Study on Changing Relationship of Demand and Supply of Cultivated Land in China

The purpose of this study is to reveal the relationship and correlation of land supply for food security and land demand for urbanization-industrialization in China,so as to provide scientific basis for national land use policy.The main methods involve hypothesis verification.The hypotheses on minimum area of cultivated land per capita(reflecting cultivated land demand for food security)and on logistic equation of cultivated land conversion are put forward.The annual data of cultivated land are corrected and series of data during 1980 — 2006 are re-established.Hereby minimum area of cultivated land per capita and pressure index on cultivated land(the ratio between the supplyof and demand for cultivated land) are culculated.The research results demonstrate that the demand of cutivated land per capita for food security is decreasing gradually,the pressure index on cultivated land is generally in a downtrend.Under the conditions that the land demands for urbanization and industialization and for ecological construction have been met,thus land supply for food security has been decreased continuouslly,and population has increased at the same time,however the situation of food security is not worsening but improving,the pressure index on cultivated land is not aggravating but abating.The fundamentality is the continuously increase of land productivity.The cultivated land conversion for urbanization and industrialization impacts land supply for food security.This research deduced and proved the logistic equation process of cultivated land conversion.Two inflexions appear in 1980 and 2050,the former is the turning point from gentle increase to acceleration,and the latter is the turning point from growth to stagnant suggesting the land supply for food security will tend to stable.There is another inflexion between them,that is the turning point from acceleration to slowdown in 2015.In conclusion,the demands for urbanization-industialization and food security may be met at all.