Fig. 1 Geographical location of the study area, including political borders and main topographic features.
The temperature, precipitation, wind speed, and other meteorological data used in this study were all derived from the Global Surface of Daily Meteorological Data produced by the National Centers for Environmental Information (NOAA, https://www.ncdc.noaa.gov/). More than 200 meteorological stations in southern Africa and its surrounding areas were selected. The data covered 1991–2015 and ANUSPLIN 4.3 (https://fennerschool.anu.edu.au/research/products/anusplin) was used to spatially interpolate the information. The Digital Elevation Model (DEM) was provided by the Shuttle Radar Topography Mission and has a resolution of 90 m (http://srtm.csi.cgiar.org/srtmdata/); the soil properties were determined using 250 m resolution raster data from the International Soil Reference and Information Center and included sand, clay, silt, and organic matter contents (https://soilgrids.org/); the CaCO3 data came from the Harmonized World Soil Database (HWSD v1.2) with a resolution of 1 km (http://www.fao.org/soils-portal/soil-survey/); the vegetation data were obtained from the standard normalized vegetation index (NDVI) in GIMMS 3g and covered 1991–2015 with a spatial resolution of 8 km; and the vegetation coverage was calculated by the maximum synthesis method (https://ecocast.arc.nasa.gov/data/pub/gimms/). The land use/cover data came from the European Space Agency and its Climate Change Initiative (CCI-LC) project provided global land use data with a resolution of 300 m (http://maps.elie.ucl.ac.be/CCI/viewer/). All data were uniformly resampled to a spatial resolution of 8 km.

2.2 Revised wind erosion equation

The RWEQ model is an empirically-based model developed by the United States Department of Agriculture to estimate soil loss in farmland at a height of 2 m (Fryrear et al., 2000). When the wind force is greater than the resistance, the soil particles will move, and when the wind force is less than the resistance, the soil will not be eroded by wind. The RWEQ model is based on the WEQ and includes its experience and process components. It can predict and simulate wind erosion processes by combining existing data sets and computer models (Jarrah, Mayel, Tatarko, Funk, & Kuka, 2020). Compared to other complexity models that have more parameters, the RWEQ model has a relatively simple structure and has been widely used to estimate the transport capacity of long-term and large-scale aeolian sediments (Borrelli et al., 2017; Guo et al., 2013; Youssef et al., 2012; Zobeck et al., 2000). The model calculation is as follows: