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Environment
Jun 13, 2026
Analyzed by GPT OSS 120B

Forests May Store Less Carbon Than Expected, New Study Finds

AI Summary
A new analysis of 137 U.S. forest sites shows that trees often cease wood growth months before photosynthesis ends, cutting the amount of carbon permanently stored. The findings challenge climate models that equate photosynthetic activity with long‑term carbon sequestration.

Researchers from Columbia University’s Lamont‑Doherty Earth Observatory discovered that trees can keep photosynthesizing after growth stops, meaning forests may lock away less carbon than many climate models predict.

Study Reveals Decoupling of Photosynthesis and Wood Growth in US Forests

The team examined 137 sites across the United States, comparing seasonal patterns of photosynthesis with actual wood formation. In both eastern forests and California, a clear lag emerged: trees halted growth well before the seasonal decline in photosynthetic activity.

Key Numbers: Site Coverage and Seasonal Growth Gaps

  • 36% of annual carbon uptake in eastern sites occurred after tree growth had stopped.
  • 26% of uptake in California sites showed the same pattern.
  • Detailed monitoring at 4 sites linked growth windows to periods of low aridity and temperature.
  • Global carbon removal totals 2.2bn tonnes CO2 per year, with land‑based actions (including tree planting) accounting for the vast majority; engineered solutions contribute only 0.1%.

Implications for Climate Models and Carbon Sink Projections

Current Earth‑system models often assume a tight coupling between photosynthesis and wood growth. The study’s authors warn that this assumption could lead to overestimates of future forest carbon sequestration, especially as rising temperatures increase heatwaves and droughts that instantly halt growth.

Future Research Directions and Policy Considerations

The researchers plan to test whether the observed decoupling holds for other species and regions. Policymakers may need to revise forest‑based carbon accounting frameworks and consider supplemental removal technologies to meet climate targets.