A new “water scarcity footprint” measures the water-use impacts of various United States diets.

Meat consumption is the top contributor to the water scarcity footprint of the average US diet, accounting for 31% of the impacts, according to the study in Nature Food. And within the meat category, beef’s contribution is about six times higher than that of chicken.

But other foods that require lots of water or that are mainly grown in US regions where water is scarce—including certain fruits, nuts, and vegetables—also have high water-scarcity footprints, the researchers say.

“Beef is the largest dietary contributor to the water scarcity footprint, as it is for the carbon footprint,” says study lead author Martin Heller of the Center for Sustainable Systems at University of Michigan’s School for Environment and Sustainability.

“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 new approach combines the types and quantities of foods in the diets of individuals, the irrigation water required to produce those foods, and the relative scarcity of water where the irrigation occurs.

The study also includes examples of dietary substitutions that consumers can make to reduce their personal water scarcity footprint. For example, they can:

  • Replace some high water-intensity tree nuts (almonds, walnuts, and cashews) with peanuts or seeds.
  • Limit consumption of high water-intensity vegetables and replace them with lower-intensity vegetables such as fresh peas, Brussels sprouts, cabbage, and kale.
  • Replace some beef with other protein sources, such as chicken, pork, soybeans, dry edible beans, peanuts, or sunflower seeds.
  • The concept of the water scarcity footprint is akin to the more familiar carbon footprint, which estimates the greenhouse gas emissions that specific human activities, products, and processes produce. One key difference: Greenhouse gas emissions boost levels of heat-trapping gases globally, while the effects of dietary choices on water scarcity are mainly local.

Read the full article about water scarcity footprint by Jim Erickson at Futurity.