1.

Soil Degradation

South Africa’s soils are generally fragile, climatologically and topographically predisposed to land degradation through soil erosion, which is a natural process up to the point where it is accelerated due to human activities such as deforestation, overgrazing, forest fires and construction activities (DEA, 2012).

2.

Vegetation Degradation

High rates of vegetation degradation have been observed in Limpopo, KwaZulu-Natal and communal areas of the Eastern Cape (DEA, 2008). These areas have high proportions of grazing lands and experience problems of decreased vegetative cover, bush encroachment, alien plant invasions and changes in species composition. Bush encroachment is also severe in the dry areas of the Northern Cape, the western parts of the North West and the south-western Free State (DEA, 2008).

3.

Water Erosion

Erosion is a major problem in South Africa (Pretorius, 1998; Le Roux et al., 2007), and rainfall and subsequent runoff are the major sources of erosive and transport energy. Erosion by water can be categorised as sheet, rill and gully erosion (Morgan, 2005; Le Roux et al., 2008).

It is not possible to draw a clear distinction between these forms of erosion, but they do vary in, as far as their simultaneous occurrence during varying watershed stages. According to Al-Kaisi (2008), while erosion reduces the productivity of land, it also contributes to water quality deterioration. In South Africa, soil water erosion is the major carrier of nutrients and pollutants to water bodies.

4.

Wind Erosion

Wind erosion is a crucial issue in arid and semi-arid regions (FAO, 1960; Wolfe & Nickling, 1993; Borrelli et al., 2014). Nearly 28% of the global land area is affected by this phenomenon (Oldeman, 1994; Callot et al., 2000; Prospero et al., 2002; Webb et al., 2006; Du et al., 2015). This type of erosion decreases soil productivity and has a negative effect on the environment because eroded fine particulates become suspended in the atmosphere (Sterk & Raats, 1996; Sharratt et al., 2007; Visser & Sterk, 2007; Borrelli et al., 2014). In South Africa, soil wind erosion is closely related to the natural and human-induced removal of vegetation cover (Wiggs et al., 1994). According to Pretorius (1998), 25% of South Africa is susceptible to wind erosion. This percentage is likely to grow due to the loss of vegetation in rangelands and tillage practices in agricultural lands. Several studies undertaken have delineated large areas of the Northern Cape, the western part of the North West Province and the northwest part of the Free State Province as significant sources of dust emission in South Africa (Ginoux et al., 2012). Furthermore, major natural dust emission source areas occur in the arid and semi-arid parts of South Africa such as Namaqualand, Swartland and ephemeral lakes (Ginoux et al., 2012).

5.

Alien Plant Invasion

South Africa is among the countries that have a long colonial history of invasive alien species. Several thousand species of alien plants have been introduced into South Africa. Many of these have become naturalised and some, following a long ‘lag’ phase which may last many decades, suddenly increased in abundance and became invasive weeds. The introduction of invasive species in South Africa dates back to the 1600s and peaked in the 1800s, which resulted in over 500 species being listed as damaging in agricultural and natural ecosystems. Several invasive species are also responsible for decreasing water run-off and groundwater reserves at rates that are far in excess of water usage by the natural vegetation types, which is especially problematic in this water-scarce country.