AG引ADVANCINGEARTHANDSPACE SCIENCEWater Resources ResearchRESEARCH ARTICLEWater Footprints,Intra-National Virtual Water Flows,and10.10292021WR029809Associated Sustainability Related to Pork Production andConsumption:A Case for Chinaequally to this work.Xiangxiang Ji',Dong Xie 23,La Zhuo'4,Yilin Liu',Bianbian Feng',and Pute Wu4Key Points:.Over 80%of the blue water footprintNorthwest A F University,Yangling.China,2School of Environment,Harbin Institute of Technology,Harbin,China,of pork production in China isSchool of Environmental Science and Engineering.Southern University of Science and Technology,Shenzhen,China,4Institute of Soil and Water Conservation,Chinese Academy of Sciences Ministry of Water Resources,Yangling.China.One-third of pork-related scarce wateris consumed in low-water-scarceprovincesAbstract Growth in water consumption with intensified virtual water(VW)flows from increasedOne-fifth of the north-to-south virtualwater embodied in feed returns byproduction and consumption of both meat and feed crops threatens the sustainability of water resources inporkwater-scarce countries and export regions.However,a sustainability assessment of both water footprints (WFs)and VW flows related to animal products at a subnational scale is lacking.Here we estimate direct and indirectSupporting Information:WFs as well as the inter-provincial VW flows associated with pork production and consumption in China forthe years 2008 and 2017.The contributions of feed crop production and consumption were identified.Boththe online version of this article.life cycle assessment and WF network frameworks were applied to evaluate the sustainability of blue WF andVW flows.Results show that the national annual consumptive(green-blue)WF and degradative(gray)WF ofCorrespondence to:pork production increased by 8.7%and 15.8%.respectively.More than 80%of the blue WF in pork productionL.Zhuo and P.Wu,was unsustainable.By 2017,62%of the unsustainable blue WF and 64%of the water scarcity footprints ofzhuola@nwafu.edu.cn:pork production in the south resulted from consuming the feed crops from the north.This analysis highlightsgjzwpt@vip.sina.comthe importance and provides feasible approaches to uncover remote geographical effects on regional waterscarcities from different steps in the value chains of livestock products.Citation:Ji X.Xie,D.,Zhuo,L.,Liu,Y.,Feng.B..Wu,P.(2022).Water footprints1.Introductionintra-national virtual water flows,andassociated sustainability related to porkThe livestock industry consumes 35%of global crop production(FAO,2020),alongside one-third of the world'sproduction and consumption:A caseagricultural water consumption (Hoekstra Mekonnen,2012)and one-fifth of the international virtual water58,e2021WR029809.https://doi.(VW)trade in food (Hanasakiet al.,2010).Driven by growth in both individual consumption demand and popu-org/10.1029/2021WR029809lation in middle-income countries by 19%and 29%,respectively,from 2008 to 2017(FAO,2020),the continuousincrease in meat production and trade will undoubtedly exacerbate the water crisis in producing and exportingcountries that are already facing water shortages.This will lead to difficulties in ensuring the security of foodAccepted 5 JAN 2022and animal feed production under limited water and land resources (Chung et al..2020:Godfray et al..2018).Author Contributions:The water footprint(WF)of animal products measures the quantity of freshwater consumed in the production ofConceptualization:La Zhuo,Pute Wuanimal products and their impact on the water environment(Hoekstra et al.,2011).The WF of livestock feedingData curation:Yilin Liu,Bianbian Fengconsists of direct and indirect WFs.The direct WF consists of the water used for drinking and other services,Methodology:Xiangxiang Ji,Dong Xie,La Zhuoand for diluting concentrations of contaminants in animal excrement.Indirect WF measures the water appro-Resources:Bianbian Fengpriation associated with producing feed crops that are consumed during the livestock feeding cycle (Hoekstra,Software:Xiangxiang Ji,Dong Xieet al.,2011).Depending on different sources of water resources,the WF can also be categorized by blue WF (i.e.Supervision:La Zhuo,Pute WuValidation:Yilin Liu,Bianbian Fengsurface and groundwater),green WF(i.e.,rainwater),and gray WF(i.e.,water required to assimilate anthropo-genic loads of pollutants to freshwater bodies).The blue and green WFs are further categorized as consumptiveWFs,and the gray WF is the degradative WF(Hoekstra,2013).Several studies have quantified and analyzed the spatiotemporal evolvements in the WF of animal products atdifferent spatial scales.Gerbens-Leenes et al.(2013)demonstrated that WFs of meat production were driven byfeed conversion efficiencies,feed composition,and feed origin in the cases for China,Brazil and the United States2022.The Authors.This is an open access article underIbidhi et al.(2017)revealed that the average WF of chicken meat(6.0 m3 kg-)was smaller than that of sheepthe terms of the Creative Commonsmeat(18.9 m3 kg-),which was the smallest in the agro-pastoral system in Tunisia.Mekonnen et al.(2019)foundAttribution License,which permits usethat the combined effect of increased animal productivity and increased feed crop yields led to a decrease in thedistribution and reproduction in anymedium,provided the original work isaverage WF of animal feed,which resulted in a 36%decrease in the total WF production of animal products in theproperly cited.United States from 1960 to 2016.Xie et al.