Analysis And Assessment Of Spatiotemporal Variations And Developments Of Water Footprints Of Pig Feeding And Pork Production In China(2004-2017)

With the change of dietary structure,the demand about meat food for people growing with the passage of time,and the production of animal products increasing accordingly.Moreover,the volume of feed consumption rising dramatically,and the extensive planting of feed crops has increased the pressure on agricultural water resources.The water footprint(WF)of livestock at slaughtered refers to the volume of direct and indirect freshwater consumed and contaminated by livestock feeding.The WF of livestock products is the sum of WFs based on animal WFs and the necessary process of livestock product processing.China is the largest producer of pork in the world,and pork is also chinese main livestock products.However,the sharp increase in pork production and the uneven spatial distribution of pork production in various regions,as well as the spatial inconsistency of crop planting,pig breeding,and distribution of water resources have brought huge challenges to China’s already severe water resources situation.In addition,the available blue water resources in most areas of China have been unable to meet the needs of human production and living,and the blue water footprint beyond the available blue water is regarded as"unsustainable blue water footprint".Therefore,to reveal the space-time evolution of pig and pork production water footprint,this study adopted the method of"bottom-up"to quantified the blue,green,and grey water footprint of pig feeding and pork production about 31 provinces of China’s mainland in 2004-2017,particularly the grey water footprint contains the grey water of forage planting process and the pig execrations.And the pig farming system is divided into scatter-feed scale,small scale,medium scale,and large scale.Besides,based on the concept of"sustainability of blue water footprint",the sustainability of water footprint of pigs and virtual water flows of feed were evaluated to determine the efficiency and impact of livestock production on regional water use in China.The main research results are as follows:(1)During the study period,the average consumptive WF(Water footprint)of pig per head and gray WF were 343 m3/head and 204 m3/head,respectively.In China,the average annual consumptive and degradative WFs of pigs is 225.4 Gm~3/a and 135.2 Gm~3/a respectively.(2)The water use efficiency of pigs gradually improved,but the total water consumption of pig feeding continued to increase.with the increase in the number of slaughtered pigs(14%),the annual consumptive and degradative WFs of pigs increased by 3%and 11%,respectively.(3)The impact of animal husbandry on water quality cannot be ignored.As the green,WF,and blue WF of each farming scale decreased verily,the gray WF of the small,medium,and large scale increased by 3%,5%,and 8%,respectively.Responding to intensive farming methods requires extra attention to the impact of livestock pollution.(4)Scale efficiency has a positive impact on the water use efficiency of pigs.Scatter-feed with the largest water footprint of pigs,while large-scale is the farming scale with the smallest water footprint of live pigs.If all pigs’feeding is changed to large-scale in 2017,13 Gm3(consumptive WF)and 10.3 Gm3(degradative WF)can be saved.In particular,although the water footprint of pigs in big-scale systems is the smallest,the grey water footprint of pigs is increasing.It is necessary to control the negative impact of pig excretion on the environment while encouraging large-scale farming system.(5)The virtual water flow of forage crops in China exacerbates the current situation of regional water shortage and uneven distribution,and water security challenges in water-deficient areas are severe.The unsustainable blue water footprint of pig feeding accounts for86%of the total,in which feed crops contributed to 91%.The higher water footprint of pig feeding is concentrated on the southern region,whereas the highest unsustainable blue water footprint of pig feeding focuses on the northern region with severe water shortage.The unsustainable blue virtual water exports from water-scarce provinces have reached 91%of overall feed crop-related inter-provincial blue virtual water flows by 2017.