Study Finds Trees May Store Less Carbon Than Climate Models Predict
A new study published in Science Advances found that oak trees stop growing months before they stop photosynthesizing, meaning increased carbon uptake does not necessarily translate into more wood growth and long-term carbon storage. Researchers analyzed 137 sites across the US, finding that 26–36% of annual carbon uptake occurred after tree growth had already ceased, with drought and heat identified as key triggers for halting growth. The findings suggest that widely used climate models, which assume photosynthesis and growth are tightly linked, may be overestimating forests' future capacity to sequester carbon.
A study led by Mukund Palat Rao of Columbia University's Lamont-Doherty Earth Observatory, published in Science Advances, challenges a core assumption in climate modeling: that photosynthesis and tree growth are closely coupled. Using satellite imagery, CO2 flux instruments, trunk sensors, and growth ring records across 137 US sites, researchers found that oak trees in the eastern US stopped growing by mid-summer but continued photosynthesizing into October, with roughly 36% of annual carbon uptake occurring after growth had ceased. At California sites, the figure was about 26%. The primary driver of this decoupling appears to be aridity and heat — when conditions become hot and dry, trees lose the internal water pressure needed for growth while photosynthesis continues at a reduced rate. Carbon absorbed after growth stops is largely directed toward foliage, metabolic maintenance, or soil microbial communities rather than long-lived woody biomass. The decoupling was most pronounced in years with high climate variability, a pattern expected to intensify with climate change. The researchers caution that Earth system models relying on photosynthesis as a proxy for carbon sequestration may therefore overestimate how much carbon forests will store in a warmer, higher-CO2 world.
Limitations & open questions
The study focuses exclusively on oak trees in the US, which limits the generalizability of the findings to worldwide carbon sink projections. Additionally, the precise quantitative impact on existing Earth system model projections — i.e., by how much forests' carbon sequestration capacity might be overestimated — is not provided.
How coverage differed
Both outlets reported the core findings consistently, but The Guardian added broader policy context — including a recent report on carbon removal technologies and the scale of land-based carbon removal efforts globally — framing the study within ongoing debates about climate mitigation strategies, while Mirage News stayed closer to the scientific methodology and researcher quotes.
What different sources said
Trees may store less planet-heating carbon than hoped, study suggests
- Mirage NewsCenter
Research: Future Trees May Store Less Carbon Than Expected
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