It's the full water cycle, growth of specific feed crops, feeding the animal etc.
How much water would be saved if everyone in the world became vegetarian? And how much more if everyone went vegan? A
study in Environmental Research Letters (ERL)calculates the potential water savings to be gained from a change in diet.
Animal protein consumption
Already one third of the world's population lives in areas of water scarcity. By 2050, estimates suggest that the global population will have swelled to 9.6 billion, putting further pressure on water supplies. Crops guzzle water and agriculture is responsible for around nine-tenths of global freshwater consumption. One way to make agricultural water savings might be to encourage people to adopt a different diet.
In particular, eating less meat is likely to make a big difference to water consumption, because livestock farming requires large amounts of water to produce the cereals used as animal feed. So what would happen if we all cut down on our carnivorous tendencies?
Mika Jalava and his colleagues from Aalto University, Finland, and the University of Bonn, Germany, have addressed this question by gathering data on water use and diet worldwide.
The researchers calculated how much green water (rain) and blue water (rivers, lakes and reservoirs) would be saved if everyone adopted current dietary guidelines issued by the World Health Organisation (WHO). They also modelled four potential scenarios where the amount of protein from animals in each diet is gradually reduced to 50%, 25%, 12.5% or 0% (a vegan diet).
For diets adjusted to the WHO recommendations, Jalava and the team found that energy consumption fell by 3.6%, indicating that on a global scale the current dietary energy intake is more than adequate. However, the distribution of food was far from even. For 4.3 billion people, in 102 countries, food intake decreased, while it increased for 2.3 billion people, in 74 countries.
Average global water use changed very little under the WHO diet scenario, but individual countries saw big changes. The largest increases in water use were for those nations currently suffering from undernourishment, while decreases were seen in countries around the Mediterranean, Kazakhstan and Iran.
Under the scenarios that adjusted animal protein (to 50%, 25%, 12.5% and 0% of the diet), significant changes in water consumption took place, with green water falling by 6%, 11%, 15% and 21% respectively, and blue water use falling by 4%, 6%, 9%, and 14%. Once again, the changes varied greatly by country, depending on local diet and climate. In Latin America, Europe, Central and Eastern Asia, and Sub-Saharan Africa diet change mainly reduced green water use. In the Middle East, North America, Australia and Oceania, both blue and green water footprints decreased considerably, while in South and Southeast Asia diet change did not result in decreased water use.
Partly these differences were due to climate, with many of the driest countries, which rely heavily on irrigation, seeing some of the greatest drops in water usage. However, local dietary preferences also played a role.
"The water used to produce different foodstuffs varies widely," said Jalava. "For example, the world average footprints for one kilogram of bovine meat are 7002 litres of green water and 256 litres of blue water. On the other hand, the figures for one kilogram of pig meat are 3155 litres of green and 276 litres of blue water. Thus comparing a hypothetical country with all meat in the diet originating from bovine livestock and another where only pig is used, the relation between blue and green water savings would be different." Meanwhile, reducing animal-protein content for diets in South and Southeast Asia had little impact because diets in this region are already very low in animal-based proteins.
The greatest water savings from dietary change can be achieved in the US, many Central Asian countries and in the Middle East, the results show. Looking ahead, the findings indicate that a worldwide change in diet could save enough water to feed an additional 1.8 billion people. But introducing such dietary changes might not be easy.
"Not only will people have to change their behaviour, but also trade patterns, employment and human health would all be affected by such drastic dietary change," Jalava told environmentalresearchweb. "Traditions and preferences should be understood and followed, to make the recommendations acceptable. Careful optimization won't help a bit if the result doesn't resonate with people's taste."