摘要：Soil erosion seriously threatens the future agricultural productivity of Ethiopia's highlands. In analyzing the determinants of soil conservation investments there, this study goes beyond the conventional physical factors to examine institutional, social capital and public program effects. The double hurdle statistical analysis from 250 farms in the Tigray region reveals different causal factors for soil conservation adoption versus intensity of use. The determinants of adoption of soil conservation measures vary sharply between stone terraces and soil bunds. Physical propensity toward erosion (e.g., slope, slope shape and soil texture) and land suitability for conservation helped determine conservation investments in all cases. But institutional and social determinants of investment differed importantly between bunds and terraces. Long-term investments in stone terraces were associated with secure land tenure, labor availability, proximity to the farmstead, and learning opportunities via the availability of food-for-work projects. By contrast, short-term investments in soil bunds were strongly linked to insecure land tenure and the absence of food-for-work projects. Farm beneficiaries of public soil conservation programs were less likely to invest privately in either type of conservation practice. Social capital, as measured by farmer perception of community pressure to curb soil erosion, did not contribute significantly to either kind of conservation investment. The intensity of stone terrace adoption (measured as meters of terrace per hectare) was determined by expected returns but not by capacity to invest. Higher intensity of stone terrace construction was favored by fertile-but-erodible silty soils in (rainy) highland settings that offered valuable yield benefits from soil conservation. Intensity of terracing was also greater in remote villages where limited off-farm employment opportunities made construction costs relatively low. Previous research has highlighted the need for public policy interventions to supplement private incentives to make soil conservation investments in erosion-prone mountain areas. Our results highlight the importance of the right kind of public interventions. Direct public involvement in constructing soil conservation structures on private lands appears to undermine incentives for private conservation investments. When done on public lands, however, public conservation activities may encourage private soil conservation by example. Secure land tenure rights clearly reinforce private incentives to make long-term investments in soil conservation.
