The Amazon is no longer a carbon sink, it is an emitter

Long regarded as the planet’s lungs, the Amazon rainforest has for decades absorbed large amounts of human-produced carbon dioxide. A recent study, however, finds that this role has reversed: the Amazon is now releasing more CO2 to the atmosphere than it takes up. The research links this shift to widespread deforestation and forest fires, noting that in 2024 as much as 38 per cent of deforestation was caused by fire.

The work was carried out by teams of scientists who carried out direct atmospheric measurements across the basin. Using research airplanes, they sampled carbon dioxide concentrations at multiple altitudes above four Amazonian sites between 2010 and 2024. Taking measurements at different heights helps distinguish emissions coming from the forest and land surface from broader background air and allows estimation of whether an ecosystem is taking up or releasing carbon overall.

The study’s conclusion is stark: “Amazonia is a net carbon source rather than a sink and cannot offset regional anthropogenic emissions.” In plain terms, a carbon sink is any system that absorbs more carbon than it emits; a carbon source emits more than it absorbs. Anthropogenic emissions refers to greenhouse gases released by human activities. The researchers attribute the Amazon’s switch to increased tree loss and the fires that accompany clearing and degradation, which together reduce the forest’s capacity to store carbon and add CO2 directly to the atmosphere.

What this means beyond the basin is that one of the world’s largest natural absorbers of CO2 can no longer be relied on to counterbalance human-caused emissions. For countries dependent on global progress in limiting climate change, this reduces the latitude available for meeting climate goals and underscores the urgency of cutting emissions at source. The finding strengthens the rationale for policy attention to deforestation and fire management as part of broader climate strategies.

For further research, the study highlights the value of sustained, high-resolution atmospheric measurements to track changes over time and to separate natural variability from trends driven by land-use change. Continued monitoring, combined with studies of the drivers of fires and clearing, will be important to understand whether the Amazon can recover its sink function and what interventions might help. Protecting forests and reducing fires emerge as central priorities if the region is to cease being a net emitter.