How to minimize the impacts of urban expansion on farmland loss: developing a few large or many small cities?

Context: In China, large cities are often held to blame for the drastic loss of high-quality farmland. However, others propose that the development of large cities should be prioritized for their scale economy in saving farmland. A policy debate remains regarding which urbanization mode—developing a few large or many small cities—can minimize the impacts of urban expansion on farmland loss. Objective: The present study aims to clarify the controversy by quantifying the quantity and quality of urbanization-encroached farmland (UEF) in different sizes of cities. Methods: We proposed two indexes to quantify the UEF among different sizes of cities during 2000–2010: “the UEF area per urban population growth” and “the average potential yield of UEF”. Furthermore, we proposed a spatial prioritization matrix to facilitate place-based policy design for UEF management. Results: The super large cities (SLC) consumed the least UEF area per urban population growth and also the lowest average potential yield of UEF. However, there were large variations within city categories in both the quality and quantity dimensions. Farmland loss to urban expansion is determined by a city’s biophysical and socio-political conditions. Conclusions: Our analyses show that urban growth of SLC consumed smaller quantity of farmland when accommodating a certain amount of urban population. Containing the development of large cities in the name of food security is ineffective, which will cause double failures in farmland preservation and urban development. As the impacts of urban expansion on farmland loss are highly place-variant and urban sustainability is more than just food security, place-based policies following the landscape sustainability perspective are needed to address urban encroachment of farmland.