The biggest eaters of burgers, steaks and ribs contribute the largest hunk of diet-related greenhouse gas emissions in the United States, according to a new study that examined individual eating habits across the country.
New research from the University of Michigan and Tulane University finds that 20 percent of American eaters accounted for nearly half of total diet-related emissions, and that their diets were heavy on beef.
If those people consumed fewer calories and shifted to a more moderate diet with less beef, that could achieve almost 10 percent of the emissions reductions needed for the U.S. to meet its targets under the Paris climate agreement, the researchers found.
The study, published Tuesday in Environmental Research Letters, adds to a growing pile of evidence linking beef with high greenhouse gas emissions, but it is the first to look at what people ate—or recalled eating—rather than at data from the U.S. Department of Agriculture, which measures how commodities flow through the economy.
"USDA tracks how much of a commodity is imported and exported, what gets used for non-food purposes, and applies food waste losses to those numbers. What comes out of that is divided by the population," said Martin Heller, the study's lead author. "What we looked at is what an individual said they ate on a particular day."
With the "recall survey" approach, Heller and his co-authors were able to examine what and how certain portions of the population ate, providing data they believe could be more useful in developing diet-related recommendations that might drive consumers toward more sustainable food choices.
The study comes as more countries are recommending lowering beef consumption for environmental reasons, and as some contemplate taxes on beef, in part to help reach their emissions targets under the 2015 Paris Agreement.
Comparing Diets, Low-Impact to Beefy
To develop their estimates, Heller and his team built a database that looked at the environmental impacts of producing 300 commonly eaten foods. They then linked the database to the National Health and Nutrition Examination Survey (NHANES), a nationally representative survey that includes self-reported dietary data for more than 16,000 Americans.
The researchers were able to rank those diets by their greenhouse gas emissions. They found that the top 20 percent, with the highest carbon footprint, was responsible for eight times more emissions than the lowest 20 percent, and that beef consumption accounted for 72 percent of the difference.
Meat production overall—largely from beef, but also including pork and chicken—accounted for 70 percent of the greenhouse gas emissions in the highest-impact group, but only 27 percent in the lowest-impact group. And while the highest-impact group consumed an average of nearly 3,000 calories a day and the lowest just above 1,300, when the researchers adjusted the findings based on caloric intake, the highest-impact group still represented five times more emissions.
The researchers did not look specifically at how the beef was produced, which can influence its carbon footprint. "That information is not available on the dietary side," Heller said. "People aren't saying where their beef is coming from or how it was raised. It was just beef."
Where Do Those Emissions Come From?
Agriculture accounts for about 9 percent of U.S. greenhouse gas emissions, according to the USDA and Environmental Protection Agency. Globally, food production is responsible for 30 percent of total emissions.
Of the 14.5 percent of global emissions from the livestock industry, more than two-thirds come from beef, largely from fertilizer used to grow grain and from cattle belching.
The study notes research that says dietary choices will become critical to meeting emissions targets under the Paris climate agreement as global demand for food rises with a growing population.