Study: Trees may store less carbon than previously estimated, challenging climate models

A new study of 137 forest sites across the United States found that trees often stop growing months before they stop photosynthesis. This means carbon absorbed from the atmosphere is not always converted into wood, where it would be stored for decades. In eastern U.S. forests, about 36% of annual carbon uptake occurred after growth had already stopped. In California, the figure was around 26%. The research suggests that heat and drought limit wood formation, even when photosynthesis continues at a reduced rate. As global temperatures rise and heatwaves become more frequent, forests may lock away less carbon than current climate models assume. Many models estimate carbon storage based on photosynthesis levels, which could overstate the future carbon-capturing potential of forests. The findings do not diminish the importance of forests in fighting climate change, but they highlight the need to reduce fossil fuel emissions alongside conservation. More research is needed to see if similar patterns occur in other regions and tree species.