The researchers used different climate models and different emission scenarios to predict what effect global warming will have on the desert dunes.
"We found that as the century progressed, the dune fields of the mega-Kalahari reactivate, partly due to erodibility increasing as precipitation declines, and partly as wind energy increases, especially toward the end of the dry season when surfaces are least vegetated," Thomas said.
The study showed that the southern dune fields of Botswana and Namibia, which are the driest, will become activated by 2040. The more northerly and easterly dunes in Angola, Zimbabwe, and Zambia will begin to shift by 2070.
By the end of the 21st century, all the dunes in the Kalahari region are likely to be on the move.
"These are areas where dunes are currently wooded in many places," Thomas said. "We'll potentially see major environmental changes [with] currently vegetated but sandy landscapes reverting to active, blowing sand seas where life will potentially be very difficult."
Such widespread, desert-like conditions with active sand dunes throughout the Kalahari area have not occurred in more than 14,000 years.
The sand would not necessarily blow all year round, but mainly in the windy months. This is the case in the hyperarid dune fields that are found today in parts of Saudi Arabia and the Namib Desert in southern Africa.
"Often it is the high points of the dunes, the crests, that blow first as the wind strengths tend to be higher there," Thomas said. "But as lower dune slopes lose vegetation, they become susceptible to transport, too."
The dune field areas in the Kalahari often support livestock farming, which will become much more difficult if these presently quiet dune fields revert to activity, experts say.
"This is a very important [study] that shows how currently semi-arid area may respond to global warming," said Nicholas Lancaster, a research professor at the Division of Earth and Ecosystem Sciences at the Desert Research Institute, based in Reno, Nevada.
"The implications for southern Africa are hugeespecially for cattle herders, wildlife, and tourism," Lancaster added.
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