasingly dominated by forest fires during extreme droughts. Using satellite data and greenhouse gas inventories, we assessed drought impacts on fire incidence and associated carbon emissions between 2003 and 2015 in the Brazilian Amazon. Interestingly, while deforestation rates fell by 76% in the Brazilian Amazon between over the past 13 years, fire incidence increased by 36% only in the 2015 drought compared to the preceding 12 years.

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Spatial patterns of water deficit and active fire incidence in the Brazilian Amazon. From Aragão et al. (2018)

 

According to Luiz Aragão, the lead author of the article and a scientist from the Brazilian National Institute for Space Research (INPE): “this is the first time that scientists could clearly demonstrate how forest fires can become widespread during recent droughts and how much they influence Amazonian carbon emissions in a decadal scale”. He emphasises that, available data from satellites on current operation facilitate assessment of climate, atmospheric carbon content and the status of terrestrial ecosystems. The combination of such data allowed us to find that during the 2015 drought the ratio of active fire counts to deforestation was the largest ever, with active fires occurring over an area of 799,293 km2; and gross emissions from forest fires (989±504 Tg CO2 year-1) alone accounted for more than half of those from deforestation in old growth forests during drought years.

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Picture provided by author Jos Barlow

As the majority of climate models predict an increase of drought frequency in Amazonia in the 21st century, forests are widely susceptible to fires, particularly fragmented and degraded areas. Most forest fires start because of human activities as ignition sources and fire leakage into adjacent forests. Once spread, forest fires become out of control, sending major emissions to the atmosphere than those from deforestation, and undermines biodiversity that co-benefits from carbon conservation schemes. Our study deliver an important message to governments and political leaders from Brazil about the urgency to incorporate into estimates, COlosses associated with fires unrelated to the deforestation process. It is important to know that besides maintaining low the deforestation levels, it is crucial to think about strategies to curb fires incidence.

Carbon stock assessment on burned forests in Amazonia

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