According to the new study, reducing use of animal products can have a considerable impact on areas suffering scarce water resources, as meat production requires more water than other agricultural products.
This dietary change, together with other actions such as reductions of food losses and waste, could also tackle the future challenges of food security, says lead author Mika Jalava from Aalto University in Finland.
"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," said Jalava and colleagues, writing in Environmental Research Letters.
The study is the first global-scale analysis with a focus on changes in national diets and their impact on the blue and green water use of food consumption.
Water and food security
Growth in global populations coupled with the impacts of climate change are likely to increase the pressure on already limited water resources, and could add an additional 2 billion mouths to feed by 2050. Much research has been devoted to tackling the impending crisis in food and water security, and dietary change have been suggested as one of the measures that can contribute to improving resource security in the future.
As a result, Jalava and his team assessed the impact of diet change on global water resources over four scenarios: "This study attempts to deepen the understanding of the impact of diets on resource use by analysing the effect of changes in diets on consumptive water use at a country level and at a global extent."
First, the team analysed the impact of modifying diets to fulfil the dietary guidelines by the World Health Organization (WHO), and then the effect of shifting from animal-based food products, especially meat, toward a more plant-based diet.
"In both analyses, we kept the diet composition as close to original as possible to retain the traditional and culturally acceptable food composition in each country," said the team.
Key findings
By reducing the intake of animal-based products in the diet, global green water (rainwater) consumption was projected to decrease by up to 21 %, while for blue water (irrigation water) the reductions could be up to 14 %, said the researchers.
They suggested that by shifting to vegetarian diet the world could secure adequate food supply for an additional 1.8 billion people without increasing the use of water resources.
These potential savings are, however, distributed unevenly, and even more important, their potential alleviation on water scarcity varies widely from country to country, said the team.
Regional differences
"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," wrote the team. "At the same time, in South and Southeast Asia, diet change does not result in decreased water use."
In Finland, for example, turning into a meat free diet would decrease the daily green water use of a Finn by over 530 litres but at the same time would result in nearly 50 litres increase in blue water use.
Source: Environmental Research Letters
Published online, Open Access, doi: 10.1088/1748-9326/9/7/074016
" Diet change—a solution to reduce water use?"
Authors: M Jalava, M Kummu, M Porkka, S Siebert, O Varis