Large and Increasing Biospheric Productivity of Northern Ecosystems

Plants take up carbon dioxide (CO₂) through photosynthesis. How this will change with rising CO₂ concentrations in the atmosphere will strongly determine future climate change. Yet, this is a process critically unconstrained at the global scale. An increase in the seasonal variations of atmospheric CO₂ in recent decades indicates a positive trend in photosynthetic carbon uptake and a lengthening of the growing season in northern extra-tropical ecosystems. However, the biospheric characteristics behind these changes have not yet been fully explained.

We combined data‐driven seasonal cycles of plant productivity with carbon sinks across the range predicted by current biospheric process models to explain the seasonal variations of CO₂ at high and low northern latitudes over the past 40 years. We find that increases in seasonal variations can only be explained by a larger gross primary productivity (GPP) of northern ecosystems than most current estimates, equivalent to (51 ± 2) Pg(C) a⁻¹ around 2007, and by an increase of GPP about proportional (1.1 ± 0.3) to the increase in atmospheric CO₂, also larger than most current estimates. Our results highlight the importance of the interplay between vegetation productivity and its seasonal variations, providing an improved constraint to estimate the future behaviour of the terrestrial carbon sink.

 

Reference

Cuntz M, Smith B, Canadell JG, Knauer J, and Haverd V (2025) Large and increasing biospheric productivity of northern ecosystems. Geophysical Research Letters, 52(14), e2025GL115983. https://doi.org/10.1029/2025gl115983