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Remobilization of southern African desert dune systems by twenty-first century global warming

Abstract

Although desert dunes cover 5 per cent of the global land surface and 30 per cent of Africa, the potential impacts of twenty-first century global warming on desert dune systems are not well understood1. The inactive Sahel and southern African dune systems, which developed in multiple arid phases since the last interglacial period2, are used today by pastoral and agricultural systems3,4 that could be disrupted if climate change alters twenty-first century dune dynamics. Empirical data and model simulations have established that the interplay between dune surface erodibility (determined by vegetation cover and moisture availability) and atmospheric erosivity (determined by wind energy) is critical for dunefield dynamics5. This relationship between erodibility and erosivity is susceptible to climate-change impacts. Here we use simulations with three global climate models and a range of emission scenarios to assess the potential future activity of three Kalahari dunefields. We determine monthly values of dune activity by modifying and improving an established dune mobility index6 so that it can account for global climate model data outputs. We find that, regardless of the emission scenario used, significantly enhanced dune activity is simulated in the southern dunefield by 2039, and in the eastern and northern dunefields by 2069. By 2099 all dunefields are highly dynamic, from northern South Africa to Angola and Zambia. Our results suggest that dunefields are likely to be reactivated (the sand will become significantly exposed and move) as a consequence of twenty-first century climate warming.

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Figure 1: The southern African Kalahari basin and dune systems.
Figure 2: A p, GCM dune mobility predictions using IS92a (2 × CO 2 ) emissions scenarios.
Figure 3: Contemporary and post 2070 A p, GCM values of Kalahari dunefield activity.
Figure 4: Predicted three-month block dunefield activity after 2070.

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Acknowledgements

We thank P. Coles for draughting figures, and the University of Sheffield for financial support to M.K. H. Viles supplied Namib weather data used in model validation.

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Correspondence to David S. G. Thomas.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Figure S1

This illustrates the classification of PAGCM into four classes, and exemplifies the data sources used to achieve this calibration of the index. (PDF 100 kb)

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Thomas, D., Knight, M. & Wiggs, G. Remobilization of southern African desert dune systems by twenty-first century global warming. Nature 435, 1218–1221 (2005). https://doi.org/10.1038/nature03717

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