A new study published in Science Advances challenges a key assumption in climate models: that tree growth and photosynthesis happen in lockstep. Researchers found that oak trees on the U.S. East Coast and in California stopped growing woody biomass by mid-summer, even as they continued to absorb CO2. The oaks absorbed 36% and 26% of their carbon without growing, respectively, suggesting that forests may store less carbon over the long term than previously estimated. The findings have direct implications for carbon offset projects that rely on afforestation and reforestation. If trees convert less absorbed CO2 into durable wood than models assume, the carbon storage value of new forests could be overstated. The study also adds to evidence that hot, dry conditions limit growth, which could worsen as the climate warms. Researchers are now studying whether this growth-photosynthesis decoupling occurs in other species and ecosystems.
