Impacts of in situ urbanisation on grain production: Evidence from the Yangtze River Delta, China

With the promotion of county-level urban-rural integrated development policies in China, counties in economically developed regions have achieved sound in situ urbanisation (ISU), resulting in changes in regional population and production structures. However, to date, relatively few studies have focused on the ISU process and the variation in regional grain production in the Yangtze River Delta (YRD). This study evaluated the ISU rate (ISUR) at the county level using the entropy based TOPSIS model, introduced a super efficiency slacks-based measure (SBM) model to calculate cropland production efficiency (CPE), and reflected the status of grain production from grain yield and CPE. Spatio-temporal dynamics of ISU and grain production were examined from 2000 to 2020, and the impact mechanism of ISU on the grain production were explored encompassing regional differences and spatiotemporal evolution. The ISUR of the YRD showed a high distribution in the east and low in the west, with all counties showing a continuous increase, and an average increase from 0.15 in 2010 to 0.33 in 2020. The most rapid increases occurred in northern Zhejiang, southern Jiangsu, and the coastal areas. The grain yield in the entire region was high in the north and low in the south, with a continuous increase in the north and a continuous decrease in the south. The CPE distribution changed from high in the south in 2000 to high in the north in 2020, with a higher growth rate in the north and a significant decrease in the south. The initial advancement of ISU promoted grain production. The plains with medium ISU levels showed the highest grain yield and CPE. Where the ISU level reached extremely high levels, it had a suppressive effect on grain production. In mountainous areas, the CPE and grain yield decreased during ISU. The findings of this study are of great value to policymakers in adjusting the regional agricultural production structure according to ISU stages to implement food security strategies in a regionally integrated manner.