Spatial–Temporal Changes and Driving Forces of Sandy Desertification in Dengkou County, China, Based on Refined Interpretation and Validation

Sandy desertification is a major ecological and environmental challenge worldwide, posing a severe threat to ecological security in arid regions. A systematic understanding of the spatial–temporal dynamics of sandy desertification and their driving forces enables effective support for ecological engineering in China. We visually interpreted five Landsat imaging periods (1986–2023) to map sandy desert areas (SDA), which were confirmed by 176 field samples. Driving forces were measured using the Geographical Detector model, and changes in the extent and intensity of SDA were evaluated using intensity analysis and center of gravity migration. The results indicate the following: (1) On the temporal scale, sandy desertification land in Dengkou County experienced a significant reversal over the past 40 years, with a total reduction of 1204.72 km2. On the spatial scale, the main areas of reduction were located in the central and southwestern regions. (2) Sandy desertification in Dengkou County underwent a process of initial reversal, followed by expansion, and then another reversal. The periods 1986–1995 and 2004–2023 were reversal phases, while 1995–2004 was a development phase. (3) Livestock density showed the strongest influence among anthropogenic factors (q = 0.224), suggesting a strong correlation with sandy desertification patterns. Among natural factors, geological conditions exert the most significant influence (q = 0.182). Every pair of driving factors, with the exception of slope aspect and soil moisture, showed either additive or synergistic effects, increasing their combined influence on desertification. The results provide a scientific basis for local ecological restoration and desertification control.