Alber Sanchez

The Amazon carbon sink is weakening as deforestation ^1–5 , rising tree mortality ^6–8 and climate change disrupt the climatic conditions that sustain a humid tropical forest ^9–11 . Forest loss reduces precipitation, increases temperatures and lengthens the dry season, driving higher carbon emissions ^1–4,11,12 . Climate stress is stronger in more deforested regions, rendering forests progressively more flammable ^1,9,13 . Large-scale climate events, such as El Niño, further amplify regional climate impacts ^9,14–17 . Here we present an analysis of 15 years of Amazonian carbon fluxes derived from atmospheric CO ₂ measurements. We determine a carbon balance of 0.32 ± 0.08 PgC yr ⁻¹ , with fires acting as the dominant source (0.40 ± 0.07 PgC yr ⁻¹ ) and forest uptake becoming increasingly unable to offset emissions. Furthermore, we investigate key drivers of the carbon emissions of Amazonia and identify three distinct year groups. Group 1 (2011–2014, 2017 and 2018) represents the role of the Amazon in the global carbon balance (0.11 ± 0.08 PgC yr ⁻¹ ) during wetter years with low human activity, such as deforestation, biomass burning and degradation. Group 2 (2019–2022) represents Amazon carbon emissions (0.43 ± 0.13 PgC yr ⁻¹ ) from human activities (mainly deforestation and degradation) during years with low climatic stress. Group 3 (2010, 2015, 2016, 2023 and 2024) has the highest carbon emissions (0.49 ± 0.07 PgC yr ⁻¹ ) and comprises warm and dry years (high climate stress), such as El Niño and the warming of the Tropical North Atlantic Ocean, associated with biomass burning.

Biomass burning plays a fundamental role in shaping landscapes and global ecosystem dynamics, with far-reaching impacts on the carbon balance, biodiversity, atmospheric composition, climate, air quality, and human health. In South America, which accounts for approximately 15% of global biomass burning emissions, accurate and accessible emission estimates are essential for long-term monitoring and for delineating policies to support neutral carbon development. We introduce the South American Biomass Burning Inventory (SAMBBI), the first open-access, continuous biomass burning emission inventory for South America, based on the regional model Brazilian Biomass Burning Emissions Model with Fire Radiative Power (BEM_FRP). SAMBBI represents a major advancement in understanding biomass burning emission dynamics and patterns by providing continuous, regularly updated emission estimates from 2003 onwards. This inventory will include emission estimates for the following species released during biomass burning: carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), and fine and coarse particulate matter (PM₂.₅ and PM₁₀). SAMBBI aims to achieve five key goals: (1) automating routines and processes to ensure continuous and standardised emission estimates; (2) ensuring the continuity and consistency of emission estimates in the post-MODIS era; (3) facilitating access to emission estimates for researchers, policymakers, and society; (4) predicting biomass burning emissions using artificial intelligence; and (5) quantifying the extent to which fire suppression in the Amazon improves air quality in the largest cities of Brazil, including the São Paulo Metropolitan Area with a population of over 20 million inhabitants. To achieve these goals, SAMBBI will (1) develop a pioneering approach to integrate data from multiple sensors, ensuring continuity in emission time series; (2) create a web platform for dashboard visualisation and seamless access to emission estimates across multiple spatial and temporal resolutions by scientists and stakeholders; (3) develop and train artificial intelligence models using environmental, climatic, and land-use predictors to forecast biomass burning emissions; and (4) conduct air quality simulations with and without Amazonian fire emissions using SAMBBI-driven inputs to quantify the urban pollution burden attributable to Amazonian fires and the potential gains from fire suppression. With these advancements, SAMBBI will constitute an innovative and accessible inventory for enhanced regional and global air pollution assessments, serving as a reference for environmental research and evidence-based policymaking.

In 2023, Brazil achieved positive environmental strides in the Amazon, with a 22% reduction in deforestation rates and a 16% decline in total fire counts compared with 2022, attributed to renewed environmental policy implementation. However, despite progress, deforestation remains above the target, and forest wildfires in old‐growth Amazonian forests surged by 152% in 2023 versus 2022, threatening biodiversity and carbon stocks. The rise in fires poses challenges for traditional farmers, impacts urban areas' air quality, and necessitates urgent measures like enhanced firefighting capabilities and long‐term strategies for fire‐free production chains to protect the Amazonian standing forests—a global socio‐environmental asset.

