Abstract:
Land degradation is a global, ongoing and relentless problem diminishing the functions and services provided by land resources. The problem is most serious in tropical regions, high in population density and mainly dependent on subsistence agriculture. Ethiopia can be viewed as a vivid example of countries in these regions most affected by land degradation. Although its extent varies, the problem is widespread in all regions of the country. The highlands, originally endowed with abundant natural resources have been turned into cultivated fields leading to widespread environmental damages. Although deep formation and productive soils in most areas of the central highlands has overshadowed the adverse effects of land degradation until recently; the crises commenced with imperceptible losses of natural resources has reached the level of visible impacts on land productivity and the environment. This study dealt with a range of factors (social, economic and biophysical) related to land degradation in Dendi-Jeldu districts of Oromia, central Ethiopian highlands. To this end, a series of experiments were carried out at different scales (plot, farm, watershed, and districts). Variables examined included the dynamics of land use and land cover (LULC)changes in the period 1957-2014; drivers and impacts of LULC; socio-economic conditions, infrastructure and institutional development; land evaluation; farming practices and their interplays with land degradation, and the perceptions of farmers’ on various aspects of land degradation. Over the last half century (1957-2014), LULC pattern have changed considerably with the expansion of cultivated land (CL) into pastureland (PSL) and forestland (FL). Pastureland, FL and woodland (WL) that were 49,21 and 5 percent, respectively in 1957have shown substantial decline by 67, 73 and 100 percent, respectively in 2014. Progressive and indiscriminate expansion of CL reached the maximum limit in the mid 1990s. Expansion of plantations (Eucalyptus globulus) was also remarkable. Plantation areas of 0.1% in 1957 had grown to 8% of the total land area in 2014 with an increase by 13,785 percent. Pastureland has been the principal source of land for CL expansion and conversion was serious in the period between 1980 and 1995. Deforestation and use of land for cropping, pasture and plantation has also been remarkable in the periods 1957-1980 and 1995-2014. Pastureland in the earlier period (1957-1995) and CL in the later period (1995-2014) were the major sources of land for plantations. The observed land use changes, particularly CL expansion, have been linked to ever rapid growth of the population (Inhabitants of41km-2 in 1957 has grown to 180 km-2in 2014). Moreover, changing land tenure system biophysical and economic factors have also partly contributed to the LULC dynamics.Net increase in livestock numbers set against a reduction in PSL was a paradox. These together shift the balance of ecosystem leading to land degradation. Changes in soil physical property (bulk density), declining soil fertility and poor land cover were linked to soil hydraulic properties (runoff) that led to severe soil erosion in the area. It was particularly serious on CL (27-49 t ha-1 yr-1) and fallow land (11-37 t ha-1yr-1). Erosion rates greatly varied with the LULC type, land management and the topographic conditions. Rates of soil erosion from PSL (7-17 t ha-1 yr-1) were also above tolerance limits. Plantations, however, proved to significantly reduce soil erosion (3 t ha-1yr-1).In most cases, soil erosion studies were linked to CL. However, with diminishing grazing areas, many attributes of livestock management systems is also actively contributing to land degradation. In the highlands, land (a scarce resource) is often used for purposes it is not most suited due to constraints from climatic and land characteristics contributing to low productivity. In the study area, soil acidity, low temperature and topography were the most apparent limitations for the existing agricultural land uses. If agriculture is practiced, systematic and categorized use of land based on its potentials is essential. Hence, the current land use system generally requires urgent structural adjustment for sustainable use of land resources. Moreover, land shortages, low educational levels, low infrastructure development, limitations in institutional services and low economic endowment in rural Ethiopia also contributed to the exploitive agriculture leading to land degradation. Hence, sound interventions need proper sequencing across these domains to solve critical societal problems. Moreover, community perceptions on processes and impacts of land degradation could not step beyond positive outlook and needs further participatory efforts. The problem of land degradation is widespread and driven by several factors across various sectors. Therefore, sustainable land management and development require rational and multi-sector decisions that lead to a common goal fostering conservation and optimal use of resources.