County-level cropland fragmentation in China (1990–2023): a bidirectional transformation perspective

Cropland fragmentation (CLF) studies often overlook bidirectional land transformations. This study reassesses county-level CLF in China (1990–2023) using a 30 m-resolution Landsat-based dataset and a novel Modified Landscape Division Index (MLDI) to capture both cropland gains (transfer-in) and losses (transfer-out). We find pronounced CLF increases in urbanized plains, notably the Huang-Huai-Hai Plain (6.13×10⁻²/y), Northeast China Plain (3.69×10⁻²/y), and Sichuan Basin (4.97×10⁻²/y), driven primarily by urbanization (39.5% contribution to CLF from impervious surfaces). Conversely, cropland gains from forests and grasslands mitigate fragmentation, with forest-to-cropland conversion reducing CLF by 40.3%. Counties with CLF increases due to losses outnumber those with decreases by 5.5 times. Regression analysis reveals strong correlations between area changes and CLF (p < 0.01). These insights are relevant for urbanizing regions globally, such as Southeast Asia and Sub-Saharan Africa, highlighting the need for policies like zoning regulations and reforestation incentives to balance urban expansion with cropland restoration for sustainable land use and food security.