Spatio-temporal evolution and driving factors of land degradation in Deyang City, Sichuan province

Deyang City, situated in a typical mountain-plain transition zone of Southwest China, faces high ecological fragility due to its steep topographic gradient, frequent seismic disturbances (e.g., the 2008 Wenchuan earthquake), and intensive anthropogenic pressures from rapid urbanization and agricultural production. Taking this representative area as a case study, this study utilized multi-source remote sensing data from 2000, 2005, 2010, 2015, and 2020. A comprehensive Land Degradation Index (LDI) was constructed by integrating NDVI, Surface Albedo, Salinity Index, and Land Surface Temperature. Using transition matrix, Theil-Sen median trend analysis with Mann-Kendall tests, Geodetector models, and Coefficient of Variation (CV), we systematically diagnosed the spatio-temporal evolution, trends, stability, and driving factors of land degradation. The results show that: (1) From 2000 to 2020, the LDI exhibited a spatial pattern of “higher in the northwest, high and dispersed in the center, and low in the southeast.” The combined proportion of “Low” and “Slight” degradation rose from 43.33% to 62.86%, though a distinct rebound occurred in 2010 due to the Wenchuan earthquake. (2) Transition matrix analysis revealed a positive evolution, with the L1 grade increasing by 18.01%, reflecting long-term ecological recovery. (3) Trend analysis indicated a regional LDI decline (β = −0.0173/5years), with improvement areas (31.16%) exceeding degradation areas (12.13%). (4) Geodetector results identified temperature and precipitation as foundational drivers, while per capita GDP and population density gained explanatory power during rapid economic expansion. Universal bivariate and nonlinear enhancements suggest land degradation results from complex multi-factor coupling. (5) CV analysis showed high stability (90.75% of area with CV < 0.1), but the northwestern mountain-plain transition zone exhibited elevated ecological vulnerability due to seismic disturbance and human activities. This study provides an analytical framework for diagnosing land degradation in mountain-plain composite regions, offering a scientific basis for ecological restoration and sustainable land management policies.