Topic review

Water Footprint of Food Production

Submitted by: Mesfin M Mekonnen

Definition

Blue water footprint - the volume of fresh surface and groundwater that has been evaporated or incorporated into a product.

Green water footprint - the rainwater that is stored in the root zone of the soil and evapotranspired or incorporated into the product.

Unsustainable blue water footprint - when it exceeds the available renewable blue water, thereby violating the environmental flow standard and depleting groundwater

Water footprint - an indicator of the direct and indirect water use to produce the goods and services we use.

1. Introduction

Agriculture is by far the largest user of water. Agricultural production needs to increase by almost 50% by 2050 compared to 2012 to meet the rising demand for food, fiber, and biofuels. This is probably going to require more water. Most of the increase in agricultural production is expected to occur in Sub-Saharan Africa and South Asia, where the agricultural output will need to more than double by 2050 [1]. The expected increase in the rest of the world is around 30%. Agricultural production has increased by 260% between 1961 and 2018 [2]. During the same period, the harvested crop area increased by 47%, suggesting that 113% of the increase in production is linked to an increase in crop yield. The increase in crop yield between 1961 and 1990 was 72%, but between 1991 and 2018, the increase was 43%, indicating that yields are now rising at a slower rate than in previous decades [2]. The increase in crop yields was largely due to increased irrigation, improved crop varieties, agrochemical inputs, and improved soil and water management. However, the increase in crop productivity is not expected to continue indefinitely. In most parts of the world, yields for major crops have begun to stagnate [3,4]. Climate change, soil degradation, and salinization of irrigated areas will potentially limit future increases in production. Ray et al. [5] have shown that with the current rate of yield increase, it is not possible to meet the expected food demand by 2050. They have argued that some level of cropland expansion is needed to meet the food production deficits but at a higher environmental cost to biodiversity.

The amount of food available for human consumption is affected by the allocation of crops to other nonfood uses such as animal feed, bioenergy, and industrial uses. Globally, only 67% of the crop produced (by mass) or 55% of the calories produced is available for direct human consumption [6]. The remaining crop was allocated to animal feed (24% by mass) and other industrial use, including bioenergy (9% by weight). Animal production is less efficient than crop production in converting feed to human edible food [7,8,9,10]. As a result, only 12% of the 36% of the global calories used for animal feed will ultimately contribute to human diets [6].

In 2011, the global water footprint (WF) of agricultural production was 8362 km3/year (80% green, 11% blue, and 9% grey) [11]. World water demand is expected to increase by 20%–30% between 2010 and 2050 [12]. Demand for land and water resources has increased significantly, and these resources are expected to be scarcer in the future. Efficient water management in agriculture is needed to meet the growing demand for food and reduce poverty and hunger in a sustainable manner. The question is how the world will feed the global population without further impacting the freshwater and ecosystems. Several researchers have advocated for sustainable intensification [10,13,14,15,16], dietary changes, and reduction of food waste and loss [17,18,19] to feed the world. A number of studies have shown the value of virtual water trade in global water saving, reducing water scarcity, and it will help to reduce the risk of water scarcity [20,21,22,23]. This paper provides a brief review of the WF of food production, the water demand for different food products and diets, and the WF of food loss and waste. 

2. From Quantification to Sustainability Assessment

Over the last few years, the assessment of WFs of national consumption and production has shown significant improvement in terms of product coverage, spatial and temporal detail, and sustainability assessment [57]. Hoekstra and Hung [33] were the first to estimate the WF of national consumption of 38 crops for a large number of countries. The second global assessment made a number of improvements in terms of product coverage by including all crops and livestock products and other refinements [32,36]. The third global study made further refinements by assessing the national water footprints of production and consumption at a high spatial and temporal resolution [11,58]. In addition to the global studies on the WF of crop production mentioned earlier [24,25,26,27,28,29,59], other national [60,61,62,63,64], regional or basin [65,66], and global studies [28,67] have also traced and mapped the WF of consumption per country, but none of these studies assessed the sustainability of the blue WF of consumption at the place of production. The blue WF is unsustainable if it is above the available renewable blue water and violates the environmental flow requirements.

