To survive during periods of drought, trees halt photosynthesis, a highly water-intensive process during which, for every molecule of CO₂ absorbed by a tree leaf, an average of around 400 water molecules are released. Entire forests then may end up emitting more CO₂ than they capture.
This is alarming given that droughts are becoming increasingly frequent and that forests play a key role in climate change mitigation policies. Although quantifying the CO₂ captured by the world’s forests remains a difficult task. It is estimated that they capture around a quarter of the CO₂ emitted by human activities.
