Evolution of forest and land coverage from 1964 to 2002 in the high valley of Ait Bouguemez (Central High Atlas, Morocco). Impact of management modes. (Surveillance environnementale a long terme dans les zones arides et semi-arides (Long-term environ

摘要

In Mediterranean mountains, forest ecosystems are often harshly degraded due to overexploitation. The vulnerability of these resources has prompted the establishment of traditional forms of control of forests and pastoral areas. These management systems are still functioning in the Moroccan High Atlas under the name of agdal. This term refers both to the territory, the resources and the access rules laid down by the local population in order to manage the territory. The purpose of this study is to assess the impact of this customary management on woodland dynamics in a mountainous area, the Ait Bouguemez valley, through a diachronic analysis based on the comparison of old documents (aerial photographs from 1964) with recent documents (Spot 5 very high resolution satellite images from 2002). The adopted methodology consists of the visual photointerpretation of the above mentioned documents while referring to a common charter to estimate the woody coverage. Two coverage maps are produced, one for 1964 and one for 2002. Overlaying them makes it possible to generate a map of the dynamics of the area. The results show strong disparities in the forest dynamics according to the agdal or non-agdal status of the forest. On the whole or the studied zone, the forested area has decreased by 21% over the 38 years under study. The average wooded percentage coverage has fallen from 20% to 18% based on the 1964 coverage, with maintenance of coverage in the controlled agdal zones and large scale degradation outside the agdal zones.