Van Oel et al. [68] carried out the first assessment of the sustainability of the WF in relation to Dutch consumption. In a case study for France, Ercin et al. [69] assessed the sustainability of the WF of consumption of France, identifying priority basins and products. Hoekstra and Mekonnen [70] assessed the sustainability and water-use efficiency of the UK’s WF of consumption. There are more recent works that have assessed the unsustainable blue WF of consumption for a single country or EU as a whole [71,72]. A few studies have assessed the sustainability of the WF of crop production and virtual water flows at a global level [73,74,75]. Other studies focused on sustainability of groundwater use [76,77,78,79,80].

In a more detailed global study, Mekonnen and Hoekstra [81] estimated that 513 km3/year, or 57% of the blue WF, related to crop production, was unsustainable. Approximately 75% of the global unsustainable blue WF is related to the production of only six crops (Figure 3a). These are wheat, rice, cotton, sugar cane, fodder, and maize. Five countries account for about 70% of the unsustainable blue WF (Figure 3b), India, China, the US, Pakistan, and Iran. Of the total unsustainable blue WF, 90% was for food and fodder crops, while only 10% was for fiber crops, rubber, and tobacco. Figure 4 shows the sustainable and unsustainable blue WF for global cereal production. The unsustainable portion of the blue WF is large in the Indus and Ganges river basins in India and Pakistan, in the north-eastern part of China, and in the US. High Plains aquifer. The study also showed that some 25% of global blue water can be saved by reducing the WF of each crop to the benchmark level.

Figure 3. The unsustainable blue WF related to crop production: (a) Contribution of different crops toward the global blue unsustainable blue WF of crop production; (b) location of the unsustainable blue WF of crop production. Data source from Mekonnen and Hoekstra [81].

Figure 4. The sustainable (green) and unsustainable (yellow to dark red) parts of the blue WF of global cereals production. Data source from Mekonnen and Hoekstra [81].

