Combining narrative scenarios, local knowledge and land-use change modelling for integrating soil erosion in a global perspective

Mediterranean soil resources are heavily affected by water erosion. There is a need for anticipating the potential impact of land-use change at the catchment scale, considering a range of contrasted possible changes, in order to prepare a relevant adaptation strategy. While participatory scenario approaches are useful for unveiling the diversity of possible futures, their outputs generally take the form of narratives that may be difficult to relate to biophysical models used for simulating soil and water processes. We addressed this challenge by developing a methodology combining narrative scenarios and land-use change modelling at the catchment scale, interacting with local stakeholders who were involved throughout the research, in line with current Land System research. First, we built contrasted scenarios, each with a narrative story and quantitative assumptions for key variables. Then we drew up rules for translating narrative scenarios into spatially explicit maps based on expert groups and local knowledge, simulating the evolution of land use over time. Third, we evaluated and validated the final scenarios by conducting two workshops with scientists and local stakeholders. Finally, we assessed the impact of these scenarios on agricultural production and erosion control. This approach was implemented in the Tleta basin (Morocco), a 180 km2 rural watershed, 10 km from Tangiers and heavily affected by water erosion. As a result, we propose three contrasted spatially explicit land-use change scenarios by 2040. Our work highlights the interest of combining narrative storylines and land-use modelling when developing spatially explicit scenarios at the catchment scale, incorporating the local knowledge of stakeholders. The combination of Land System and ecosystem frameworks contributes to integrating the soil erosion issue in a more global perspective, and lays the foundation for building sustainable strategies for Mediterranean catchments affected by soil erosion.