A participatory GIS approach to identify critical land degradation areas and prioritize soil conservation for mountainous olive groves (case study)

Climate change scenarios predict an increase in the frequency of heavy rainfall events in some areas. This will increase runoff and soil erosion, and reduce agricultural productivity, particularly on vulnerable mountainous agricultural lands that is already exhibiting high rates of soil erosion. Haphazard implementation of soil and water conservation (SWC) interventions on scattered fields is inefficient in reducing soil erosion. The objective of this study was to identify areas at high risk of erosion to aid the design and implementation of sustainable SWC using GIS analysis and farmers' participation approach. A 25 m digital elevation model (DEM) was used to derive layers of flow accumulation, slope steepness and land curvature, which were used to derive an erosion-risk (priority) map for the whole watershed. Boundaries of farmers' fields were mapped and verified by the community and each field was classified into high, moderate or low erosion risk. Fields with low flow accumulation (top of hill) and/or steep slope and/or convex slope were assigned high erosion risk and therefore high implementation priority. The study showed that more than 64% of the fields were classified into high erosion risk areas. Accordingly, a community-watershed plan was established, revised and approved by the community. Incentive loans to implement SWC measures were distributed to 100 farmers based on the priorities of their fields. Judged by local farmers and using 16 randomly selected fields, 90% of the targeted areas were correctly identified using the erosion risk map. After two years, the conservation measures had led to marked improvement of soil conservation. The approach is simple and easy to comprehend by the community and provides scientific basis to prioritize the implementation of SWC and to target the most degraded areas, which amplify the impact of these in reducing the vulnerability to land degradation.