Fig. 2 Spatial distribution of the average wind erosion moduli in southern Africa for (a) 1991–2015; (b) 1991–1995; (c) 1996–2000; (d) 2001–2005; (e) 2006–2010; and (f) 2011–2015.

3.2 Temporal-spatial trends for wind erosion

The soil erosion modulus in southern Africa fluctuated from 1991 to 2015, but the temporal changes showed a significant downward trend (Fig. 3a) with an average annual decrease of 0.99 t/ha/a, and a maximum soil loss of 61.01 t/ha in 1995. In general, wind erosion in southern Africa can be divided into three phases. From 1991 to 2000, the amount of wind erosion fluctuated around 46.40 t/ha/a; from 2001–2010, it fell significantly at an average rate of 1.95 t/ha/a; and then it stabilized after 2010. According to Sen’s trend test (Fig. 3b), 70.84% of the southern Africa study area showed a downward trend in annual average soil erosion. This decrease was significant across 66.65% of the area (p < 0.05), but 7.1% of the area showed a significant increase (p < 0.05). The Namib Desert along the western coastal area only had severe soil wind erosion at certain times during the study period (Fig. 2); In the central part of the study area, such as Botswana and Lesotho, the soil wind erosion modulus in local areas showed an increasing trend, but the soil wind erosion modulus showed no significant change over 21.11% of the area.