Biomass burning (BB) emissions negatively impact the biosphere and human lives. Orbital remote sensing and modelling are used to estimate BB emissions on regional to global scales, but these estimates are subject to errors related to the parameters, data, and methods available. For example, emission factors (mass emitted by species during BB per mass of dry matter burned) are based on land use and land cover (LULC) classifications that vary considerably across products. In this work, we evaluate how BB emissions vary in the PREP-CHEM-SRC emission estimator tool (version 1.8.3) when it is run with original LULC data from MDC12Q1 (collection 5.1) and newer LULC data from MapBiomas (collection 6.0). We compare the results using both datasets in the Brazilian Amazon and Cerrado biomes during the 2002–2020 time series. A major reallocation of emissions occurs within Brazil when using the MapBiomas product, with emissions decreasing by 788 Gg (−1.91% year⁻¹) in the Amazon and emissions increasing by 371 Gg (2.44% year⁻¹) in the Cerrado. The differences identified are mostly associated with the better capture of the deforestation process in the Amazon and forest formations in Northern Cerrado with the MapBiomas product, as emissions in forest-related LULCs decreased by 5260 Gg in the Amazon biome and increased by 1676 Gg in the Cerrado biome. This is an important improvement to PREP-CHEM-SRC, which could be considered the tool to build South America’s official BB emission inventory and to provide a basis for setting emission reduction targets and assessing the effectiveness of mitigation strategies.

The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change^1,2,3,4. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO₂ vertical profiles^5,6, deforestation⁷ and fire data⁸, as well as infraction notices related to illegal deforestation⁹. We estimate that Amazonia carbon emissions increased from a mean of 0.24 ± 0.08 PgC year⁻¹ in 2010–2018 to 0.44 ± 0.10 PgC year⁻¹ in 2019 and 0.52 ± 0.10 PgC year⁻¹ in 2020 (± uncertainty). The observed increases in deforestation were 82% and 77% (94% accuracy) and burned area were 14% and 42% in 2019 and 2020 compared with the 2010–2018 mean, respectively. We find that the numbers of notifications of infractions against flora decreased by 30% and 54% and fines paid by 74% and 89% in 2019 and 2020, respectively. Carbon losses during 2019–2020 were comparable with those of the record warm El Niño (2015–2016) without an extreme drought event. Statistical tests show that the observed differences between the 2010–2018 mean and 2019–2020 are unlikely to have arisen by chance. The changes in the carbon budget of Amazonia during 2019–2020 were mainly because of western Amazonia becoming a carbon source. Our results indicate that a decline in law enforcement led to increases in deforestation, biomass burning and forest degradation, which increased carbon emissions and enhanced drying and warming of the Amazon forests.

The Amazon Forest is a major locus for carbon and water cycling in the climate system whose function has been degraded in recent decades by land use and climate change. Most studies of Amazonia’s carbon balance have been limited by sparse sampling. We measured 742 atmospheric vertical profiles of CO2 and CO over four regions of Amazonia from 2010 through 2020. We estimate that Amazon carbon emissions increased from 0.24±0.19 PgC y-1 in 2010-18 to 0.44±0.22 in 2019 and 0.52±0.22 PgC y-1 in 2020. During these years, increases were also observed in deforestation (79% and 74%) and forest burned area (14% and 42%). Field notifications for illegal deforestation and related crimes dropped by 42%, while fines paid for judgments held fell by 89%. Carbon losses during 2019 and 2020 were comparable to losses in the record warm El Nino event of 2015-16, but this time with usual to moderate Oceanic Ninõ Index. 2020 showed 12% decrease in precipitation indicating also a climate impact in carbon emissions. The changes during 2019 and 2020 were mainly due to the western Amazonia becoming also a carbon source. We hypothesize that the consequences of the collapse in enforcement led to increase in deforestation, biomass burning and degradation producing net carbon losses and enhancing drying and warming of forest regions.