The Conversation had reported on a paper published in Nature Communication this month reports that plants are responding to increased CO₂ in the atmosphere by taking up more CO₂ than they did thirty years ago. The interesting thing about this study is that the increased CO₂ uptake is not at the expense of increased water use.
Increasing carbon uptake typically comes at a cost. To let in CO₂, plants have to open stomata in their leaves, which in turn allows water out (called evapotranspiration). The study showed that the rate of evapotranspiration stayed relatively constant, while the CO₂ uptake had increased by 17%.
The plants appear to have adapted a mechanism to allow CO₂ uptake while minimising water loss.
The ratio of carbon uptake to water loss by ecosystems is called ‘water use efficiency’ and it seems that plants are becoming more water efficient