Reference

  1. The Future of Food and Agriculture-Trends and Challenges; Food and Agriculture Organization: Rome, Italy, 2017. [Google Scholar]
  2. FAOSTAT Online Database; FAO: Rome, Italy, 2020. [Google Scholar]
  3. Grassini, P.; Eskridge, K.M.; Cassman, K.G. Distinguishing between yield advances and yield plateaus in historical crop production trends. Nat. Commun. 2013, 4. [Google Scholar] [CrossRef] [PubMed]
  4. Ray, D.K.; Ramankutty, N.; Mueller, N.D.; West, P.C.; Foley, J.A. Recent patterns of crop yield growth and stagnation. Nat. Commun. 2012, 3, 1293. Available online: http://www.nature.com/ncomms/journal/v3/n12/suppinfo/ncomms2296_S1.html (accessed on 13 April 2015). [CrossRef] [PubMed]
  5. Ray, D.K.; Mueller, N.D.; West, P.C.; Foley, J.A. Yield trends are insufficient to double global crop production by 2050. PLoS ONE 2013, 8, e66428. [Google Scholar] [CrossRef] [PubMed]
  6. Cassidy, E.S.; West, P.C.; Gerber, J.S.; Foley, J.A. Redefining agricultural yields: From tonnes to people nourished per hectare. Environ. Res. Lett. 2013, 8, 034015. [Google Scholar] [CrossRef]
  7. Mekonnen, M.M.; Neale, C.M.U.; Ray, C.; Erickson, G.E.; Hoekstra, A.Y. Water productivity in meat and milk production in the USA from 1960 to 2016. Environ. Int. 2019, 132, 105084. [Google Scholar] [CrossRef]
  8. Wirsenius, S. Efficiencies and biomass appropriation of food commodities on global and regional levels. Agric. Syst. 2003, 77, 219–255. [Google Scholar] [CrossRef]
  9. Bouwman, A.F.; Van der Hoek, K.W.; Eickhout, B.; Soenario, I. Exploring changes in world ruminant production systems. Agric. Syst. 2005, 84, 121–153. [Google Scholar] [CrossRef]
  10. Tilman, D.; Balzer, C.; Hill, J.; Befort, B.L. Global food demand and the sustainable intensification of agriculture. Proc. Natl. Acad. Sci. USA 2011, 108, 20260–20264. [Google Scholar] [CrossRef]
  11. Hoekstra, A.Y.; Mekonnen, M.M. The water footprint of humanity. Proc. Natl. Acad. Sci. USA 2012, 109, 3232–3237. [Google Scholar] [CrossRef]
  12. Burek, P.; Satoh, Y.; Fischer, G.; Kahil, M.T.; Scherzer, A.; Tramberend, S.; Nava, L.F.; Wada, Y.; Eisner, S.; Flörke, M.; et al. Water Futures and Solution-Fast Track Initiative (Final Report); IIASA: Laxenburg, Austria, 2016. [Google Scholar]
  13. Cassman, K.G.; Grassini, P. A global perspective on sustainable intensification research. Nat. Sustain. 2020, 3, 262–268. [Google Scholar] [CrossRef]
  14. Drechsel, P.; Heffer, P.; Magen, H.; Mikkelsen, R.; Wichelns, D. Managing Water and Fertilizer for Sustainable Agricultural Intensification; International Fertilizer Industry Association (IFA): Paris, France; International Water Management Institute (IWMI): Colombo, Sri Lanka; International Plant Nutrition Institute (IPNI): Peachtree Corners, GA, USA; International Potash Institute (IPI): Horgen, Switzerland, 2015. [Google Scholar]
  15. Garnett, T.; Appleby, M.C.; Balmford, A.; Bateman, I.J.; Benton, T.G.; Bloomer, P.; Burlingame, B.; Dawkins, M.; Dolan, L.; Fraser, D.; et al. Sustainable intensification in agriculture: Premises and policies. Science 2013, 341, 33–34. [Google Scholar] [CrossRef] [PubMed]
  16. Godfray, H.C.J.; Beddington, J.R.; Crute, I.R.; Haddad, L.; Lawrence, D.; Muir, J.F.; Pretty, J.; Robinson, S.; Thomas, S.M.; Toulmin, C. Food security: The challenge of feeding 9 billion people. Science 2010, 327, 812–818. [Google Scholar] [CrossRef] [PubMed]
  17. Foley, J.A.; Ramankutty, N.; Brauman, K.A.; Cassidy, E.S.; Gerber, J.S.; Johnston, M.; Mueller, N.D.; O’Connell, C.; Ray, D.K.; West, P.C.; et al. Solutions for a cultivated planet. Nature 2011, 478, 337–342. [Google Scholar] [CrossRef]
  18. Jalava, M.; Guillaume, J.H.A.; Kummu, M.; Porkka, M.; Siebert, S.; Varis, O. Diet change and food loss reduction: What is their combined impact on global water use and scarcity? Earth’s Future 2016, 4, 62–78. [Google Scholar] [CrossRef]
