One of the first studies to examine how climate change might alter the land surface of Africa has been published by scientists from Oxford University.
Changes in precipitation and faster winds will "activate" the dunes
Their research details how the immense dunefields of the Kalahari could be stirred up by global warming.
The investigation, reported in the journal Nature, warns that large areas of currently productive land could become engulfed by shifting sands.
"The social consequences of these changes could be drastic," they say.
The team, led by Professor David Thomas, urges politicians in the region not to pursue development policies that might exacerbate the coming problems, turning currently semi-arid areas into desert.
"We've seen in Botswana, for example, with European Union support, an enormous growth in livestock production using groundwater. That in itself has put great pressure on the Botswana landscape," Professor Thomas told BBC News.
"[The shifting sands] will make those Western-sponsored programmes very unsuccessful into the future."
The Oxford team took data from three different computer models that are used to forecast likely climate change over the course of the next century.
The scientists ran this information through their own simulator, which has been specifically tuned to the dynamics of the Kalahari dunefields.
These dunes punctuate 2.5 million sq km of Africa - from the northern end of South Africa, right up through Angola, Botswana and Namibia, to western Zimbabwe and western Zambia.
They were built up thousands of years ago and are now reasonably well covered by vegetation.
But Professor Thomas and colleagues found that no matter which general climate model data they used, their simulator came out with projections for dramatic increases in dune "activity" - they will start to erode and move as precipitation falls and wind speeds increase.
The southern dunefields of Botswana and Namibia become activated by 2040, while the more northerly and easterly dunes in Angola, Zimbabwe and Zambia begin to shift significantly by 2070.
By the end of the 21st Century, all the dunes from South Africa to Zambia and Angola are likely to be reactivated.
Tens or even hundreds of thousands of people would be affected by such changes, the team said.
"The Kalahari is a large area that supports a reasonably big rural population that lives by farming," Professor Thomas explained.
"It's these people who are vulnerable to their currently savannah-like environment becoming a rather more hostile, active, dune landscape than it is today.
He added: "There has been little work done on how the landscape is likely to evolve under climate change impacts.
"We've had a lot of work done on ice-cap melt and glacier retreat; there's been a lot of interest in changes around coastlines, particularly Europe and North America, and the low-lying islands of the Pacific, of course. But relatively little concern has been expressed with regard to the way the landscapes of Africa are likely to change in the 21st Century.
"What we're saying here is that these landscapes are potentially very dynamic and they can kick in with a form of activity that is rather hostile to farming."
The leaders of the major industrial countries, known as the G8, meet in Scotland on 6 July to discuss African development and climate change.
Last week, an alliance of 21 UK-based charities and environment groups issued a report which claimed any G8 strategy to alleviate poverty in Africa was doomed to failure unless urgent action was taken to halt climate change.