The Impacts of Land Use Land Cover Dynamics on Soil Degradation and its Interlocking Conservation Measures in Zoa Watershed of Omo-Gibe Basin, Southwest Ethiopia

Abstract

Background of the Study Soils have played significant roles in the earth’s life-support system through the provision of a multitude of essential ecosystem services such as provisioning, regulating, supporting services and ecological functions to humans (Baveye et al., 2016; Schwilch et al., 2016; Nigussie et al., 2017; González-Morales et al., 2018). However, the adverse effect of soil degradation mainly as soil erosion has been considered as continuous environmental problem and the most serious issues resulting in on-site nutrient and productivity decline, and offsite sedimentation yields in hydraulic structures in world-wide (Pimentel and Burgess, 2013; Amsalu and Mengaw, 2014; Tesfaye et al., 2018; Girma & Gebre, 2020; Dinka, 2020). Globally, soil erosion accounts for 70–90% of total soil degradation, of this around 66% are found in Asia and Africa (Tesfahunegn et al., 2012). Accordingly, the average rate of soil loss by erosion in the world is estimated to be 12 to 15 t/ha/year implying a loss of 0.90–0.95mm topsoil every year (FAO, 2015). Land use land cover dynamics and soil degradation are highly interrelated (Messay, 2011) because usually the changes are associated with deforestation, biodiversity decline and soil loss (Tsegaye, 2019). In addition, natural and anthropogenic-induced land use land cover (LULC) dynamics have significant impacts on soil degradation mainly deteriorating the physical (soil loss by erosion) and chemical properties (soil acidification, nutrient leaching and organic matter depletion) as well as the biological activity of the soil (Sharma et al., 2011; Sebhatleab, 2014; Minta et al., 2018). Land use land cover dynamics have been accounted for an overall increase of 2.5% in the global average soil loss (Woldemariam & Harka, 2020), and about 80% of the world’s farmland use suffers from moderate to severe erosion (Bekele & Gemi, 2020). Similarly, the portion of land use with highly degraded soils had increased from 15% of the total land area in 1991 to 25% by 2011; most of this degradation is associated with water-induced soil erosion, and 10 million hectares of croplands have been lost every year due to soil erosion (UNCCD, 2013). In order to curb the impacts of soil degradation, the government of Ethiopia launched large-scale conservation schemes in the 1970s primarily after the famines with purposes of improving crop productivity and livelihood of the rural farmers (Hawando, 1997; Adimassu et al., 2014; Haregeweyn et al., 2015; Engdayehu et al., 2016; Sinore et al., 2018; Sultan et al., 2018; Sileshi et al., 2019). Consequently, large areas have been covered with structural SWC measures and millions of trees have been planted (Tesema et al., 2020). Among physical measures, the traditional terraces in Konso (Beshah, 2003) and the development of terraces under traditional agriculture in the Tigray highlands and in the Chercher Highlands (Virgo & Munro, 1977), however, these control measures could not bring to halt soil degradation due to continued population pressure and multiple land use types, it is more likely to be even more severe in the future (Legese & Gelanew, 2018). The reasons for failures include poor watershed management approaches that especially focused on physical soil and water conservation practices, but not 2 based on scientific reasoning like constructing structure without determining the amount of runoff expected (Adimassu et al., 2014; Bekele & Gemi, 2020; Tesema et al., 2020). Besides, the farmers were totally ignored from decision-making during the selection, planning and implementation processes of SWC measures and the activities were carried out without attention. Consequently, these efforts have generally failed mainly due to a lack of support and awareness among farmers and identify determinant factors (Haregeweyn et al., 2015; Sileshi et al., 2019). Wordofa et al. (2020) also reported that the effectiveness of the government’s efforts to promote improved structural SWC measures has not been adequately studied across the various agro ecological zones of the country. Therefore, effective soil and water conservation practices for sound landscapes can be realized only when farmers understand soil degradation problems and each land use types, then accept and decide on the purposes of each SWC measures by agroecologies and actively involved in the implementation and maintenance processes with identifying important determinants (Moges &Taye, 2017). Therefore, this study is to assess the impacts of land use land cover dynamics on soil degradation and its interlocking conservation measures in Zoa watershed of Omo-Gibe Basin, Southwest Ethiopia.