What it is
The Amazon's carbon sink is weakening as deforestation, rising tree mortality and climate change disrupt the climatic conditions that sustain a humid tropical forest. Forest loss reduces rainfall, raises temperatures and lengthens the dry season, driving higher carbon emissions; climate stress is stronger in more deforested regions, making forests progressively more flammable, and large-scale climate events such as El Niño amplify the regional impacts. The authors analysed 15 years of Amazonian carbon fluxes derived from atmospheric CO2 measurements. They determine a carbon balance of 0.32 ± 0.08 petagrams of carbon a year (PgC, a petagram being a billion tonnes), with fires the dominant source at 0.40 ± 0.07 PgC a year and forest uptake increasingly unable to offset emissions. Investigating the drivers of the region's carbon emissions, they identify distinct groups of years. Wetter years with little human activity such as deforestation, biomass burning and degradation (2011 to 2014, 2017 and 2018) show the Amazon's role in the global carbon balance at 0.11 ± 0.08 PgC a year. Years with low climatic stress from 2019 to 2022 show emissions from human activities, mainly deforestation and degradation, of 0.43 ± 0.13 PgC a year. Warm, dry years of high climate stress (2010, 2015, 2016, 2023 and 2024), such as El Niño years and years of Tropical North Atlantic warming, associated with biomass burning, have the highest emissions, 0.49 ± 0.07 PgC a year.
Why it matters
Across 15 years of Amazon air measurements, fires were the main carbon source, and emissions were highest in warm, dry years, at 0.49 ± 0.07 billion tonnes of carbon a year. The Amazon's carbon sink is weakening as deforestation, rising tree mortality and climate change disrupt the conditions a humid tropical forest needs. The authors find a carbon balance of 0.32 ± 0.08 billion tonnes a year, fires contributing 0.40 ± 0.07, with forest uptake increasingly unable to offset emissions. Wetter years with little deforestation, burning and degradation came to 0.11 ± 0.08; 2019 to 2022, years of low climate stress, reached 0.43 ± 0.13 from human activities, mainly deforestation and degradation.
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Filed underFire effects on ecosystems, Atmospheric and Environmental Gas Dynamics, Plant Water Relations and Carbon Dynamics