The United Kingdom’s Forestry Research Programme has discovered that planting trees can decrease the amount of available surface water, helping desertification instead of reducing it, reports Fred Pearce of New Scientist. The report says that in some places planting more trees follows the conventional wisdom that trees help prevent floods and store water.
However, in other places the planted trees can actually lower water tables and make areas increasingly dry. The growth of alien pine and eucalyptus trees in South Africa was cited in the report, where the trees are thought to cut river flow by three percent.
Findings from India where fields were converted to forests saw water yields drop by over 15 percent. Ian Calder from the University of Newcastle says, “We’re not saying they never produce water benefits or that they don’t have an important role in the ecosystem, but if we are trying to manage water resources effectively, the simple view that more trees are always better is bad policy.”