Carbon emissions boost plant growth, which uses up more water

New Scientist : Global greening is a phenomenon in which plants are growing in places they previously weren’t because of warming temperatures and increased carbon dioxide in the atmosphere. As a result, the plants are using an increasing amount of water and drying up streams and other water sources. In Australia, Anna Ukkola of Macquarie University and her colleagues have found that stream flow has decreased by about one-quarter over the past 30 years. That is occurring because increased atmospheric CO₂ has caused plants to grow better and produce more leaves. To photosynthesize, leaves normally open pores to bring in the CO₂, which also lets water out. With more leaves, more water is released, meaning more water has to be absorbed by the roots, and at a certain point of leafiness the process results in a net loss of water. It isn’t clear whether global greening is happening in other parts of the world to the same extent and what the long-term effects are, but the phenomenon appears likely to exacerbate the spread of drought conditions in Australia.