ICRAF presents 20 years of research on trees and water Communications Unit Ever increasing water scarcity across the world has triggered a heated debate: Does planting trees ease or worsen water shortages?
Last year, an article in the Economist, quoting research from the University of Newcastle, in Britain, and Free University in Amsterdam, argued that planting trees can exacerbate droughts.
Scientists at the World Agroforestry Centre claim that this is only one side of the story. “Trees are not bad, but it has to be the right tree in the right place,” says Prof. Chin Ong, principal scientist at ICRAF.
The Centre’s studies show that integrating trees into agricultural systems can increase the efficiency of water use, while plantations of fast-growing evergreen trees can worsen water shortages. These findings, based on 20 years of research by ICRAF in the Kenyan drylands, are part of a new policy series on the role of trees in watershed management.
Decline in rainfall
The researchers make a number of recommendations on how the water use of trees can be optimized and outline ways to minimize competition with crops.
Plantations of fast-growing evergreen trees, such as Eucalyptus or pines that consume a lot of water, should be avoided in water-scarce areas. As an alternative, scientists suggest planting deciduous trees, which shed their leaves during the dry season. In addition to consuming less water, these trees can produce a range of valuable products like timber, fruits and fodder.
Scientists also address the problem of competition for water between crops and trees. Field studies have shown that coppicing and root pruning reduces the water requirements of trees and gives crops an added advantage.
These are important lessons for the future, the scientists say, when the effects of climate change and expected decline in rainfall will make the water balance effects of trees critical to the management of agricultural landscapes across Africa.
For more information contact: Chin Ong
http://www.worldagroforestrycentre.org/water/press%20releases.asp