Environmental impact of grain virtual water flows in China: From 1997 to 2014

Abstract The mismatching of grain production and consumption in space causes grain virtual water flow. Previous studies focused on the important role of virtual water trade in regional food security and its impact on water resource consumption, while this study focuses on the impact of virtual water flow on the environment. In this paper, two indexes of gray water footprint and carbon footprint were selected by footprint evaluation method to study the influence of virtual water flow on regional environment. The results show that the scale of grain virtual water flow gradually expanded, and the amount of virtual water flow increased from 67.14 Gm³ to 129.87 Gm³ from 1997 to 2014. The gray water footprint at a national scale showed a fluctuating trend, with obvious differences in temporal and spatial distribution. In addition, the total carbon footprint at the national scale increased from 290.2 Mton in 1997–430.4 Mton in 2014, basically showing a continuous increase trend. Provinces with larger gray water footprints are basically converted into import areas, and the total national gray water footprint reduced 64.74 Gm3. Meanwhile, the carbon footprint of the grain export region and import region changed significantly. Among the export areas, such as the Northeast region and the Huang-Huai-Hai region, the carbon footprint had an obvious downward trend. On the other hand, the carbon footprint of the import region in the south due to increasing of grain production to meet their own needs showed an increasing trend. Although virtual water flow reduced the gray water footprint and carbon footprint nationally, it increased the local environmental pressure on the export area. This study would be helpful in forming better water management policy and alleviating regional environment pressure.