Soil is a crucial component of the earth system that controls the bio-geo-chemical and hydrological cycles and also offers to many resources, goods and services to the human beings (Berendse et al., 2015). It is the base to support primary production of organic matter and nutrient cycling, control of pests and diseases, decontamination of the environment, and provision of ecosystem services (UNCCD, 2013).
Soil also plays a major role in global climate processes through regulation of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions (FAO and ITPS, 2015). With these and other infinite significances, soil need to be protected in sustainable manner. Global estimates, however, indicate that human pressures on soil resources are reaching critical limits (FAO and ITPS, 2015) and soil is becoming vulnerable to various forms of depletion, such as soil erosion, soil fertility declination, and associated changes in soil physical and chemical properties. Soil erosion is the most severe and widespread incident that occupies 56% (Gelagay and Amare, 2016) or 1094 million hectares of the world’s total land area (Walling and Fang, 2003). In Africa, the problem of soil erosion is estimated to cause damage of $26 billion annually (Lal, 2001).
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Scientists and farmers are becoming increasingly concerned about the declining fertility of soil in the highlands of Eastern Africa and Sub-Saharian Africa (Sanchez and Leakey, 1997). Due to continuous intensive cropping, farmers have experienced declining crop yields over time (Mugendi et al., 1999), raising concerns on the environment and over the land quality by both scientists and farmers. Soil erosion (resulting from cultivation on steeply sloping terrain) and mining of soil nutrients are among the key factors that have led to low agricultural productivity, food insecurity and extensive poverty in Africa (Mugendi et al., 1999). Past soil erosion for the African continent as a whole has caused an average annual crop yield decline of 8.
2% and 6.2% for sub-Saharan Africa (Lal.R, 1995) and that if higher soil erosion rates continue unabated, average annual crops to yield declines in 16.5% and 14.5% for sub-Saharan Africa may be possible.As a result food insecurity is a principal concern and a major challenge to human welfare and economic development in Africa. This indicates that land degradation and soil fertility depletion are considered as the major threats to food security and natural resource conservation in sub- Saharan Africa (Lal, 2001).
In Ethiopia Land degradation is impairing land contribution to food security and to provide other benefits such as fuel wood and fodder. Ethiopians are facing rapid deforestation and degradation of land resources. Population increases have resulted in extensive forest clearing for agricultural use, overgrazing, and exploitation of existing forests for fuel wood, fodder, and construction materials. Forest areas have been reduced from 40 percent a century ago to an estimated less than 3 percent (Badege, 2009). Land degradation problem in Ethiopia is manifested mainly in the form of soil erosion, gully formation, soil fertility loss, and crop yield reduction. The heavy reliance of some 85 percent of Ethiopia’s growing population on an exploitative kind of subsistence agriculture is a major reason behind the current state of land degradation (Gebreyesus and Kirubel, 2009). Similarly, studies conducted by (Temesgen et al.
, 2014a, b) in Dera District, Ethiopia exemplified the increased of land degradation which mainly caused by the growing population of the area. Consequently, poverty and food insecurity are concentrated in rural areas (MoARD, 2010). Similarly, (Shibru ,2010) reported that the loss of soil productivity in Limo Woreda leads to reduced farm income and food insecurity, particularly among the rural poor and thus continuing or worsening poverty.
Land degradation can contribute directly to poverty by reducing the availability of other valuable goods and services important to poor households (for example, fuel wood, construction materials, wild foods, and medicinal plants) and by increasing the demands on labor needed to forage for such goods.