ANALYSIS Analysing the social benefits of soil conservation measures using stated preference methods Sergio Colombo a, * , Javier Calatrava-Requena a , Nick Hanley b a Department of Agricultural Economics, Instituto Andaluz de Investigacio ´n Agraria (IFAPA), Andalucı ´a Government, Camino de Purchil s/n, 18004 Granada, Spain b Department of Economics, University of Stirling, Stirling FK94LA, Scotland, UK Received 29 March 2005; received in revised form 13 September 2005; accepted 18 September 2005 Available online 2 November 2005 Abstract The paper estimates the benefits of programmes to mitigate the off-site impacts of soil erosion for a watershed in Andalusia, Spain. Two stated preference methods are used, namely choice experiments and contingent valuation, to obtain estimates of the social benefit from soil erosion reductions under two different methodologies. We emphasise the relative merits of the choice experiment method to provide useful inputs to policy design. However, employing both methods allows us to undertake a convergent validity test and thus to provide more defensible social benefit estimates. The attributes used in the choice experiment include water quality impacts (which we find to have the highest marginal values), impacts on wildlife and the area subject to a control programme. The contingent valuation design includes an attempt to reduce bias by reminding respondents about substitutes. Results are used to suggest upper limits on per hectare payments for soil conservation programmes. D 2005 Elsevier B.V. All rights reserved. Keywords: Convergent validity test; Choice experiments; Contingent valuation; Soil erosion 1. Introduction Soil is a non-renewable resource which is indis- pensable for life. In the south of Spain, soil erosion rates are extremely high due to climatic conditions, soil characteristics and the nature of tillage systems employed in many olive groves, a cultivation style that cause severe land degradation yet which occupies most of the cultivated area of the eastern part of Andalusia region (MAPA, 2000). One reason for high soil erosion rates is the fact that all olive groves are privately owned, and farmers are not rewarded by the market for reducing soil erosion rates to the level which society demands. This is for several reasons. First, since the effects of soil erosion occur with a time lag, farmers may not perceive these effects, or may 0921-8009/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolecon.2005.09.010 * Corresponding author. E-mail address: scolombo@ugr.es (S. Colombo). Ecological Economics 58 (2006) 850 – 861 www.elsevier.com/locate/ecolecon