More CO2 makes plants less thirsty and boosts river levels

Rising carbon dioxide levels will increase river levels in the future, said the UK’s Met Office.

New research suggests that increasing carbon dioxide will cause plants to extract less water from the soil, leaving more water to drain into rivers which will add to the river flow increases already expected due to climate change.

The new study, led by Dr Richard Betts, climate impacts scientist at the Met Office Hadley Centre, shows that the effect of plant responses to carbon dioxide could be as important as those of increased rainfall due to man-made climate change.

The predictions are likely to be both good news and bad news. "It’s a double-edged sword," said Dr Betts. "It means that increases in drought due to climate change could be less severe as plants lose less water. On the other hand, if the land is saturated more often, you might expect that intense rainfall events are more likely to cause flooding".

Dr Betts, a lead author on the recent IPCC report, added: "We often hear about the CO2 equivalent of other gases such as methane and nitrous oxide, used in calculating carbon footprints. But this only accounts for the effect of these gases on global warming. If we want to compare their full impacts on droughts and flooding, we need to consider direct effects on plants too".