Landsat 8 OLI image retrieving kilometres of burned forests spread across old-growth forests in Amaz
Landsat 8 OLI (Operational Land Imager) image retrieving kilometres of burned forests (magenta colour tones) spread across old-growth forests (green colour tones) in Eastern Amazonia. White colours in the image correspond to clouds. Source: U.S. Geological Survey’s Earth Explorer Platform.

Carbon emissions from the Brazilian Amazon are increasingly dominated by forest fires during extreme droughts rather than by emissions from fires directly associated with the deforestation process, according to Stockholm Resilence Centre researcher Ana Paula Aguiar. Together with colleagues from Brazil, the UK and US, she suggests that recurrent 21st century droughts may undermine achievements in reducing emissions from deforestation in this region. Their insights were recently presented in Nature Communications.

Deforestation down, forest fires up

The authors combined multiple sources of satellite data and greenhouse gas inventories to assess drought impacts on fire incidence and associated carbon emissions between 2003 and 2015 in the Brazilian Amazon. The authors find that despite a 76% decline in (clear-cut) deforestation rates over the past 13 years (for pasture conversion, for instance), fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. They estimate that forest fires during drought years alone, contributes on average with emissions of one billion ton of CO2 annually to the atmosphere, which are more than half those from old-growth forest deforestation.

According to Luiz Aragão, lead author of the study 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 widely spread during recent droughts and how much they influence Amazonian carbon emissions. He emphasizes that, the suite of satellites currently in operation allows the retrieval of data on current climate, atmospheric carbon content and the status of terrestrial ecosystems.

"This study is important because some observations and models indicate that the intensity and frequency of droughts in Amazonia may increase as a consequence of climate change and deforestation, therefore increasing the incidence of fires," says Dr. Aragao. This can risk the stability of forest carbon stocks and undermining the biodiversity co-benefits achievable in carbon conservation schemes, such as reducing emissions from deforestation and forest degradation (REDD+).

The conclusions of the study highlight that, although Brazil has made substantive advances to report emissions from deforestation, it also needs urgently to focus on incorporating CO2 losses associated with fires unrelated to the deforestation process.

The way forward

Ana Paula Aguiar, who was also an author of the Third Brazilian Communication to the UNFCCC (one of the responsible for the greenhouse gas emission inventory for the Forest and Land use sector) and contributes in the Technical Group about REDD+ organized by the Environment Ministry, explains that the Brazilian Government has been discussing how to incorporate old-growth forest fire emissions in the official estimates.

"It was not included yet due to uncertainties that needed to be further understood, such as the actual percentage of the biomass lost in each fire event, and mainly the process of carbon uptake due to forest recovery after the fire - as they need to report net emissions, not only the gross estimates."

But the current results summed to the full body of research being conducted at INPE and partner institutions - combining field data, remote sensing and computational models - are essential to advance in this needed direction.

"The good news is that, as a result of all these efforts, soon INPE will include old-growth forest fires in their operational greenhouse emission estimates system," she says, referring to the INPE-EM system (INPE - Emission Model,, in which she and Dr. Aragao are also key contributors.

Since 2012, the system generates annual estimates of emissions of greenhouse gases derived from clear-cut deforestation and secondary vegetation dynamics, based on INPE’s monitoring systems (PRODES, TerraClass, DETER/DEGRAD).

"It is crucial that governments are aware of these values to propose realistic and effective solutions to maintain low deforestation levels, find new practices of land management and curb fire incidence. These actions will be of upmost importance for reducing future carbon emissions from the Brazilian Amazon," Aguiar and her colleagues conclude.