African Water Development Report 2006 - United Nations Economic ...

African Water Development Report 2006tivation methods. A chain action and reaction isgoing on with the productive capacity of the landfalling because of shorter fallow rotations, lowerratic rainfall, soil erosion, reduction of soil fertilityby soil mining, declining soil organic mattercontent and overgrazing. It is estimated thatAfrica accounts for 27.4 per cent of the world’sland degradation and that 500 million ha of landin Africa are moderately to severely degraded(UNEP, 2001).The most serious effect of land degradation issoil degradation and it is estimated that 14 percent of degraded soil results from vegetation removal,13 per cent from overexploitation, 49.5per cent from overgrazing and 24 per cent fromagricultural activities (WRI, 1992). Soil lossesare reportedly considerable in North Africa andEast Africa. In Ethiopia and Uganda, soil erosionaccounts for over 80 per cent of the cost ofenvironmental degradation, estimated at about1-4 per cent of GDP. Ethiopia is reportedly losing1.9 billion tons of topsoil from the highlandsannually, while Burundi is losing 80 to 150 tons/ha/year and Rwanda about 557 tons/ha/year(CT&E, 2000; CEDARE, 2000). In South Africa,soil losses are estimated to be as high as 400million tons annually and in Malawi, soil lossesrange from 0 to 50 tons/ha/per/year (UNEPGEO-2000).The water-retention capacity of soil is highlybeneficial to agriculture. This capacity, which isalso beneficial to groundwater levels that it helpsto replenish, is removed by increased deforestation,mainly from harvesting of fuelwood, resultingin the lowering of groundwater levels in aridareas. Similarly, poor management of drylands inAfrica, particularly in areas with high populationgrowth rates, heightens the rate of desertificationin these areas as more and more people andlivestock encroach on the land. It is estimatedthat 72 per cent of the arable land and 31 percent of the pastoral land in Africa are degraded(ECA, 2001).Moreover, over-abstraction and/or over-regulationof the flow of surface waters affects thein-stream environment and downstream consumptiveuses, exacerbates saltwater intrusion,affects the productivity of land in estuarine areas,and reduces the water’s capacity for dilutingwaste discharges. Irrigation development,which is accompanied by the construction ofnumerous canals, is one way in which water isFig. 6.1: Evolution of per capita Irrigated areas in Morocco3530252015196819721976198019841988199219962000ha/1000hab126