Desertification is a global phenomenon that threatens both the environment and human societies, particularly in arid, semi-arid, and sub-humid areas. The upper Ziz watershed, located in the south-east of Morocco, represents a region particularly vulnerable to this process. The objective of this study is to analyze the spatio-temporal dynamics and spatial extent of desertification in this region over the period 2000-2024, based on the combined use of GIS and remote sensing techniques. The methodological approach relies on the construction of feature spaces for the development of desertification degree index (DDI). To this end, several spectral indices were derived from Landsat 7 and Landsat 9 imagery, including NDVI (normalized difference vegetation index), MSAVI (modified soil adjusted vegetation index), LST (land surface temperature), TGSI (topsoil grain size index), and albedo. In addition, the tasseled cap transformation (TCT) was applied to compute three main components: brightness (TCB), wetness (TCW), and greenness (TCG). Linear regression analysis revealed strong inverse relationships between soil moisture on the one hand and soil reflectance and brightness on the other, with the TCW-Albedo and TCB-TCW pairs showing the strongest negative correlations (- 0.87 and - 0.88 for 2000; - 0.78 and - 0.86 for 2024). These combinations were used to construct models, develop the DDI, and classify the study area into five desertification levels: extreme, severe, moderate, slight, and non-desertified. In 2000, 36.3% of the area was classified as severely to extremely desertified, 53.1% as moderately to slightly desertified, and only 10.6% remained non-affected. Field validation of the desertification classes yielded an overall accuracy of 85.71% and a Kappa coefficient of 0.79 for 2000, and 92.38% with a Kappa of 0.863 for 2024, confirming the reliability of the proposed models. Between 2000 and 2024, non-desertified areas decreased by 97.4 km(2) (- 19.53%), while extreme and moderate classes increased by 34.33 km(2) (+ 5.92%) and 86.97 km(2) (+ 6.49%), respectively. Conversely, the severe class decreased by 32.79 km(2) (- 2.89%), and the slight class showed a slight increase of 8.88 km(2) (+ 0.76%). These results confirm the effectiveness of the TCW-Albedo and TCB-TCW models for monitoring desertification dynamics in the Ziz region.