  19. Kummu, M.; de Moel, H.; Porkka, M.; Siebert, S.; Varis, O.; Ward, P.J. Lost food, wasted resources: Global food supply chain losses and their impacts on freshwater, cropland, and fertiliser use. Sci. Total Environ. 2012, 438, 477–489. [Google Scholar] [CrossRef] [PubMed]
  20. Liu, W.; Yang, H.; Liu, Y.; Kummu, M.; Hoekstra, A.Y.; Liu, J.; Schulin, R. Water resources conservation and nitrogen pollution reduction under global food trade and agricultural intensification. Sci. Total Environ. 2018, 633, 1591–1601. [Google Scholar] [CrossRef]
  21. Liu, W.; Antonelli, M.; Kummu, M.; Zhao, X.; Wu, P.; Liu, J.; Zhuo, L.; Yang, H. Savings and losses of global water resources in food-related virtual water trade. WIREs Water 2019, 6, e1320. [Google Scholar] [CrossRef]
  22. Mekonnen, M.M.; Hoekstra, A.Y. A global and high-resolution assessment of the green, blue and grey water footprint of wheat. Hydrol. Earth Syst. Sci. 2010, 14, 1259–1276. [Google Scholar] [CrossRef]
  23. Chapagain, A.K.; Hoekstra, A.Y.; Savenije, H.H.G. Water saving through international trade of agricultural products. HESS 2006, 10, 455–468. [Google Scholar] [CrossRef]
  24. Siebert, S.; Döll, P. Quantifying blue and green virtual water contents in global crop production as well as potential production losses without irrigation. J. Hydrol. 2010, 384, 198–217. [Google Scholar] [CrossRef]
  25. Liu, J.; Yang, H. Spatially explicit assessment of global consumptive water uses in cropland: Green and blue water. J. Hydrol. 2010, 384, 187–197. [Google Scholar] [CrossRef]
  26. Liu, J.; Zehnder, A.J.B.; Yang, H. Global consumptive water use for crop production: The importance of green water and virtual water. Water Resour. Res. 2009, 45. [Google Scholar] [CrossRef]
  27. Hanasaki, N.; Inuzuka, T.; Kanae, S.; Oki, T. An estimation of global virtual water flow and sources of water withdrawal for major crops and livestock products using a global hydrological model. J. Hydrol. 2010, 384, 232–244. [Google Scholar] [CrossRef]
  28. Fader, M.; Gerten, D.; Thammer, M.; Heinke, J.; Lotze-Campen, H.; Lucht, W.; Cramer, W. Internal and external green-blue agricultural water footprints of nations, and related water and land savings through trade. Hydrol. Earth Syst. Sci. 2011, 15, 1641–1660. [Google Scholar] [CrossRef]
  29. Mekonnen, M.M.; Hoekstra, A.Y. The green, blue and grey water footprint of crops and derived crop products. HESS 2011, 15, 1577–1600. [Google Scholar] [CrossRef]
  30. Rost, S.; Gerten, D.; Bondeau, A.; Lucht, W.; Rohwer, J.; Schaphoff, S. Agricultural green and blue water consumption and its influence on the global water system. Water Resour. Res. 2008, 44. [Google Scholar] [CrossRef]
  31. Huang, Z.; Hejazi, M.; Tang, Q.; Vernon, C.R.; Liu, Y.; Chen, M.; Calvin, K. Global agricultural green and blue water consumption under future climate and land use changes. J. Hydrol. 2019, 574, 242–256. [Google Scholar] [CrossRef]
  32. Hoekstra, A.Y.; Chapagain, A.K. Globalization of Water: Sharing the Planet’s Freshwater Resources; Blackwell: Oxford, UK, 2008. [Google Scholar]
  33. Hoekstra, A.Y.; Hung, P.Q. Virtual Water Trade: A Quantification of Virtual Water Flows between Nations in Relation to International Crop Trade, 11th ed.; IHE: Delft, The Netherlands, 2002. [Google Scholar]
  34. Chapagain, A.K.; Hoekstra, A.Y. Water Footprints of Nations, 16th ed.; UNESCO-IHE: Delft, The Netherlands, 2004. [Google Scholar]
  35. Chapagain, A.K.; Hoekstra, A.Y. Virtual Water Flows between Nations in Relation to Trade in Livestock and Livestock Products; Value of Water Research Report Series No. 13; UNESCO-IHE: Delft, The Netherlands, 2003. [Google Scholar]
  36. Hoekstra, A.Y.; Chapagain, A.K. Water footprints of nations: Water use by people as a function of their consumption pattern. Water Resour. Manage. 2007, 21, 35–48. [Google Scholar] [CrossRef]
  37. Mekonnen, M.; Hoekstra, A. A global assessment of the water footprint of farm animal products. Ecosystems 2012, 15, 401–415. [Google Scholar] [CrossRef]
