Chapter 2: State and Trends
health impacts such as the spread of disease, including HIV/ AIDS. Between 1960 and 1980, almost 10 million people in the sub-Sahara African region had to move because of drought (El Hinnawi 1985; Jacobson 1989). Studies from a number of African countries, including Burkina Faso, Egypt, Mali, Morocco and Niger, indicate that land degradation and desertification contribute to human mobility, and to worsening living conditions for both those who leave and those who remain (UNCCD 2014).
Soil salinization Inefficient irrigation practices and poor management of fertilizers lead to loss of top soil and salinization, resulting in loss of soil fertility and poor plant growth. Soil salinization is also caused by scarcity, variability and unreliability of rainfall and the high potential for evapotranspiration that affects the water and salt balance of the soil. With the projected increase in dry conditions in some parts of Africa as a result of climate change, this phenomenon is likely to rise.
The areas most affected by salinization are the arid and semi-arid regions of North and Southern Africa where about 30 per cent of irrigated land has been lost due to salinization, with examples from Kenya, Nigeria, Sudan and Tanzania showing losses of irrigable land of 30, 34, 27 per cent and 27, respectively (FAO 2011). In Southern Africa salinization is particularly serious in Botswana and Namibia (Sommer et al. 2013).
Soil erosion Cultivation in much of Africa encroaches on environmentally fragile areas such as steep slopes, riverbanks, shallow soils and wetlands, often without appropriate conservation measures in place, leading to increased soil erosion. Due to small landholdings, farmers are forced to use their land continuously with no rotation, resulting in declining crop yields and the loosening and washing away of soil exposed to natural forces such as wind and water.
The offsite impacts of soil erosion include sedimentation of water bodies and loss of breeding grounds for fish, and destruction of infrastructure such as roads and bridges, among others. In the Shire River catchment area of Malawi, soil erosion is estimated at more than 25 tonnes per hectare per year (World Bank 2012), and this has the potential to disrupt hydropower generation on the Shire River.
Increased deforestation exposes soil to wind and water erosion. The forest stabilizes the soil and allows water and soil nutrient cycling, and its absence affects the productivity of land as well as human health. In most parts of Africa, deforestation rates exceed planting rates by a factor of 30 to 1 (FAO 2011). In Tanzania, Zambia and Zimbabwe, forest losses to deforestation during the period 2000 and 2005 ranged from 313 000 to 445 000 hectares per year, representing annual rates of 1.1, 1.0 and 1.7 per cent, respectively (Syampungani et al. 2012). In the Congo Basin, deforestation between 1990–2000 and 2005–2010 was variable, with a decreasing trend in Gabon due to much improved forest management practices, but a rising trend in the other Congo River Basin countries.
Desertification Land degradation in drylands can result in desertification. The desert lands of the Sahara, Namib and Kalahari, as well as the drylands of northern Kenya, southern Ethiopia and most of Somalia, cover around 40 per cent of the land surface of Africa (European Union 2013). Coupled with climate change, increasing numbers of cattle and other livestock accelerate desertification. In some parts of Africa, such as in Botswana and Namibia, there has been an on-going trend in livestock numbers exceeding the carrying capacity of the land. For example, the cattle population in Botswana rose from just over 2.1 million in 2005 to nearly 2.6 million in 2011, exceeding the carrying capacity by not less than 40 per cent of the nation’s pasture (SADC 2014). In East Africa, numbers of cattle in Ethiopia increased from 40.4 million in 2005 to 52.1 million in 2011, while in Kenya numbers increased from 13.0 million to 18.2 million over the same period (FAO 2015).
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