From 2010 to 2024, the Amazon rainforest – the largest tropical rainforest on the planet – released an average of 1.17 billion metric tons more carbon dioxide (CO 2 ) into the atmosphere than it absorbed each year. Wildfires were the main source, emitting approximately 1.47 billion metric tons of CO 2 per year – far exceeding the forest’s absorption capacity of 300 million metric tons per year.
This information comes from a study published on October 21 in Nature , considered one of the world’s most important scientific journals. Led by scientists from Brazil’s National Institute for Space Research (INPE), the study received funding from FAPESP and other national and international institutions.
Based on an analysis of 15 years of measurements of atmospheric carbon, the primary greenhouse gas, the study identified human activities as the factor responsible for this imbalance. Therefore, the study emphasizes the need for a drastic reduction in wildfires, combined with zero deforestation and forest restoration, to prevent the forest from reaching a tipping point – a threshold beyond which it loses its ability to sustain itself and recover, giving way to other types of vegetation.
This warning is particularly important given that the number of wildfires in the Brazilian Amazon is approaching the total for 2025. According to INPE data , there have been more than 41,200 recorded fires in less than ten months (58% of which occurred in September and October), compared to 43,130 fires for all of last year. Dense smoke has blanketed municipalities in the state of Amazonas, especially the capital city of Manaus. This has led to the suspension of classes, an overload of the healthcare system due to respiratory problems, and an investigation into environmental crime with suspicion of deliberate human action.
“The main message of the study is shocking: the problem in the Amazon is human activity. We’re losing the forest because the region’s development model has been based on destruction. We need public policies that value the standing forest,” says Luciana Vanni Gatti , climate scientist, coordinator of INPE’s Greenhouse Gas Laboratory (LaGEE), and lead author of the article.
In addition to identifying factors associated with emissions, the study highlights changes in the region’s climate conditions over the decades. By analyzing data from the past 46 years, the scientists found that deforestation and degradation in the Amazon have reduced annual precipitation by 8% and by 20% during the peak of the dry season (between August and October). During the same period, the average annual temperature increased by 1.13°C, and by 1.81°C during the dry season.
According to Gatti, these changes compromise the conditions necessary for the rainforest’s survival. They contribute to a feedback loop in which the loss of vegetation reduces rainfall and raises temperatures. This leads to further fires and accelerates the degradation of the remaining forest. “It places enormous stress on the remaining forest,” the researcher told Agência FAPESP .
The impact of human activities
The scientists compared periods with different climatic conditions and levels of human intervention. They grouped the years into three scenarios. The data were divided into three groups: 1) rainy years (2011, 2012, 2013, 2014, 2017, and 2018) with low levels of human activity; 2) years with low climate stress (between 2019 and 2022) and high rates of deforestation (97% increase) and wildfires (25% increase); and 3) hot and dry years (2010, 2015, 2016, 2023, and 2024) during which phenomena such as El Niño and the warming of the North Tropical Atlantic had an impact. This was associated with a sharp increase in wildfires (92%).
The results showed that, on average, the Amazon shifted from being a CO 2 sink to a CO 2 source during the years in groups 2 and 3. This occurred due to a surplus of emissions in the “carbon balance,” which considers all absorption and release processes, whether natural or human-induced.
In group 2, emissions were nearly four times higher than in group 1, reaching an average balance equivalent to approximately 1.58 billion metric tons of CO 2 per year. Group 3 had the highest value, with an average balance of 1.8 billion metric tons of CO 2 per year.
A region’s carbon balance can be altered by natural and human-induced factors, including the burning of fossil fuels such as oil, natural gas, and coal. However, plant photosynthesis is the process that contributes to the removal of significant amounts of atmospheric CO 2 and is essential for the growth and survival of vegetation.
For this reason, forests are considered major carbon sinks. The carbon is released back into the atmosphere when this vegetation dies or decomposes slowly. Forest fires also abruptly and immediately release the CO 2 present in plant biomass.
After accounting for emissions from fires, the Amazon absorbed nearly the same amount of CO 2 as it released back into the atmosphere in the three groups of years analyzed. This left the biome’s “net biome exchange” (NBE) close to neutral. Consequently, little to no CO 2 was absorbed to offset the greenhouse gases released by the fires, highlighting the significant impact of human activities on this imbalance.
“Were it not for La Niña, emissions in group 2 years could have been even worse. Thanks to that phenomenon, the Amazon’s carbon absorption during the rainy season offset 75% of the emissions during the dry season,” Gatti explains.
Unlike El Niño, La Niña occurs when the equatorial waters of the Pacific Ocean cool to at least 0.5°C below the historical average. These cycles typically last nine to 12 months and occur every two to seven years. This triggers a series of climatic effects across the planet. In Brazil, for example, it leads to reduced rainfall in the South and increased precipitation in the North and Northeast.
Between 2020 and 2023, the so-called “triple dip” of La Niña occurred for the first time in more than two decades. This consists of the persistence of abnormal cooling in the Pacific for three consecutive Southern Hemisphere summers.
Knowledge gained over the years
To arrive at these results, the group used data collected from 2010 to 2024 through flights in small aircraft and the quantification of CO 2 and carbon monoxide (CO) at INPE’s Greenhouse Gas Laboratory. Samples were collected at four locations to cover all regions of the Amazon: northeast, southeast, southwest, and northwest.
The analysis also combined carbon measurements with data on deforestation, wildfires, precipitation, air temperature, and sea surface temperature.
This methodology, based on carbon balance data collected since 2010, has also resulted in three other articles led by Gatti and published in Nature : one in 2014 , one in 2021 , and one in 2023 . The two most recent studies indicated that the biome was becoming a carbon source, particularly in more deforested regions.
In addition to these impacts, scientific literature shows that the Amazon is experiencing more frequent periods of extreme drought and heat waves. For example, one study , detected an increase of more than 3°C in maximum temperatures during the dry season, even in preserved areas. Another study revealed that the extreme drought and heat of the last El Niño could become the “new normal” in tropical forests if greenhouse gas emissions are not reduced ( read at: agencia.fapesp.br/59339 ).
“We see the forest absorbing less and less carbon. But the question is, is this happening because the vegetation is photosynthesizing less or decomposing more? Furthermore, are human activities exceeding that capacity, or is it a combination of all those factors? Answering those questions is extremely important to determine whether the trees are losing their ability to continue living in that environment,” Gatti points out.
According to the researcher, the group has been working on a new phase since 2022 to make progress on this issue. They have been analyzing data related to carbonyl sulfide (COS), a chemical variant of CO 2 . COS acts as an atmospheric tracer of photosynthesis, a kind of molecular marker that allows for more precise measurement of photosynthesis and helps find answers to the questions raised by Gatti.
The study received support from FAPESP through the Research Program on Global Climate Change (projects 16/02018-2 , 11/51841-0 , and 08/58120-3 ) and a scholarship to INPE researcher Camilla Lima Cunha , one of the authors of the article.
Cunha highlights the importance of ongoing funding to enable the long-term research needed to understand the mechanisms that impact tropical forests. “Ongoing investment in science is essential to understanding the transformations underway in the Amazon and identifying the factors that compromise its ability to absorb carbon. That knowledge is essential for deepening our understanding of environmental changes, as well as for informing decision-making and defining forest conservation strategies,” says the researcher.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
Nature
Amazon carbon emissions driven by human actions amplified by droughts
21-Oct-2026