  38. Gerbens-Leenes, P.W.; Mekonnen, M.M.; Hoekstra, A.Y. The water footprint of poultry, pork and beef: A comparative study in different countries and production systems. Water Resour. Ind. 2013, 1–2, 25–36. [Google Scholar] [CrossRef]
  39. Pahlow, M.; van Oel, P.R.; Mekonnen, M.M.; Hoekstra, A.Y. Increasing pressure on freshwater resources due to terrestrial feed ingredients for aquaculture production. Sci. Total Environ. 2015, 536, 847–857. [Google Scholar] [CrossRef] [PubMed]
  40. Tilman, D.; Clark, M. Global diets link environmental sustainability and human health. Nature 2014, 515, 518–522. [Google Scholar] [CrossRef] [PubMed]
  41. FAO; WHO. Sustainable Healthy Diets-Guiding Principles; Food and Agriculture Organization (FAO); World Health Organization (WHO): Rome, Italy, 2019. [Google Scholar]
  42. Hoekstra, A.Y. The hidden water resource use behind meat and dairy. Anim. Front. 2012, 2, 3–8. [Google Scholar] [CrossRef]
  43. Hoekstra, A.Y. The water footprint of animal products. In The Meat Crisis: Developing More Sustainable Production and Consumption; D’Silva, J., Webster, J., Eds.; Earthscan: London, UK, 2010; pp. 22–33. [Google Scholar]
  44. Springmann, M.; Clark, M.; Mason-D’Croz, D.; Wiebe, K.; Bodirsky, B.L.; Lassaletta, L.; de Vries, W.; Vermeulen, S.J.; Herrero, M.; Carlson, K.M.; et al. Options for keeping the food system within environmental limits. Nature 2018, 562, 519–525. [Google Scholar] [CrossRef] [PubMed]
  45. Willett, W.; Rockström, J.; Loken, B.; Springmann, M.; Lang, T.; Vermeulen, S.; Garnett, T.; Tilman, D.; DeClerck, F.; Wood, A.; et al. Food in the anthropocene: The EAT-lancet commission on healthy diets from sustainable food systems. Lancet 2019, 393, 447–492. [Google Scholar] [CrossRef]
  46. Kim, B.F.; Santo, R.E.; Scatterday, A.P.; Fry, J.P.; Synk, C.M.; Cebron, S.R.; Mekonnen, M.M.; Hoekstra, A.Y.; de Pee, S.; Bloem, M.W.; et al. Country-specific dietary shifts to mitigate climate and water crises. Glob. Environ. Chang. 2020, 62, 101926. [Google Scholar] [CrossRef]
  47. Vanham, D.; Mekonnen, M.M.; Hoekstra, A.Y. The water footprint of the EU for different diets. Ecol. Indic. 2013, 32, 1–8. [Google Scholar] [CrossRef]
  48. Vanham, D.; Hoekstra, A.Y.; Bidoglio, G. Potential water saving through changes in European diets. Environ. Int. 2013, 61, 45–56. [Google Scholar] [CrossRef]
  49. Jalava, M.; Kummu, M.; Porkka, M.; Siebert, S.; Varis, O. Diet change-a solution to reduce water use? Environ. Res. Lett. 2014, 9, 074016. [Google Scholar] [CrossRef]
  50. Mekonnen, M.M.; Fulton, J. The effect of diet changes and food loss reduction in reducing the water footprint of an average American. Water Int. 2018, 43, 860–870. [Google Scholar] [CrossRef]
  51. Tom, M.S.; Fischbeck, P.S.; Hendrickson, C.T. Energy use, blue water footprint, and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the USA. Environ. Syst. Decis. 2016, 36, 92–103. [Google Scholar] [CrossRef]
  52. Harris, F.; Moss, C.; Joy, E.J.M.; Quinn, R.; Scheelbeek, P.F.D.; Dangour, A.D.; Green, R. The water footprint of diets: A global systematic review and meta-analysis. Adv. Nutr. 2019, 11, 375–386. [Google Scholar] [CrossRef] [PubMed]
  53. The State of Food and Agriculture 2019. Moving Forward on Food Loss and Waste Reduction; Food and Agriculture Organization (FAO): Rome, Italy, 2019. [Google Scholar]
  54. Liu, J.; Lundqvist, J.; Weinberg, J.; Gustafsson, J. Food losses and waste in china and their implication for water and land. Environ. Sci. Technol. 2013, 47, 10137–10144. [Google Scholar] [CrossRef] [PubMed]
  55. Searchinger, T.; Waite, R.; Hanson, C.; Ranganathan, J. Creating a Sustainable Food Future’ Shows that It is Possible-But There is no Silver Bullet; World Resources Institute: Washington, DC, USA, 2019. [Google Scholar]
  56. Global Food Losses and Food Waste-Extent, Causes and Prevention; Food and Agriculture Organization (FAO): Rome, Italy, 2011. [Google Scholar]
