Sand dunes in southern Africa are on the move, and global warming may be to blame. New research indicates that the normally stationary dunes of the Kalahari Desert are becoming more erodable, and by the end of the 21st century, stronger winds could literally blow them away. Such activity could wreak havoc on the cattle ranching and agriculture practices that rely on this land.
The susceptibility of sand dunes to climate change became apparent in the 1980's when a drought in the southwestern Kalahari Desert killed the plants that anchor the dunes. As a result, large amounts of sand became airborne and killed livestock, exacting a heavy economic toll on local farmers. When the drought stopped, the plants grew back, and the dunes stabilized. But some scientists believe global warming could "re-activate" these dunes by stressing plants, whipping up winds, and causing localized droughts.
To understand what effect climate change could have on the activity of three southern Kalahari dunefields, geomorphologist David Thomas of Oxford University in the United Kingdom and colleagues fed climate predictions into a model that yields a dune mobility index. This number classifies a dunefield as highly active, significantly active, or nonactive. When the team calculated the effect of three global climate models (GCMs)--with a range of greenhouse emission levels and different predictions for global temperature and precipitation--the result was the same: By the end of the 21st century, the entire southern Kalahari Desert dune system will be highly active--posing a major threat to the Africans who make their livings there, Thomas says.
"This is an interesting and carefully done study," says geomorphologist Dave Sauchyn of the University of Regina in Canada. But future research should investigate the effects of other climate scenarios for southern Africa, he says, as they might yield different fates for the dunes.