Rural settlement expansion and paddy soil loss across an ex-urbanizing watershed in eastern coastal China during market transition

Historically, paddy soils are the most valuable natural resources that produce about 90% of staple food in eastern coastal China. Dispersed patterns of rapid rural settlement expansion, or "exurban", are recognized as key threats to the region's food security through paddy soil loss. Analyzing the process of ex-urbanization and its impact has profound implications for the sustainable development of rural China. Based on official statistics and data derived from satellite images, dynamics of rural settlement expansion and paddy soil loss were outlined for Tiaoxi watershed during China's market transition period (1994-2003). Particularly, rural settlements became more aggregated and total area expanded by 183% at an average rate of 12.3% per year for the whole watershed. Existing cores, open areas away from urban centers and areas near major transportation lines and river channels, observed the highest specialization in rural residential growth. Being closely associated with rural settlement in spatial distribution, open large paddy soil patches acted as another kind of center for rural settlement expansion within the landscape. Variations in rural settlement expansion were detected among different-tier counties, such as speed of rural settlement expansion, speed of build-ups growth per capita. These variations were closely related to social-economic development. The rapid rural settlement expansion led to a considerable loss of paddy soil, about 11% of the total amount for the whole watershed. Linear regression identified a significant relationship between paddy soil loss and rural settlement expansion. Given the social and ecological problems associated with paddy soil loss, we argue that innovative and effective planning policies as well as management programs that target at paddy soil protection should be developed and implemented in rural China. In particular, we suggest using watershed as an appropriate spatial unit for sustainable paddy soil management in this investigation.