A recent study out of Columbia University, led by Dr. Mukund Palat Rao, points to a gap in how climate models account for forest carbon storage and it’s worth understanding both what the finding shows and what it doesn’t.
The core idea is biological rather than political. Trees absorb CO₂ through photosynthesis continuously during the growing season. But converting that absorbed carbon into permanent wood requires the cambium a thin layer of dividing cells beneath the bark to be actively building new growth rings. That cambium activity has a narrower seasonal window than standard carbon models have assumed, and heat stress or soil moisture deficits can close that window earlier in the season. When that happens, trees continue pulling CO₂ from the atmosphere, but without active cambium division, that carbon can’t be converted to biomass. Some of it is released back through respiration instead.
The study found this “growth gap” at two research sites: roughly 36% in Eastern US deciduous forests and 26% in California’s Sierra Nevada montane forests, comparing modeled photosynthetic carbon uptake against actual wood growth.
What this means in practice is that models treating photosynthesis as a direct proxy for long-term carbon sequestration may be overestimating how much carbon forests are durably storing, particularly under increasing heat and drought stress. This has real relevance for forest-based carbon offset accounting and reforestation-dependent climate targets, since those programs typically rely on sequestration estimates built on the assumptions this research is now revising.
It’s worth being precise about scope. This is based on specific field sites and species; how broadly it generalizes to other forest types and climates is an open research question, and the paper itself frames this as motivation for refining models, not discarding the role of forests in carbon cycles. Forests still provide substantial carbon uptake, biodiversity value, and ecosystem services regardless of this finding. What’s changing is the precision of how we calculate the wood-storage component specifically.
For anyone working in carbon markets, climate policy, or forest science, this is a useful prompt to revisit baseline assumptions rather than a reason to discount forest-based climate strategies altogether.
Source: Dr. Mukund Palat Rao, Columbia University.
