Mapping and monitoring spatiotemporal desertification patterns in the arid transition zone of Algeria over the period 2002–2022

Desertification represents a critical threat to ecosystems, agriculture, and livelihoods in arid and semi-arid regions. This study provides a comprehensive analysis of the spatio-temporal evolution of desertification across Algeria’s steppic and northern Sahara regions from 2002 to 2022. Using Earth observation data and cloud-based processing platforms, we developed an analytical workflow1 that combines multitemporal vegetation sparsity mapping and desertification trend analysis. Our approach employed a derived composite index, the Vegetation Sparsity Index (VSI), along with intensity analysis, gravity center change, and regionalization-based clustering. The results showed that desertification dynamics in the study area are not uniform, but characterized by distinct phases of degradation and revegetation. Specifically, desertified areas expanded northward in the western and central regions from 2010, with the central western region, which is vital for agriculture and pastoralism, degraded beyond what rainfall trends alone would predict. In contrast, the eastern regions showed significant greening. These results underscore the heterogeneous nature of desertification in the region and provide critical insights for targeted mitigation efforts.