Dunes shift when winds pick up sand grains and deposit them some distance away. How much movement occurs depends on a number of factors including wind strength, the amount of vegetation cover and moisture levels. David Thomas of the University of Oxford and his colleagues investigated what might happen to the immense dune fields in southern Africa over the coming years using three global climate models. They first calibrated the models using data collected between 1961 and 1990 and found it agreed well with observed dune activity. All three models predicted that the erodibility of the dunes was likely to increase. By 2040, sands in Botswana and Namibia could start to move, the team reports, with dunes in Angola, Zimbabwe and Zambia beginning to shift by 2070.
The last time the dune fields moved this much was more than 14,000 years ago, the scientists report in the current issue of the journal Nature. And because people in the region depend heavily on farming and agriculture, they note, the changes to the landscape could have severe reverberations.