Modélisation de la vulnérabilité à la désertification dans le contexte des changements globaux au Maroc (Cas de l’arganeraie à Essaouira et Tiznit et des écosystèmes dunaires à Errachidia)

Abstract

Desertification affects almost half of the planet’s surface (41%). Despite the extent of the phenomenon, desertification is still little mastered. The main objective of this thesis is to assess the phenomenon of desertification in the form in which it occurs in the most vulnerable ecosystems in Morocco. The aim is to understand the functioning of these ecosystems in order to propose specific strategic solutions to strengthen the adaptive capacity of the local population and the resilience of the biophysical environment against climate change and anthropogenic pressure. To this end, a description of the current state of knowledge on desertification was presented, followed by the identification of the most vulnerable areas to desertification in Morocco using the multi-criteria analysis by the weighted sum method. Finally, a more in-depth assessment of desertification was carried out in two Morocco’s characteristic ecosystems, namely the argan tree area in the southwest (in Essaouira and Tiznit) and the dune ecosystems in the east (in Errachidia). In the argan tree area, there has been an increase in the area occupied by cultivated land under argan trees to the detriment of natural argan ecosystems, especially in low-slope areas (<5%). In Errachidia, the use of the Seasonal Autoregressive Integrated with Moving Average (SARIMA) model revealed an increase in the extent of sand dunes at a rate of 1.7% per year. This increase would be mainly caused by the combined effect of climatic factors fluctuating from year to year.