Science - January 24, 2008

World faces prospect of drought

The soil is drying out in an increasing number of countries. According to model calculations made by Dr Justin Sheffield, drought will increase throughout the world in the next hundred years

Justin Sheffield predicts in his PhD thesis that the area of the world affected by drought will double in the next hundred years.
Sheffield’s simulations predict that the area of drought-ridden regions in the world will double in the coming century. Hardest hit will be the Mediterranean, Central America and southern Africa, where soils will deteriorate considerably.

Up to now West Africa is the area that has faced the most serious droughts, whereas many other parts of the world have had increasing amounts of rainfall. But even the wettest places have seen change in recent years, according to Sheffield’s analysis. The rising temperatures seem to have broken the prevailing pattern of rain in the last ten years. As a result, more countries are experiencing periods of drought.

In the future scenarios that Sheffield sketches, the drought trend looks set to continue through the coming century as a result of temperature rises. But not only will more parts of the world face periods of drought; the droughts will also be more serious in many areas. In addition, Sheffield expects that both short and long periods of drought will occur more frequently.

This will have serious consequences for the moisture stored in the soil and therefore for agriculture and water availability. How quickly soils will dry out is difficult to say for certain, according to Sheffield. At regional level he expects that the increase in drought will be gradual and that changes will therefore not be immediately noticeable. / Laurien Holtjer

Justin Sheffield received his PhD on 15 January. His promotor was Professor Peter Troch, former Professor of Hydrology and Quantitative Water Management at Wageningen University, now at the University of Arizona, USA.