Analysing the social benefits of soil conservation measures using stated preference methods

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.