How does urban expansion interact with cropland loss? A comparison of 14 Chinese cities from 1980 to 2015

Context Characterized by intensive urban sprawl and continuous cropland shrinkage, the unprecedented urbanization process has profoundly reshaped China's landscape over the past four decades. However, the interaction between urban expansion and cropland loss in China at a finer spatiotemporal resolution remains unclear. Objectives This study aims to quantify and compare the rates, patterns, dynamics, and interactions of urban expansion and cropland loss in 14 Chinese cities during 1980-2015. Methods Multiple landscape metrics were calculated to quantify the magnitudes, rates, and patterns of urban expansion and cropland loss for each city. The standard deviation ellipse analysis and two quantitative indices (the dependence and the contribution of urban expansion on cropland loss) were used to characterize the relationship between urban expansion and cropland loss. Results The pattern of rapid urban expansion and extensive cropland loss was observed across all selected cities (except for Harbin), with the averaged expansion area of 764.17 km(2)and averaged loss area of 650.83 km(2)per city. The primary mode of urbanization was the edge-expansion (6889.22 km(2), 60.01%), followed by the infilling (2767.32 km(2), 24,11%) and the outlying (1822.72 km(2), 15.88%). Urban expansion was identified to be the dominant driver of cropland loss, accounting for 84.99% of the newly expanded urban land and 74.36% of the lost cropland in total, thus leading to a more spatially irregular and fragmented distribution of the cropland. Conclusions The balance between urbanization and land protection is still challenging. Here we advocate more effective policy-driven practices to protect China's existing cropland for food security and sustainable development goals.