Dynamics of Paddy Field Patterns in Response to Urbanization: A Case Study of the Hang-Jia-Hu Plain

Urban land has increasingly expanded and encroached upon a significant number of paddy fields in Hang-Jia-Hu Plain, due to the rapid socio-economic development and agro-pedoclimatic conditions favorable to rice cultivation and human settlement. Although many studies have analyzed the characteristics of urban land expansion, relatively less attention has been paid to exploring the various urban expansion patterns and the impact of different urban expansion patterns on paddy field at a regional scale. This paper characterized the changing patterns of paddy fields in response to various urban expansion patterns in the Hang-Jia-Hu Plain integrating geographic information systems, gradient analyses and landscape metrics. Our results demonstrate that the amount of urban land expanded to nearly four times that of the initial area during 1980-2010 and that 88% of new urban land was developed on paddy fields. Of the total area of paddy fields, paddy fields of level I accounted for 96%. Moreover, various urban expansion styles differentially influenced the patterns of paddy fields. In autonomous expansion cities, sprawled urban land mainly occupied paddy fields in urban centers. However, the irregular expansion of passive expansion cities encroached on a number of paddy fields in the urban fringe where the landscape of urban patches and paddy fields was more complex and irregular in shape. Furthermore, the urbanization curve implies that future urbanization efforts will focus on the passive expansion cities, indicating that paddy fields still face the risk of disruption. We suggest that the boundary of urban development should be restricted, permanent paddy reserves should be delimited, and ecologically oriented management systems that target paddy field protection should be implemented to ensure the sustainable development of this region. This work improved the understanding of the urbanization process that governed paddy fields dynamics, and provides a scientific basis for decision-making processes to achieve regional sustainability.