Cornell study: warmer climate slows forest growth, reduces carbon storage potential by up to 30%

A new study from Cornell University finds that hotter, drier conditions are slowing tree growth, which reduces the amount of carbon forests can store. Researchers used data from Swiss forests and found that current climate models may overestimate future carbon storage by as much as 30% because they assume photosynthesis equals growth. In reality, water stress limits cell division even when trees are still photosynthesizing. The study, published in Geophysical Research Letters, compared a statistical model of tree growth to a widely used land surface model. It found that broadleaf tree growth could be overestimated by a factor of 2 and coniferous by a factor of 3. This means forests, which currently absorb about 27% of human CO2 emissions, may not keep up as warming continues. Researchers say the findings highlight a gap between ecology and climate modeling. The next step is to update land models to reflect actual growth limitations, which would improve predictions of atmospheric CO2 and warming. This matters for anyone relying on nature-based carbon offsets or planning long-term climate scenarios.