Impact on erosive runoff and costs for local communities of agricultural-soil-use-change scenarios: the case of Pays de Caux (France)

Recurring mudflows in the silty areas of North-West Europe and particularly in Pays de Caux (France) result in significant costs for local communities. These flows result from erosion processes which occur on agricultural land located upstream of urban areas. Farming practices depend on changes in external factors (prices, regulatory system) that may lead to an increase in erosion and mudflows issues. Public-action programs can limit the possible damage of these changes but any strengthening of these policies (compensation for farmers) induces costs for the community. Our goal is to examine the economic feasibility of action programs designed to counter some agricultural scenarios driven by changing external factors. To do so, we compared the cost of compensating farmers with the local populations’ willingness to pay (WTP). We built scenarios of changes in farming systems with a 2015 horizon at the scale of the Pays de Caux, 2007 being the initial situation. We chose two scenarios of the disappearance of dairy farming, since local stakeholders were concerned with the future of local livestock farming and particularly by trends of declining dairy farming. One scenario (StopMilk) did not include any public-action program, the other one (StopMilkEnv) involved a program based on the funding of environmental-friendly cultivation techniques . These scenarios were assessed at the small watershed scale (7 km²) in terms of both changes in farming systems and effects on runoff. Finally, the economic evaluation of additional costs of StopMilkEnv was extrapolated at the level of the Austreberthe watershed syndicate1 (214 km²). Our results show that StopMilk leads to a significant increase in runoff, whereas the local public-action program proposed with StopMilkEnv reduces runoff below the 2007 level. The willingness to pay of the residents of the Austreberthe watershed for a 5 years program was around €395,000/year and a comparison with the cost of the environmental-friendly cultivation techniques revealed that the funding of such practices would be possible but would require borrowing by the community.