Quantifying urban expansion and agricultural land conversion using spatial indices: evidence from the Red River Delta, Vietnam

Urban expansion in rapidly developing detlas often occurs at the expense of fertile agricultural land, posing challenges to food security and sustainable land management. This study quantitatively assesses the spatial relationship between urban growth and agricultural land loss in the Red River Delta (RRD), Vietnam, during 2017–2024, using the ESRI 10 m Land Cover dataset derived from Sentinel-2 imagery. A land-use conversion matrix was constructed, and two spatial indices were developed: the D index, representing the dependence of urban expansion on agricultural land, and the C index, reflecting the contribution of farmland conversion to urban growth. In addition, Getis-Ord Gi* hotspot analysis was applied to identify spatial clusters of built-up land expansion. The results reveal that built-up land increased by approximately 161,000 ha, while agricultural land decreased by about 152,000 ha, with 116,514 ha directly converted from farmland. Hotspot analysis indicates significant clustering of urban expansion around Hanoi, Hai Phong, and neighboring peri-urban zones. High D and C values (above 60 %) dominate much of region, confirming the spatial dependence of new urban areas on agricultural land conversion. These findings provide updated quantitative evidence for land-use transitions in Vietnam’s key delta region and highlight the importance of spatial monitoring tools in supporting policies toward sustainable urban and agricultural development.