The world's largest tropical rainforest has become a source of carbon for the atmosphere. Between 2010 and 2024, the Amazon released, on average, 1.17 billion metric tons of CO2 per year more than it absorbed, according to a study published in the journal Nature by researchers at Inpe, Brazil's National Institute for Space Research, with funding from Fapesp, the Sao Paulo state research foundation, and other Brazilian and international institutions.
Fire is the main driver of the imbalance. Burning emitted about 1.47 billion tons of CO2 per year over the period, almost five times the forest's estimated absorption capacity of 300 million tons a year. The work analyzed 15 years of atmospheric measurements of carbon dioxide and carbon monoxide and was led by climate scientist Luciana Gatti, head of Inpe's Greenhouse Gas Laboratory, alongside 32 other researchers.
Smoke-filled years outweigh dry years
By grouping the measured years, the team showed that human activity explains emissions better than climate. In the wetter years with less deforestation (2011 to 2014, 2017 and 2018), the average balance was 408 million tons of CO2 per year. Between 2019 and 2022, when deforestation and degradation advanced under a relatively stable climate, the figure jumped to 1.58 billion tons. In hot, dry years with intense human activity (2010, 2015, 2016, 2023 and 2024), it reached 1.8 billion tons, according to data reported by Agencia Brasil.
Climate stress still acts as an amplifier: droughts increase the carbon released by deforestation and fires. Over 46 years of data, average annual rainfall in the region fell 8%, and peak rainfall in the dry season, from August to November, dropped 20%. Average temperature rose 1.13 °C across the year and 1.81 °C in the dry season, the study found.
"The main message of the research is shocking: the Amazon's problem is human action. We are losing the forest because the region's development model has been based on destruction. We need public policies that value the standing forest," Gatti told Agencia Fapesp.
Smoke over Manaus
The scientific warning arrives in the middle of a critical fire season. Inpe has recorded more than 41,300 fire hotspots in the Amazon through October, 58% of them concentrated in September and October, against 43,100 in all of 2025. Smoke blanketed Manaus, the two-million-person capital of Amazonas state, and other municipalities, forcing school closures, overloading the health system with respiratory illnesses and prompting an environmental crime investigation over suspected deliberate burning. In Autazes, about 110 kilometers from Manaus, areas of dense forest burned this month. In Acre state, the cities of Cruzeiro do Sul and Marechal Thaumaturgo are also living under smoke.
There are signs of a response. Deforestation in the Brazilian Amazon fell 41.8% in one year, according to data reported by Agencia Brasil, and the MapBiomas monitoring project recorded the lowest forest loss in 41 years. The federal government has stepped up firefighting brigades in Para state, and illegal deforestation entered the presidential runoff debate, with candidate Flavio Bolsonaro (PL) promising to end it by 2029. For the study's authors, a drastic cut in burning, combined with zero deforestation and forest restoration, can still push back the so-called tipping point, the threshold beyond which the forest loses its ability to recover. The reversal of the Amazon's role in the carbon cycle weighs on global climate goals: without the tropical sink, the effort to contain warming grows for every country.