For the past two years, scientists studying the health of forests, grasslands and swamps have been worried. Since 2023, the amount of carbon dioxide Earth鈥檚 landscapes have been able to absorb has dropped dramatically in the face of extreme weather, resulting in a record jump in atmospheric CO2 concentrations in two successive years.
But 2025 has bucked that worrying trend, with preliminary research revealing a strong rebound in the land carbon sink and a corresponding decline in the growth rate of atmospheric CO2.
Terrestrial ecosystems such as forests and grasslands take up CO2 from the atmosphere as they grow, and emit carbon when they decompose or burn. , these ecosystems have tended to absorb more CO2 than they have released, due to warmer temperatures and the fertilising effect of CO2, which boosts plant growth. This creates a global carbon sink that varies in strength from year to year.
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鈥淚n 2023 and 2024, because of El Ni帽o and the Amazon fires, we had the almost cancellation of the global land sink,鈥� says at the Climate and Environment Sciences Laboratory in France, who led the analysis. 鈥淭his cancellation led to a very high CO2 growth rate, because if CO2 is not taken by land, it stays in the atmosphere.鈥�
Ciais and his colleagues estimate that the land sink absorbed 2.36 gigatonnes of carbon in 2025. This is 0.71 gigatonnes more than the 2015-2022 average.
This recovery was driven largely by a dramatic return of growth in tropical forests. 鈥淭he climate became more normal, especially in Africa and the Amazon, so the plants recovered their carbon uptake capacity,鈥� says Ciais.
Researchers estimate that natural sinks in the oceans and on land have removed over half of the CO2 emitted by human activities. But this benefit won鈥檛 last forever, and scientists expect the world鈥檚 land biosphere to shift from being a carbon sink to a carbon source within the next several decades unless human-driven emissions taper off.
The sudden disappearance of the land sink in 2023 and 2024 had researchers worried that the sink was collapsing decades earlier than expected.
2024 was an 鈥渆xtreme year鈥�, says team member Mike O鈥橲ullivan at the University of Exeter in the UK. The 鈥渕assive recovery鈥� in 2025 is therefore good news, he says. But he warns we don鈥檛 know if this recovery effort can be sustained indefinitely, especially if weather patterns become increasingly extreme.
The super El Ni帽o already under way in the Pacific is expected to become the most intense in history later this year, bringing extreme heat and drought to crucial terrestrial sinks such as the Amazon rainforest. This means another sharp slump in carbon uptake is expected next year.
Such a cycle of repeated weather shocks, fuelled by climate change, may be weakening the global land sink鈥檚 long-term ability to store carbon, warns O鈥橲ullivan. This sink is already 25 per cent smaller than it would have been without the effects of climate change and natural variability, .
鈥淭he land is showing short-term resilience,鈥� says O鈥橲ullivan. 鈥淭here is a short-term shock, which is the El Ni帽o, and it is recovering the year after. There is strong evidence of that happening. What it doesn鈥檛 mean is that the land is going to maintain long-term resilience to climate change.鈥�
arXiv
