Can traditional forest management buffer forest depletion? Dynamics of Moroccan High Atlas Mountain forests using remote sensing and vegetation analysis

▶ High resolution remote sensing shows subtle changes in percentage canopy cover. ▶ Significant forest degradation occurred between 1964 and 2002. ▶ Traditionally managed forest patches (“Agdal”) show a significantly better state. ▶Agdal alone is not sufficient to reach a viable management mode in the long term. On the south shore of the western Mediterranean Basin, mountain forest ecosystems are degraded, mainly due to their overexploitation. Topographic, edaphic and climatic conditions create stressful growing conditions and sensitive ecosystems. Nonetheless, in these ecosystems, forests remain an important resource for the subsistence of local populations. Historically the vulnerability of this resource has prompted mankind to establish traditional control forms of forest and pastoral areas. These common resource management systems are still functioning in the Moroccan High Atlas Mountains under the name of agdal which refers to the territory, the resources and access rules laid down by the local population in order to manage the territory. The estimation of land cover changes was a suitable method to evaluate the effectiveness of these community-based systems for forest conservation. In this paper we highlight the impact of this traditional management on woodland dynamics in a mountainous area (Aït Bouguemez Valley) through the use of remote sensing approaches, associated with forest structure characterisation and the analysis of social mechanisms. A diachronic analysis based on the comparison of aerial photographs (dated 1964) with a recent Spot 5 satellite image (from 2002, 2.5m resolution) was performed. Estimation of changes in canopy cover percentage was achieved using a graphic chart as a base for the photo-interpretation, and a subsequent validation by field sampling. A map of canopy cover changes between 1964 and 2002 was produced. Ecological measurements of trees were also achieved on field plots. The results indicate that in the past 38 years, forest ecosystems have been affected by a relative decrease of 20.7% of the total forest area, and 8.7% for the mean canopy cover percentage. However, strong disparities in forest dynamics arose according to the agdal or non-agdal status of the forest. Significant progression in canopy cover is noted in controlled agdal areas but large degradation has occurred outside. Regarding the stand ecological conditions, we observed significant differences in the stand structure, according to the management mode.