Résumé
In the economic literature on the motivations underlying voluntary contributions to environmental public goods, little attention is granted to the way the overall objective of the environmental program is framed. A program which contributes to an increase of environmental quality can be perceived differently from a program designed to bring back the environmental quality to its original level, after it was damaged by human intervention, even if net environmental gain is equivalent in both programs. How does it impact participation rates and contribution levels? This paper addresses this issue in the context of agri-environmental contracts for biodiversity conservation. It compares farmers' willingness to participate in two equivalent agri-environmental schemes, one being framed as part of a biodiversity offset program, the other one as a biodiversity conservation program. We demonstrate with a discrete choice experiment that biodiversity –offsets programs must offer a greater payment to enroll farmers compared to the latter. This is explained by the sensitivity of farmers to environmental issues.