  57. Hoekstra, A.Y. Water footprint assessment: Evolvement of a new research field. Water Resour. Manage. 2017, 31, 3061–3081. [Google Scholar] [CrossRef]
  58. Mekonnen, M.M.; Hoekstra, A.Y. National Water Footprint Accounts: The Green, Blue and Grey Water Footprint of Production and Consumption; UNESCO-IHE: Delft, The Netherlands, 2011. [Google Scholar]
  59. Rost, S.; Gerten, D.; Heyder, U. Human alterations of the terrestrial water cycle through land management. Adv. Geosci. 2008, 18, 43–50. [Google Scholar] [CrossRef]
  60. Mekonnen, M.M.; Hoekstra, A.Y. Water conservation through trade: The case of Kenya. Water Int. 2014, 39, 1–18. [Google Scholar] [CrossRef]
  61. Zhuo, L.; Mekonnen, M.M.; Hoekstra, A.Y. Consumptive water footprint and virtual water trade scenarios for China — With a focus on crop production, consumption and trade. Environ. Int. 2016, 94, 211–223. [Google Scholar] [CrossRef]
  62. Bulsink, F.; Hoekstra, A.Y.; Booij, M.J. The water footprint of Indonesian provinces related to the consumption of crop products. HESS 2010, 14, 119–128. [Google Scholar] [CrossRef]
  63. Marston, L.; Ao, Y.; Konar, M.; Mekonnen, M.M.; Hoekstra, A.Y. High-resolution water footprints of production of the united states. Water Resour. Res. 2018, 54, 2288–2316. [Google Scholar] [CrossRef]
  64. Schyns, J.; Hamaideh, A.; Hoekstra, A.; Mekonnen, M.; Schyns, M. Mitigating the risk of extreme water scarcity and dependency: The case of jordan. Water 2015, 7, 5705–5730. [Google Scholar] [CrossRef]
  65. Mekonnen, M.; Pahlow, M.; Aldaya, M.; Zarate, E.; Hoekstra, A. Sustainability, efficiency and equitability of water consumption and pollution in latin America and the caribbean. Sustainability 2015, 7, 2086–2112. [Google Scholar] [CrossRef]
  66. Zeitoun, M.; Allan, J.A.; Mohieldeen, Y. Virtual water ‘flows’ of the nile basin, 1998–2004: A first approximation and implications for water security. Glob. Environ. Change 2010, 20, 229–242. [Google Scholar] [CrossRef]
  67. Chen, Z.-M.; Chen, G.Q. Virtual water accounting for the globalized world economy: National water footprint and international virtual water trade. Ecol. Indicators 2013, 28, 142–149. [Google Scholar] [CrossRef]
  68. Van Oel, P.R.; Mekonnen, M.M.; Hoekstra, A.Y. The external water footprint of The Netherlands: Geographically-explicit quantification and impact assessment. Ecolog. Econ. 2009, 69, 82–92. [Google Scholar] [CrossRef]
  69. Ercin, A.E.; Mekonnen, M.M.; Hoekstra, A.Y. Sustainability of national consumption from a water resources perspective: The case study for France. Ecolog. Econ. 2013, 88, 133–147. [Google Scholar] [CrossRef]
  70. Hoekstra, A.Y.; Mekonnen, M.M. Imported water risk: The case of the UK. Environ. Res. Lett. 2016, 11, 055002. [Google Scholar] [CrossRef]
  71. Dolganova, I.; Mikosch, N.; Berger, M.; Núñez, M.; Müller-Frank, A.; Finkbeiner, M. The water footprint of European agricultural imports: Hotspots in the context of water scarcity. Resources 2019, 8, 141. [Google Scholar] [CrossRef]
  72. Finogenova, N.; Dolganova, I.; Berger, M.; Núñez, M.; Blizniukova, D.; Müller-Frank, A.; Finkbeiner, M. Water footprint of German agricultural imports: Local impacts due to global trade flows in a fifteen-year perspective. Sci. Total Environ. 2019, 662, 521–529. [Google Scholar] [CrossRef]
  73. Wang, R.; Zimmerman, J. Hybrid analysis of blue water consumption and water scarcity implications at the global, national, and basin levels in an increasingly globalized world. Environ. Sci. Technol. 2016, 50, 5143–5153. [Google Scholar] [CrossRef]
  74. Jägermeyr, J.; Pastor, A.; Biemans, H.; Gerten, D. Reconciling irrigated food production with environmental flows for sustainable development goals implementation. Nat. Commun. 2017, 8, 15900. [Google Scholar] [CrossRef]
  75. Rosa, L.; Chiarelli, D.D.; Tu, C.; Rulli, M.C.; D’Odorico, P. Global unsustainable virtual water flows in agricultural trade. Environ. Res. Lett. 2019, 14, 114001. [Google Scholar] [CrossRef]
