Assessing the costs and benefits of improved land management practices in three watershed areas in Ethiopia

摘要

Highlights ? We examine the on-site costs and benefits of three major soil conservation measures. ? A production function is estimated as the basis for the cost–benefit analysis. ? We show that soil conservation measures significantly increase productivity. ? A longer term perspective is needed for these private welfare gains to materialize. Abstract Unsustainable land use management and the resulting soil erosion are among the most pervasive problems in rural Ethiopia, where most of the country’s people live, jeopardizing food security. Despite various efforts to introduce soil conservation measures and assess their costs and benefits, it is unclear how efficient these measures are from an economic point of view in securing food production. This paper examines the costs and benefits of three soil conservation measures applied in the country in three different rural districts facing different degrees of soil erosion problems using survey data collected from 750 farm households. A production function is estimated to quantify the costs and benefits of more sustainable land use management practices. We show that the soil conservation measures significantly increase productivity and hence food security. Comparing the costs and benefits, the results indicate that implementing soil conservation measures would benefit farm communities in the case study areas through increased grain productivity and food security. Keywords Soil conservation ; Cost–benefit analysis ; Cobb–Douglas production function ; Blue Nile ; Ethiopia prs.rt("abs_end"); 1. Introduction Soil erosion and the resulting agricultural land degradation are the most severe environmental problem in the Ethiopian highlands ( Shiferaw & Holden (1999) , Pender, Gebremehedhin, Benin, & Ehui (2001) , Amsalu & de Graaff (2007) and Tefera & Sterk (2010) Pender, Gebremehedhin, Benin, & Ehui, 2001 ; Shiferaw & Holden, 1999 ; Tefera & Sterk, 2010 ), jeopardizing the sustainability of agricultural production and ultimately national food security ( Sonneveld & Keyzer (2002) and Kassie et al. (2008) ). The on-site effects are a major source of concern since they threaten the livelihoods of a majority of the country's population. The highlands of Ethiopia cover 40 percent of the country’s land mass and are home to almost 88 percent of its human population and 70 percent of the total livestock population ( Ayele, 1999 ). The causes underlying land degradation are a combination of climate conditions and extreme weather events, such as heavy rainfall and droughts, population pressure, unsustainable agricultural land use practices such as overgrazing, cultivation of steep slopes, and no or limited fallow periods ( Geist & Lambin, 2004 ), and lack of institutions to enact regulations or laws that enhance sustainable land management practices ( FAO, 2011 ). The problem is transboundary in nature particularly in the upper Blue Nile basin where soil and excessive runoff that leave the boundary of individual farms cause off-site or off-farm impacts to reservoirs, irrigation schemes and waterways downstream across political borders. An example is the sedimentation of the Gezira irrigation scheme in Sudan due to massive erosion from the Upper Blue Nile river basin. Ahmed (2003) reported that the sediment load of the Blue Nile at the border at El Diem (120?km upstream of the El-Roseires Dam) is 140 million tons per year, causing management difficulties of irrigation canal networks in the Gezira scheme and consuming more than 60 percent of the total costs of the operation and maintenance in sediment clearance. In the Ethiopian highlands, topsoil loss due to soil erosion is estimated to be 1.5 billion tons per year ( Taddese, 2001 ), and average annual soil loss from cultivated land is 42?t/ha ( Hurni, 1993 ). This is very high compared to other countries worldwide ( Pimentel, 2006 ). Total estimated soil erosion in the US, for example, a country 9 times the size of Ethiopia is 3 billion t/year (Carnell, 2001 cited in Pimentel, 2006 ). The estimated soil formation rate in Ethiopia is less than 2?t/ha/year, which is very low compared to the estimated soil erosion rates ( Hurni, 1983 ). Worldwide soil erosion rates are highest in Asia, Africa and South America, averaging 30–40?t/ha/year, and lowest in the United States and Europe, averaging about 17?t/ha/year ( Barrow, 1991 ). Studies conducted in the Amhara region confirm that soil loss due to erosion has a significant impact on the decline of crop yield and loss of agricultural land (e.g. Ludi, 2002; Shiferaw & Holden, 1999 ; Sonneveld, 2002 ). In order to mitigate the problem of soil erosion, the regional government and non-governmental organizations have supported various efforts to introduce soil conservation measures.