Abstract: The recent global food security crisis is garnering increasing attention and calls for innovative solutions to mitigate its negative impacts on people, especially the most economically vulnerable.In urban regions, this issue is aggravated by the fact that, on one hand, rapid urbanization and greater levels and diversity of food consumption associated with the growing affluence of urban inhabitants has led to rising urban food demand, while on the other hand, the rapid loss of farmland due to urban expansion or irrational sprawl and increasing extreme weather events for agricultural producers due to the impact of global climate change is sharply reducing the urban food production and local supply capacity.Therefore how to realize the urban food supply potential and optimize the utilization of the urban farmlands to enhance the local food supply rate and improve urban food security more generally is becoming a key issue.In this paper, we use the case of Beijing to examine the opportunities to enhance the supply of local, affordably priced food under existing land resource constraints, by restructuring farmland utilization.In this paper, we firstly calculate the changes in the food footprint needed by Beijing and its food self-sufficiency rate over the thirty year period from 1981 to 2011.We show that although Beijing's food footprint has grown from 11 800 to 29 400 km² over this 30-year period, its food self-sufficiency rate has dropped from 59.3%, 35.8%, 37.3% and 13.1% to about 39.0%, 27.0%, 6.7% and 2.2% for vegetable, fruit, grain and edible oil, respectively.Following this analysis, we calculate Beijing's potential food production under different agricultural production allocation scenarios.We conclude that with a proper shift of farmland use, full utilization of temporary idle land, and the development of rooftop farming, Beijing could increase its vegetable self-sufficiency rate to 60% without significantly reducing the production of other types of local food.Given the sensitivity of fresh vegetables to long-distance transport, and the potential to reduce transport-related carbon emissions, this is a worthwhile adjustment that will benefit the city both by meeting the growing need of its residents for fresh food, and by improving the overall regional eco-environment.

Key words: food footprint, food self-sufficiency, local food production, urban agriculture, constrained land resource