In semi-arid regions, desertification is a critical environmental degradation factor. This study analyzes land degradation and desertification vulnerability dynamics in Ningxia, China (2001–2022) using the MEDALUS framework with a Random Forest classifier. Land-cover change was significant due to irrigation and agricultural expansion, with farmland increasing to 65.29% of the landscape while grassland shrank to 10.13%, intensifying ecological pressure. Bare land followed a U-shaped trend, reaching 9.17% in 2022, indicating increased soil exposure. Soil quality remained moderately stable, with 70–80% of land retaining integrity despite ongoing degradation. Vegetation quality fluctuated considerably, as poor vegetation quality decreased from 42.42% in 2001 to 36.6% in 2022, with scattered local recovery. Management quality improved due to irrigation modernization and policy implementation, while long-term aridity moderately constrained climatic conditions. The Desertification Sensitivity Index (DSI) varied over time: low-desertification areas accounted for 44.47% in 2001, while high-desertification areas comprised 29.06%. By 2011, conservation efforts increased stable areas to 48.26%. However, in 2022, high-desertification areas persisted across 9,552.49 km², primarily in northern and central regions characterized by poor soil and uneven rainfall. This research provides robust scientific evidence to inform land management, vegetation rehabilitation, and climate adaptation strategies in vulnerable drylands.