Spatio-Temporal Dynamics and Driving Mechanisms of Cropland Fragmentation and Habitat Quality in Hunan Province, China (1994–2024)

Cropland fragmentation affects regional ecosystem functioning and biodiversity conservation, making the spatio-temporal coupling between cropland fragmentation (CLF) and habitat quality (HQ) a key basis for land management and ecological protection. However, the reported CLF–HQ coupling differs in sign between regions, and the mechanism underlying this divergence remains unclear. This study evaluated the spatio-temporal dynamics of CLF and HQ and their interrelationship across Hunan Province, China, at the township scale (∼2450 units) from 1994 to 2024. CLF was measured by a four-dimensional index consisting of Scale (SPI), Natural Endowment (NPI), Aggregation (API), and Convenience (CPI), with weights determined by a combined AHP–Entropy method; HQ was modelled with InVEST. The relationship between the two was analysed through bivariate spatial autocorrelation, Mantel tests, Random Forest, redundancy analysis (RDA), and XGBoost–SHAP. CLF peaked in urban fringes and was lowest in the western mountains; mean HQ declined modestly, mainly before 2014. Spatially, CLF and HQ were negatively associated (bivariate Moran’s I between −0.38 and −0.51, p<0.001), opposite in sign to the positive coupling found in arid Northwest China. Decomposition of the composite index showed that the negative association was carried largely by the natural-endowment dimension, in which slope and elevation were the dominant indicators. Structural fragmentation dimensions uniquely explained only 1.5–5.4% of HQ variance, and controlling for terrain reduced the CLF–HQ correlation by 67–96%. The sign also reversed under an alternative directional standardisation, so it is not robust to a defensible analytical choice. In these data, the observed negative coupling is largely consistent with a shared topographic gradient rather than a direct fragmentation effect. For management, this correlational evidence suggests that reducing fragmentation alone may do little to improve habitat quality; conservation is better guided by the underlying terrain and land-use gradients. More broadly, CLF–HQ assessments become more reliable when cropland structure is separated from natural endowment and terrain confounding is accounted for.