Diet change—a solution to reduce water use?

Abstract

Water and land resources are under increasing pressure in many parts of the globe. Diet change has been suggested as a measure to contribute to adequate food security for the growing population. This paper assesses the impact of diet change on the blue and green water footprints of food consumption. We first compare the water consumption of the current diets with that of a scenario where dietary guidelines are followed. Then, we assess these footprints by applying four scenarios in which we gradually limit the amount of protein from animal products to 50%, 25%, 12.5% and finally 0% of the total protein intake. We find that the current water use at the global scale would be sufficient to secure a recommended diet and worldwide energy intake. Reducing the animal product contribution in the diet would decrease global green water consumption by 6%, 11%, 15% and 21% within the four applied scenarios, while for blue water, the reductions would be 4%, 6%, 9% and 14%. In Latin America, Europe, Central and Eastern Asia and Sub-Saharan Africa, diet change mainly reduces green water use, while in the Middle East region, North America, Australia and Oceania, both blue and green water footprints decrease considerably. At the same time, in South and Southeast Asia, diet change does not result in decreased water use. Our results show that reducing animal products in the human diet offers the potential to save water resources, up to the amount currently required to feed 1.8 billion additional people globally; however, our results show that the adjustments should be considered on a local level.

Using Water Footprints to Identify Alternatives for Conserving Local Water Resources in California

“…The report was based on information published from about 1995 to 2010 on a range of relevant topics and was comprehensive in its scope. Nonetheless, similar input information for assessing blue water footprints is available for at least some other nations and/or regions [7]. The Pacific Institute's 2012 report did not address aquaculture's water use, and it was not considered in this paper.…”

“…First, plant-based diets generally conserve more green than blue water because the former usually represents a larger portion of the total footprint devoted to food [17]. In particular, green water usually comprises a major portion of the footprint for animal-based foods [5,7]. Second, the vegan diets presented in Figure 3 assume that people eat plant-based foods for only one-third (33%) or one-seventh (14%) of their meals, rather than for every meal.…”

“…The largest water savings for both blue and green were observed in water scarce countries of the Middle East and North Africa. Jalava et al [7] concluded that although limiting the consumption of animal products would decrease both blue and green water footprints globally, dietary shifts should be considered in combination with reducing food waste or loss on more localized scales.…”

“…A 14% decrease in global blue water consumption was estimated for eliminating all animal products from the diet, but the authors noted that the relative importance of dietary shifts to water conservation is highly dependent on the available water resources within a specific country [7]. The largest water savings for both blue and green were observed in water scarce countries of the Middle East and North Africa.…”

“…From the perspective of nutritional water productivity, which describes the mass or energy of food produced per unit volume of water, changes in food habits may be required to provide the additional water needed to feed a larger population [6]. Food security will probably depend on people consuming a higher percentage of plant-based foods that can reduce the water necessary to grow crops [7]. Regional effects of climate change on crop yields and water availability could also influence the timing and extent of required changes in dietary habits [8].…”