南方水稻复种指数变化对国家粮食产能的影响及其政策启示

The impact of paddy rice multiple cropping index changes in Southern China on national grain production capacity and its policy implications

中国南方地区水稻生产的变化对国家粮食安全具有重要影响。本文利用Landsat数据提取1990-2015年南方地区水稻种植制度分布及变化,并分析其对粮食产能的影响。结果表明:①1990-2015年,水稻复种指数从148.3%下降到129.3%,双季稻改种单季稻("双改单")损失的播种面积为253.16万hm^2,区域上以长江中下游地区变化最为突出。南方地区水稻种植制度整体呈现由北向南"双退单进"的变化格局;②1990-2015年,"双改单"导致全国水稻产量减少6.1%,粮食产量减少2.6%。水稻主产区湖南省和江西省以及经济发展较好的浙江省因"双改单"水稻减产幅度较大,均超过13%;③充分利用"双改单"稻田的粮食产能相当于新增耕地223.3万hm^2,为2001-2015年通过土地整治项目新增耕地总量的54%,是2016-2020年全国新增耕地规划目标的1.7倍,可节省约1674.4亿元新增耕地开垦费用。因此,与其追求低质量的"新"耕地,不如充分利用已有的高质量"旧"耕地,政府应转变耕地占补平衡的考核方式,将因提高复种指数增加的播种面积纳入补充指标。

Changes of rice production in Southern China are crucial to national food security.This study employed Landsat images to map the distributions of paddy rice cropping systems in Southern China in 1990 and 2015,and then explored the impact of rice multiple cropping index changes on grain production capacity.The results indicated that:(1)From 1990 to 2015,the multiple cropping index of rice decreased from 148.3%to 129.3%,and the loss area due to conversion of double cropping rice to single cropping rice("double to single")was 253.16×104 hm^2.The area with most dramatic changes was located in the Middle-Lower Yangtze Plain.The rice cropping systems in Southern China showed a change pattern of"double cropping rice shrinkage and single cropping rice expansion"from north to south.(2)From 1990 to 2015,"double to single"led to a reduction of 6.1%and 2.6%in rice production and grain production,respectively.Hunan and Jiangxi,located in the main rice producing areas,as well as Zhejiang with better economic development,had a large reduction in rice production due to"double to single",all exceeding 13%.(3)The grain production capacity of"double to single"paddy field is equivalent to that of 223.3×104 hm^2 of newly reclaimed cultivated land.The equivalent newly reclaimed cultivated land is 54%of the total newly reclaimed cultivated land through the land consolidation project during 2001-2015,as well as 1.7 times the target of the newly cultivated land goal for the national land consolidation plan(2016-2020).Making full use of the"double to single"paddy field can save approximately 167.44 billion yuan newly reclaimed cultivated land costs.Therefore,instead of pursuing low-quality"new"arable land,it is better to make full use of the existing high-quality"old"arable land.The government should change the assessment method of cultivated land balance,and incorporate the sown area increased by improving multiple cropping index into the cultivated land compensation indicator.