Fig. 4 Relationships
between wind erosion, and temperature and precipitation in southern
Africa due to temporal changes in the (a) mean annual temperature and
(b) annual precipitation. Spatial distributions of (c) mean annual
temperature and (d) annual precipitation. Spatial patterns of the
partial correlations between wind erosion, and (e) mean annual
temperature and (f) annual precipitation.
The annual maximum wind speed in southern Africa showed a clear downward
trend from 1991 to 2015, with a decline rate of 0.0742 m/s/a (r² = 0.87,
p < 0.01) (Fig. 5a). A significant drop in the wind speed led
to a reduction in soil wind erosion (Fig. 3a). There was a significant
positive correlation (p < 0.1) between the annual wind erosion
modulus and the annual average maximum wind speed across 68.18% of
southern Africa (Fig. 5b), mainly distributed in the Kalahari Basin of
South Africa and southern Botswana. A slight rise in wind speed in
2003–2004 and 2006–2007 led to an increase in the average annual wind
erosion modulus, which suggested that wind speed had a strong influence
on wind erosion spatial distribution and temporal changes. However,
near-surface wind speed is not the main factor affecting soil erosion in
the Western Coastal Namib area where the soil erosion is more likely to
be affected by the surface rock structure and lower vegetation coverage.