为了评估黄土丘陵区实施退耕还林工程对县域粮食安全的影响,选取研究区典型四县——米脂、清涧、子洲和吴堡,假设实施退耕还林工程粮食补贴全部以粮食实物兑现和不实施退耕还林工程退耕的坡耕地提供粮食生产为前提,运用修订的耕地压力指数模型来对比评估退耕还林工程对县域粮食安全的影响。研究结果表明:退耕还林工程对米脂县和子洲县粮食安全影响较明显,对清涧县和吴堡县影响甚微。不同退耕规模对不同人口密度县域粮食安全的影响程度不同。研究结果对国家建立长期、稳定、有效的粮食补偿机制有一定参考意义。

Since 1999, the government of China has carried out an awfully ambitious conservation program for "win-win" objective of environment refinement and poverty reduction becoming self-sustainable. The program was famous Grain for Green Project, for which the government of China spent more than 4300 billion yuan and 27 million hm² of slope cultivated land was converted to forest and more than 100 million farmers took part in the program from 1999 to 2008. So we adopted the revised model of land use pressure index to the assessment of Grain for Green Project on the county-level food security from 1999 to 2008 based on case study in Mizhi, Qingjian, Zizhou and Wupu counties. Supposed food subsidies to compensation loss of farmers conversed of cropland to forest land in the form of grain for framers conversed of forest land to cropland, the results indicates that the effects of Grain for Green Project on Mizhi and Zizhou counties, which have a population density of 150-180 people per km² and implementation conversion of 1.44-1.58 ten thousand hm² of cropland to forest land,are obvious; but that of Qingjian County with a population density of 110-120 people per km² and implementation conversion of 0.4 ten thousand hm² of cropland to forest land and Wupu County with a population density of 170-190 people per km² and implementation conversion of 0.4 ten thousand hm² of cropland to forest land, are little influenced. In a word, the effects on food safety for counties with different population density and different conversion scale are different in the Loess Plateau hilly region. The government will choose the results to establish long-term, stable and effective food compensation mechanism, in order to consolidate gains of Grain for Green Project in the future.