Potentials and Problems in Using Nebkha Dunes as Indicators of Soil Degradation in the Molopo Basin, South Africa and Botswana

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Nebkha dunes, formed from sediment accumulations around shrubs, have been proposed as a reliable, rapid indicator of dryland degradation. This paper aims to investigate the applicability of this link for the Molopo Basin, southern Africa, from sedimentological and biochemical evidence. This study shows that sediments are largely locally derived from interdune areas suggesting saltation and surface creep are the key aeolian transport processes leading to nebkha formation. The local derivation of sediments implies that windblown losses from neighbouring agricultural fields and regional scale movements of suspended dust are minimal and not required for nebkha development. Nebkha sediments are significantly enriched in available inorganic nutrients (N and P), suggesting that sediment movements, litter inputs and/or improved conditions for nutrient mineralisation can lead to an increase in spatial variability of soil chemical characteristics. However, nutrient-enriched sub-canopy niches on nebkhas retain a seed resource of palatable grass species even in intensively grazed areas. Further, the use of nebkha resources by local communities suggests that although nebkhas do indicate aeolian transport of sediment, the immediate association with soil degradation is questioned and thus requires further investigation in southern Africa.KeywordsLand DegradationWind ErosionArid EnvironmentSoil DegradationUnited Nations Environment ProgrammeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.