  76. Dalin, C.; Taniguchi, M.; Green, T.R. Unsustainable groundwater use for global food production and related international trade. Glob. Sustain. 2019, 2, e12. [Google Scholar] [CrossRef]
  77. Dalin, C.; Wada, Y.; Kastner, T.; Puma, M.J. Groundwater depletion embedded in international food trade. Nature 2017, 543, 700. [Google Scholar] [CrossRef] [PubMed]
  78. Wada, Y.; van Beek, L.P.H.; Bierkens, M.F.P. Nonsustainable groundwater sustaining irrigation: A global assessment. Water Resour. Res. 2012, 48, W00L06. [Google Scholar] [CrossRef]
  79. Scanlon, B.R.; Faunt, C.C.; Longuevergne, L.; Reedy, R.C.; Alley, W.M.; McGuire, V.L.; McMahon, P.B. Groundwater depletion and sustainability of irrigation in the USA high plains and central valley. Proc. Natl. Acad. Sci. USA 2012, 109, 9320–9325. [Google Scholar] [CrossRef]
  80. Marston, L.; Konar, M.; Cai, X.; Troy, T.J. Virtual groundwater transfers from overexploited aquifers in the United States. Proc. Natl. Acad. Sci. USA 2015, 112, 8561–8566. [Google Scholar] [CrossRef]
  81. Mekonnen, M.M.; Hoekstra, A.Y. Sustainability of the blue water footprint of crops. Arizona department Water Resour. 2020, 143, 103679. [Google Scholar] [CrossRef]
  82. Mekonnen, M.M.; Hoekstra, A.Y. Four billion people facing severe water scarcity. Sci. Adv. 2016, 2. [Google Scholar] [CrossRef]
  83. Vörösmarty, C.J.; McIntyre, P.B.; Gessner, M.O.; Dudgeon, D.; Prusevich, A.; Green, P.; Glidden, S.; Bunn, S.E.; Sullivan, C.A.; Liermann, C.R.; et al. Global threats to human water security and river biodiversity. Nature 2010, 467, 555–561. [Google Scholar] [CrossRef]
  84. Hoekstra, A.Y. The Water Footprint of Modern Consumer Society; Routledge: London, UK, 2013. [Google Scholar]
  85. Hogeboom, R.J.; de Bruin, D.; Schyns, J.F.; Krol, M.S.; Hoekstra, A.Y. Capping human water footprints in the world’s river basins. Earth’s Future 2020, 8, e2019EF001363. [Google Scholar] [CrossRef]
  86. Zhuo, L.; Hoekstra, A.Y.; Wu, P.; Zhao, X. Monthly blue water footprint caps in a river basin to achieve sustainable water consumption: The role of reservoirs. Sci. Total Environ. 2019, 650, 891–899. [Google Scholar] [CrossRef] [PubMed]
  87. Mekonnen, M.M.; Hoekstra, A.Y. Water footprint benchmarks for crop production: A first global assessment. Ecol. Indic. 2014, 46, 214–223. [Google Scholar] [CrossRef]
  88. Zhuo, L.; Mekonnen, M.M.; Hoekstra, A.Y. Benchmark levels for the consumptive water footprint of crop production for different environmental conditions: A case study for winter wheat in China. Hydrol. Earth Syst. Sci. 2016, 20, 4547–4559. [Google Scholar] [CrossRef]
  89. Chukalla, A.D.; Krol, M.S.; Hoekstra, A.Y. Green and blue water footprint reduction in irrigated agriculture: Effect of irrigation techniques, irrigation strategies and mulching. Hydrol. Earth Syst. Sci. 2015, 19, 4877–4891. [Google Scholar] [CrossRef]
  90. Mekonnen, M.M.; Hoekstra, A.Y.; Neale, C.M.U.; Ray, C.; Yang, H.S. Water productivity benchmarks: The case of maize and soybean in Nebraska. Agric. Water Manage. 2020, 234, 106122. [Google Scholar] [CrossRef]
  91. Hoekstra, A.Y. Sustainable, efficient, and equitable water use: The three pillars under wise freshwater allocation. Wiley Interdiscip. Rev. Water 2014, 1, 31–40. [Google Scholar] [CrossRef]
  92. West, P.C.; Gerber, J.S.; Engstrom, P.M.; Mueller, N.D.; Brauman, K.A.; Carlson, K.M.; Cassidy, E.S.; Johnston, M.; MacDonald, G.K.; Ray, D.K.; et al. Leverage points for improving global food security and the environment. Science 2014, 345, 325–328. [Google Scholar] [CrossRef]
  93. Lowe, B.H.; Oglethorpe, D.R.; Choudhary, S. Marrying unmarried literatures: The water footprint and environmental (economic) valuation. Water 2018, 10, 1815. [Google Scholar] [CrossRef]
  94. Cazcarro, I.; Bielsa, J. Blind spots in water management, and how natural sciences could be much more relevant. Front. Plant Sci. 2020, 10.

The article is from 10.3390/w12102696

Keywords

sustainable diet, food waste, food production