Sunday 1 March 2020

Understanding the nature of the exceptional fires in the Brazilian Amazon in 2019.

Fires in the Amazon in 2019 attracted much political and media attention, but it was not immediately clear what was burning. This is crucial to understanding impacts and identifying solutions. There are three broad types of fire in the Amazon. First, there are deforestation fires; the process of clearing primary forest which starts with the vegetation being felled and left to dry. Fire is then used to prepare the area for agriculture. Second, there are fires in areas that have been previously cleared. For example, cattle ranchers use fire to rid pastures of weeds, and smallholders, indigenous and traditional peoples use fire in farm‐fallow systems. Not all fires in previously cleared lands are intentional; some escape beyond intended limits. Third, fires can invade standing forests, either for the first time when flames are mostly restricted to the understorey, or as repeated events, resulting in more intense fires. Different types of fire have different drivers. While weak governance may lead to more deforestation fires, climate change makes forests hotter and drier, thus more likely to sustain uncontrolled fires. Different fire types also have different impacts. For example, uncontrolled fires in open lands can kill livestock and destroy crops and farm infrastructure, while even low‐intensity forest fires can kill up to 50% of the trees and reduce the value of the forests for local people. In contrast, farm‐fallow fires are essential for the food security and livelihoods of some of the Amazon's
poorest people. A failure to distinguish between different fire types has contributed to the uncertainty surrounding the recent Amazonian fires, and has important implications for policy responses.

A fire burning in the Jacunda National Forest in Rondônia State, Brazil, in 2019. Eraldo Peres/The Harvard Gazette.

In a paper published in the journal Global Change Biology on 15 November 2019, Jos Barlow of the Lancaster Environment Centre at Lancaster University, and the Universidade Federal de Lavras, Erika Berenguer, also of the Lancaster Environment Centre at Lancaster University, and of the Environmental Change Institute at the University of Oxford, Rachel Carmenta of the Department of Geography and Conservation Research Institute at the University of Cambridge, and Filipe França of the Instituto de Ciências Biológicas at the Universidade Federal do Pará, as well as some other contributors that declined authorship to maintain anonymity, evaluate the Brazilian government's claims that the Amazon fire situation in August 2019 was ‘normal’ and ‘below the historical average’ by assessing the longer term trends in active fires and annual deforestation and recent monthly deforestation trends.

The number of active fires in August 2019 was nearly three times higher than in August 2018 and the highest since 2010. There is strong evidence this increase in fire was linked to deforestation. To examine this, Barlow et al. first estimated 2019 deforestation, as the numbers from the Brazilian PRODES system for measuring annual deforestation are yet to be published. The area of deforestation detected by PRODES runs from August to July each year and is, on average, 1.54 higher than near‐real‐time DETER‐b measure of deforestation. Using this conversion factor suggests that over 10 000 km² of forest was lost in the period between August 2018 and July 2019, which would make it the highest annual loss since 2008. These annual trends are mirrored by a sharp increase in monthly deforestation detected by DETER‐b—deforestation in July 2019 was almost four times the average from the same period in 2016–2018.

The marked upturn in both active fire counts and deforestation in 2019 therefore refutes suggestions that August 2019 was a ‘normal’ fire month in the Amazon. Moreover, the increase in fires has occurred in the absence of a strong drought, which can be a good predictor of fire occurrence. The important contribution of deforestation‐related fires was consistent with media footage of large‐scale fires in deforested areas, while the enormous plumes of smoke that reached high into the atmosphere can only be explained by the combustion of large amounts of biomass. The unusual nature of 2019 was also emphasized by exceptionally high fire counts in some protected areas, such as Jamanxim National Forest where active fires increased by 355% from 2018 to 2019, 44% above the long‐term average. 

A fire burning in the Jamanxim National Forest in Para State, Brazil, in 2019. Victor Moriyama/Greenpeace.

Some key uncertainties remain. Despite the large‐scale fires seen in August 2019, there was a 35% drop in active fires in September, and it is unclear to what extent rainfall or the recent 2‐month fire moratoria declared by President Bolsonaro has contributed to this. Crucially, it is also unclear what will happen now the ban has been lifted. The figures from DETER‐b suggest deforestation remained well above average in September, despite the moratoria. Moreover, over the last 20 years, 65% of annual fire detections occur from September to December, which is the peak of the dry season for much of the Amazon. Given the essential role of fire in clearing felled vegetation, these recently deforested areas are very likely to burn at some point in the future.

Another uncertainty relates to the extent of forest fires. These are rarely detected by active fire counts, for example, active fire counts during the 2015 El Niño were unexceptional, even though forest fires burned 10 000 km² in the Santarém region and affected many other areas of the Amazon in one of the strongest El Niño‐mediated droughts on record. However, weekly mapping in August 2019 has already revealed 85 km² of forest fires in the frontier region of Brazil and Peru despite the lack of an unusual drought in 2019.

Managing Amazonian fires requires understanding what is burning, what drives contagion and extent, and how different drivers combine to make the Amazon more flammable. Tackling deforestation is key; forest clearance is a major source of ignition, and augments the flammability of remaining forests by increasing edge density, raising regional temperatures and reducing rainfall. Brazil's successful deforestation action plan of 2004–2012 provides a clear blueprint for action, but is contrary to the current government's approach of undermining forest monitoring and cutting resources for law enforcement.

An overview of fire types, drivers and their positive feedbacks on fire prevalence. Fire types are shaded by the three broad classes of fire in the Amazon: Deforestation (dark grey), fires on previously cleared lands (grey), and forest fires (light grey). Deforestation and agricultural fires are intentional, while uncontrolled fires are either started accidentally or through malevolent intent. Barlow et al. (2019).

Preventing forest fires will also require action to prevent illegal logging operations, as microclimatic changes make logged forests more flammable. Near‐real‐time monitoring and forecasting of drought intensity and fire risk would also help, especially if linked to responsive, resourced and capable local fire brigades. Global climate change is also a key driver of change in the Amazonian system, increasing both dry season lengths and temperatures. Maintaining the climate change mitigation potential of the Amazon is therefore itself dependent on reducing greenhouse gas emissions across the world.

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