(2020)quantified the spatiotemporal evolution of the WF of pork atJI ET AL1of18AGUWater Resources Research10.1029/2021WR029809Writing -original draft:Xiangxiang Ji.the provincial scale under different farming scales within China over the period 2000-2014.However.few studiesDong Xiehave quantified the VW flows induced by the consumption of animal products and their intrinsic relationships withWriting-review editing:La Zhuo.Pute Wuthe WF and the VW flow related to feed crops.Only Hanasaki et al.(2010)and Dalin et al.(2014)clarified theinternational trade of major meat products and the inter-provincial VW flow in China,respectively,but there is alack of information on the VW flows directly associated with feed trade and consumption.This lack of informationprevents the exploration of regions that actually pay for the water consumed in the production of animal products.Only one such study exists by Zhuo et al.(2019),who estimated inter-provincial maize-related VWflows in China.and distinguished between consumption for food and feed.Two frameworks exist for assessing the impact of the WF on blue water resources,including the WF network(WFN)framework (Hoekstra et al.,2011)and the life cycle assessment (LCA)framework (ISO,2014;Pfisteret al..2009:Ridoutt Pfister.2013).With totally different quantification perspectives and units while resembledpurposes,the debates on feasibility or rationality of the two frameworks are still on,mostly with mutual criti-cisms(Hoekstra,2016;Pfister et al.,2017;Vanham Mekonnen,2021).However,the two leading scholars foreach method co-published a viewpoint and claimed that the two frameworks have different foci in assessmentsand could take advantage of the strengths of each approach (Boulay et al.,2013).However,there is still a lackof convincing evidence to demonstrate the synergy between the two approaches.For the WFN framework,whenthe blue WF in a certain areaexceeds renewable blue water,thereby violating environmental flow standards andconsuming groundwater,the area's blue WF is defined as the "unsustainable blue WF."The VW consumed andembedded in trade products under the same cases is called unsustainable virtual blue water (Hoekstra Me-konnen,2016).Within the WFN framework.Rosa et al.(2019)found that 52%of the world's irrigation water isunsustainable,15%of which is for export;Mekonen and Hoekstra (2020)reported that 57%of the global blueWF of crop production is unsustainable,of which nearly 70%is contributed by the production of wheat,rice,cotton,sugar cane,and fodder;Gao et al.(2020)found that the flow of unsustainable virtual blue water relatedto major crops between provinces in mainland China increased by 8%from 2004 to 2013.For the LCA frame-work,multiplying the blue WF with the local WS index obtains the water scarcity footprint (WSF;ISO,2014;Pfister et al.,2009;Ridoutt Pfister,2013),and the corresponding VW export is scarce weighted VW(SVW;Lenzen etal.,2013).The relative assessment tends to express the potential environmental impact caused by bluewater consumption in the unit H2O-eq.meaning that one cubic meter equivalent of WF represents the burden onfreshwater systems of one cubic meter of freshwater consumption based on the WS index.Applying the LCAframework,Wiedemann et al.(2017)observed lower WSF per kg of chicken meat produced in Queensland com-pared to South Australia.Using the same framework,Bai et al.(2018)quantified the WSF of the finishing hog ina typical large-scale intensive pig farming company in Henan Province,China,with a value of 353.67 m3 HO-eqt-1.However,to the best of our knowledge,a sustainability evaluation of the WF and VW flow of animal prod-ucts at the intra-national scale is still lacking.Moreover.studies seldom consider that their feed ingredients comefrom different water-scarce regions and tend to assume that the WS in the studied area is the same level.This willlead to the key information that the scarce water consumed locally comes from other export regions being hiddenand ignored.and the stress on regional water resources will be underestimated or overestimated.thus affectingdecision-making.This issue matters because over 90 percent of the WF of livestock comes from producing feedcrops (Mekonnen Hoekstra,2012;Xie et al.,2020).For instance,if water-rich region A imports feed crops forlivestock from water-scarce region B,then pervious WS assessments would attribute WF of the livestock to re-gion A's water endowments,which would be misleading remote water scarcities within the value chain of animalproducts.Although Lenzen et al.(2013)and Zhao et al.(2018)have examined the scarcity in VW flows at theinterational and subnational scales,respectively,the evaluation of specific animal products is lacking.To fill the abovementioned research gaps,the current study uses mainland China-the world's largest pork pro-ducer-as a study case,aims to comprehensively assess and compare the sustainability of WFs and inter-provin-cial VW flows related to pork for the years 2008 and 2017.Distinguishing between North and South China (Xieet al.,2004;Figure 1)is a widely used approach of regional delimitation in water impact assessments given itseasier reminder and comparison to the world's largest physical water transfer project the South-to-North WaterTransfer projects (e.g..Ma et al.,2006;Zhao et al.,2015;Zhuo et al.,2016).Other than its role as the largest porkproducer,China has been facing increasingly intensive inter-regional crop-related VW flows,mainly from therelatively drier north to the wetter south (Ma et al..2006:Zhuo et al..2016).The monsoon climate defines theuneven water endowments between the north and south (Piao et al.,2010),while the land distribution defines themismatch of water supply and demands for agriculture.By the year 2019,Northern Provinces accounted for 58%JI ET AL2of18