River Levels Could Rise as More CO2 Makes Plants Less Thirsty

August 30, 2007

The UK’s Met Office has added a significant variable to the climate change equation. In a recently released study from the Hadley Center it published findings which “suggest 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 study, conducted by a team of scientists from the Met Office Hadley Centre, the University of Exeter and the Centre for Ecology & Hydrology was published in the journal Nature.

The Met Office bulletin notes that “members of the research team showed that this effect can already be seen in historical river flow records. This 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.”

Betts described the predictions as a “double-edged sword.” On one hand “increases in drought due to climate change could be less severe as plants lose less water,” but 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 (See IJ web site April 6), added that this effect also makes it more difficult to compare carbon dioxide with other greenhouse gases which do not affect plants in the same way. “We often hear about the CO2 equivalent of other gases such as methane and nitrous oxide, used in calculating carbon footprints,” he indicated. “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.”

Source: Met Office – http://www.metoffice.gov.uk

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