Amazon carbon emissions driven by human actions amplified by droughts.

The Amazon carbon sink is weakening as deforestation1-5, rising tree mortality6-8 and climate change disrupt the climatic conditions that sustain a humid tropical forest9-11. Forest loss reduces precipitation, increases temperatures and lengthens the dry season, driving higher carbon emissions1-4,11,12. Climate stress is stronger in more deforested regions, rendering forests progressively more flammable1,9,13. Large-scale climate events, such as El Niño, further amplify regional climate impacts9,14-17. Here we present an analysis of 15 years of Amazonian carbon fluxes derived from atmospheric CO2 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.