Combining foresight, local knowledge and land use change modeling to anticipate future landscape services at the catchment scale

Mediterranean soil resources are heavily affected by water erosion that may lead to a decrease in soil fertility affecting agricultural production, and to an accelerated rate of siltation in water reservoirs. There is a need to anticipate the potential impacts of global change, in order to prepare relevant adaptation strategies. While foresight approaches are promising, their outputs generally take the form of narrative storylines which may be difficult to link to spatially distributed biophysical models used to simulate soil and water processes.

We address this challenge by developing a systemic approach that combines the use of scenario workshops with quantitative approaches (surveys with farmers and institutional stakeholders, statistics, satellite images), land use and land cover change modelling and hydrological modelling for simulating impacts of global changes on soil resources and landscape services. This approach is implemented to the Tleta basin (Morocco), a 180 km² rural watershed affected by important soil degradation due to water erosion.

As a result, we propose three plausible future land use scenarios by 2040. The first scenario Urbanisation and industrial development considers a high urbanisation rate in the plain and a decrease in agricultural areas. The second scenario The fruit basket of Tleta assumes an important development of the arboriculture (olive, grape, pomegranate and fig trees) mostly in the plain, with a lower urbanisation rate. The third scenario One foot in the city, one foot in the countryside envisions the development of farming systems with high added value and quality local products in the hillslopes, benefiting from the proximity of Tanger. Each scenario includes a narrative, future land use maps up to 2040, and a set of quantified socio-economic variables.

These scenarios serve as an input to the SWAT hydrological model for assess the evolution of runoff and soil resources degradation, and to the valuation of three landscape services delivered at the basin level: agricultural production, erosion control and water storage. From a methodological perspective, the research highlights the interest of combining narrative storylines and quantitative approaches to develop spatially explicit scenarios at the catchment scale that account for the local knowledge of stakeholders.