This small change to your diet can slash your carbon footprint in half. Here's how

Americans who eat beef could slash their diet’s carbon footprint by as much as 48% by swapping just one serving per day for a more planet-friendly alternative, according to a new study.

Using real-world data from a survey of what more than 16,000 Americans eat in an average day, researchers calculated how much of a difference people could make if they swapped one high-impact food item for similar, more sustainable options.

They examined how the change would affect two metrics - their daily diets’ greenhouse gas emissions and water scarcity footprint, a measure of the irrigated water used to produce the foods they eat that takes into account regional variations in water scarcity.

The highest impact item in Americans’ diet is beef and around 20% of survey respondents ate at least one serving of it in a day. If they collectively swapped one serving of beef - for example, choosing ground turkey instead of ground beef - their diets’ greenhouse gas emissions fell by an average of 48% and water-use impact declined by 30%.

“People can make a significant difference in their carbon footprint with very simple changes - and the easiest one would be to substitute poultry for beef,” says lead author Diego Rose, a professor of nutrition and food security at Tulane University’s School of Public Health and Tropical Medicine.

The study also examined how the change would affect the overall environmental impact of all food consumption in the US in a day - including if 80% of diets did not change at all. If only the 20% of Americans who ate beef in a day switched to something else for one meal, that would reduce the overall carbon footprint of all US diets by 9.6% and reduce water-use impacts by 5.9%.

Agricultural production accounts for about a quarter of global greenhouse gas emissions and about 70% of global freshwater withdrawals. For the study, researchers built an extensive database of the greenhouse gas emissions and water use related to the production of foods and linked it to a large federal survey that asked people what they ate over a 24-hour period.

Although swapping beef had the greatest impact, they also measured the impact of changing other items. Replacing a serving of shrimp with cod reduced greenhouse gas emissions by 34%; replacing dairy milk with soy milk resulted in an 8% reduction.

The most significant reduction in the water scarcity footprint came from replacing asparagus with peas, resulting in a 48% decrease. Substituting peanuts in place of almonds decreased the water scarcity footprint by 30%.

Although individual substitutions were the focus of the study, Rose says that addressing climate change must involve more than singular actions.

“The changes needed to address our climate problems are major. They are needed across all sectors and along all levels of human organization from international agencies to federal and state governments to communities and households,” Rose says.

“Many individuals feel strongly about this and wish to change our climate problem through direct actions that they can control. This, in turn, can change social norms about both the seriousness of the problem and the potential solutions that can address it. Our study provides evidence that even simple steps can assist in these efforts.”

The study appears in the American Journal of Clinical Nutrition. Additional co-authors are from the University of Michigan and Tulane.