Global Warming Forecast to Set Kalahari Dunes Wandering

OXFORD, UK, June 30, 2005 (ENS) - The vast dunefields of southern Africa's Kalahari Desert, which have been still for 16,000 years, could be shifted by global warming, researchers from Oxford University predict.

The study, reported today in the journal "Nature," warns that large areas of land that now produce food and forage could become engulfed by dunes that will begin to wander as Earth's surface temperature heats up.

These shifting sands are likely to destroy local ecosystems, making any kind of farming or other use of nearby land even more difficult, they report. The study predicts that the social consequences to the region's most vulnerable people will be "drastic."

These dunes spread across 2.5 million square kilometers from the northern end of South Africa, through Angola, Botswana and Namibia, to western Zimbabwe and western Zambia.

The team, led by Professor David Thomas, a geographer, urges politicians in the region to avoid development that might make this problem worse. "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," Thomas told BBC News.

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Kgalagadi Transfrontier Park takes in parts of the Kalahari in South Africa and Botswana. (Photo courtesy SANParks)
Using data collected from 1960 to 1991, Thomas and his colleagues took data from three different computer models that are used to forecast climate change to 2100.

The scientists put the data into a specialized climate model specific to the Kalahari dunefields. They calculated the effects of vegetation loss, lower moisture content, and increased wind energy on African desert regions.

Their simulations revealed an increase in dune activity in the southern dunefields of Botswana and Namibia by 2040, while the more northerly and easterly dunes in Angola, Zimbabwe and Zambia begin to move by 2070.

By the end of the 21st century, all the dunes from South Africa to Zambia and Angola are likely to be reactivated, they predict.

The Oxford model included seasonal variations in annual rainfall and the likely impact of an increase in atmospheric greenhouse gases on temperature. But it did not include the influence of higher carbon dioxide levels on plant productivity, nor human impacts such as increased agriculture in surrounding areas.

Local people are aware of the problem, says Thomas, but often act to worsen it. Large flocks of sheep in the northern part of South Africa, for instance, reduce available ground water, because their care requires extensive well digging.

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Black-maned lions are the top predators of the Kalahari. Wildlife is also at risk as global warming shifts the Kalahari dunescape. (Photo courtesy SANParks)
Dune movement can be slowed or prevented by sparse vegetation. But when vegetation cover drops below 14 percent, erosion speeds up. The result is a self-perpetuating system in which the blown sand smothers remaining plants, destroying ecosystems and prompting further erosion, Thomas explains.

"Fighting the process of vegetation loss and dune movement would require major adaptations," says Thomas.

One possible solution would be to plant new vegetation. But dune ecosystems are very sensitive and differ greatly from region to region. He says, "It would take many years of careful tending to stop a moving dune from wandering around."

The Group of Eight leaders of the world's wealthiest countries, the G8, meet in Scotland July 4 to 6. Host British Prime Minister Tony Blair has placed African development and climate change at the top of the agenda.

Last week, an alliance of 21 UK nongovernmental organizations and environment groups issued a statement warning that any G8 strategy to alleviate poverty in Africa was doomed to failure unless urgent action is taken to limit climate change.

The Kyoto Protocol, which requires industrialized countries to reduce their greenhouse gas emissions to an average of 5.2 percent by 2012, has been ratified by all G8 governments with the exception of the United States. Still, it is viewed as a small first step towards controlling global warming.