(CN) — The American diet is supported by a food supply chain leaving behind a massive carbon footprint, and meat heavy diets in particular leave an outsized mark. A new study released Thursday shows the food on people’s plates is also depleting water supplies.
As more Americans and U.S. restaurants adopt plant-based menus, much attention is given to the greenhouse gases spewed into the atmosphere by the supply chain supporting meat-based diets.
But less is known about the impact on water, which can become scarce mainly at the local level whereas greenhouse gases impact global climate.
U.S.-based researchers from the University of Michigan and Tulane University tackled that question, examining the water scarcity footprints — akin to a carbon footprint, which measures greenhouse gas output — of 160 popular crops in the domestic supply chain and their impacts on watershed levels.
“Our approach is novel in that it links individual dietary choices with the water scarcity-weighted impact of irrigation for specific crops at the watershed level, thus offering insight into the distribution of impacts across a population," said coauthor Greg Keoleian with the University of Michigan’s Center for Sustainable Systems, in a statement.
At least 81% of U.S. water supplies are used in 17 Western states, according to the study.
Researchers analyzed the individual dietary choices of more than 16,800 Americans and considered the impact of water scarcity on specific regions.
“The impacts on both human and ecosystem users of another user’s freshwater consumption depend on the relative availability of water in a given region,” the study said. “For example, growing tomatoes in a drought-prone area such as California would have a very different impact on other local water users than growing them in a water-surplus area such as Louisiana.”
Data on Americans’ dietary choices was sourced from the National Health and Nutrition Examination Survey.
Meat-based diets account for the largest negative mark on water supplies, making up 31% of the negative impact from the supply chain, according to the study published Thursday in the journal Nature Food.
Lead author Martin Heller of UM’s Center for Sustainable Systems said in the statement beef had the largest impact among meat groups but researchers also considered the impact of water-needy vegetables, fruits and nuts.
"Beef is the largest dietary contributor to the water scarcity footprint, as it is for the carbon footprint," Heller said. "But the dominance of animal-based food is diminished somewhat in the water scarcity footprint, in part because the production of feed grains for animals is distributed throughout less water-scarce regions, whereas the production of vegetables, fruits and nuts is concentrated in water-scarce regions of the United States, namely the West Coast states and the arid Southwest."
The study found beef’s contribution to water scarcity was six times higher than chicken.
Study coauthor Diego Rose of Tulane University said in the statement water scarcity footprints should be key factors in dietary decisions.
"The water-use impacts of food production should be a key consideration of sustainable diets. But until now, little has been known about the water scarcity demands of diets --- especially the diets of individuals," Rose said. "There is a lot of variation in the way people eat, so having a picture with this sort of granularity — at the individual level — enables a more nuanced understanding of potential policies and educational campaigns to promote sustainable diets."
Researchers provide suggestions on how Americans can reduce their water scarcity footprints, such as by replacing water-needy almonds and cashews with more water efficient seeds or peanuts.
You can also include more Brussels sprouts, cabbage and kale in your diet, all of which require less water to grow.
Meat eaters can also seek out new protein sources such as chicken, pork, soybeans and peanuts.
Heller said conversations about domestic food production should include data on carbon output and how much water is used to produce certain crops.
"For water, part of that cost depends on the scarcity of the water where a food is grown," Heller said. "Budgeting the water scarcity footprint of our diet doesn't mean we need to eliminate the 'costly' foods completely, but it probably means we need to consume them sparingly."
Researchers did not immediately respond to a request for further comment on the study.
Subscribe to Closing Arguments
Sign up for new weekly newsletter Closing Arguments to get the latest about ongoing trials, major litigation and hot cases and rulings in courthouses around the U.S. and the world.
