The results indicate that rising atmospheric dryness will substantially counteract the CO₂ fertilisation effect, limiting the capacity of land ecosystems to absorb carbon.
Global vegetation is close to its biological limit. Researchers project that gross primary production (GPP) will peak around the 2060s to early 2070s, increasing by only about 5.4% before entering long-term decline—signaling that the land biosphere will begin to weaken as a carbon sink within decades unless deep cuts to CO₂ and non-CO₂ greenhouse gases are made. The study also warns that growing food will become increasingly harder.
RELEVANT SUSTAINABLE GOALS
The Brake on Photosynthesis: Rising Atmospheric Dryness
The main brake is rising atmospheric dryness, measured as vapour pressure deficit (VPD), which steadily suppresses photosynthesis and increasingly cancels the fertilisation effect of elevated CO₂. The authors underscore that climate warming–induced atmospheric dryness markedly reduces terrestrial vegetation production, potentially limiting the future terrestrial carbon sink.
Tropical evergreen forests—including the Amazon—are the first to weaken. Their photosynthetic efficiency is already falling as dryness intensifies. The study cautions that most Earth system models have underestimated this effect, meaning current expectations of a strong future land carbon sink are overly optimistic. The stalled increase in GPP is more prominent in tropical regions.
Methane and Nitrous Oxide: Drying the Air Without Fertilising Plants
Methane (CH₄) and nitrous oxide (N₂O) amplify the problem. These gases warm and dry the atmosphere but, unlike CO₂, do not fertilise plant growth. By the end of the century they account for up to 29% of the rise in atmospheric dryness. In a high-emissions scenario, removing CH₄ and N₂O delays the global productivity peak by nearly a quarter of a century.
Using measurements from global eddy-covariance sites and a process-based model, the research projects that global GPP will peak mid-century and then decline. The peak increase is projected at only 5.4 ± 0.5% compared with the present, with a more pronounced stall in the tropics.
The results indicate that rising atmospheric dryness will substantially counteract the CO₂ fertilisation effect, limiting the capacity of land ecosystems to absorb carbon. The authors conclude that without deep cuts to both CO₂ and non-CO₂ greenhouse gases, the land biosphere’s carbon sink will weaken within decades, ending the era in which nature automatically buffered human emissions. The study also signals that growing food will become increasingly harder.
source of resource : Lin, S., Chen, X., Xia, J., Xin, Q., Fu, Z., He, B., Liu, Q., Piao, S., & Yuan, W. (2025). Global vegetation production may decrease in this century due to rising atmospheric dryness. Nature Ecology & Evolution. https://doi.org/doi:10.1038/s41559-025-02885-3
