Forests have long been regarded as one of the planet’s strongest natural defences against climate change. However, a new study has found that trees may not store as much carbon dioxide as scientists previously believed, potentially affecting future climate predictions.
Photosynthesis does not always mean growth
Researchers studied 137 forest sites across the United States and discovered that trees often stop growing months before they stop carrying out photosynthesis. While photosynthesis allows trees to absorb carbon dioxide from the atmosphere, that carbon is not always converted into wood, which stores it for decades or even centuries.
The study found that in eastern US forests, around 36 per cent of annual carbon uptake occurred after tree growth had already stopped. In California forests, the figure was about 26 per cent.
Heat and drought limit wood formation
Scientists observed that wood growth mainly occurred during periods of lower temperatures and adequate moisture. When conditions became hot and dry, tree growth slowed or stopped almost immediately, even though photosynthesis continued at a reduced rate.
Researchers warn that rising global temperatures, increasing heatwaves and prolonged droughts could further weaken forests’ ability to lock away carbon in wood.
Implications for climate models
Many climate models currently estimate forest carbon storage based largely on photosynthesis levels. The study suggests this approach may overestimate the future carbon-capturing potential of forests.
Experts say more research is needed to determine whether similar patterns occur in forests across other regions and among different tree species.
The findings highlight that while forests remain vital in tackling climate change, their long-term carbon storage capacity may be more limited than previously assumed, underlining the importance of reducing fossil fuel emissions alongside conservation efforts.