But consumers can make small changes to bring that number down, said Rebecca Boehm, a postdoctoral fellow at the Rudd Center for Food Policy and Obesity at the University of Connecticut and lead author of the study. It’s a simple matter of watching your budget, your “food miles” and — most important — your consumption of meat and dairy.
“If people reduced their spending on protein foods by 18 percent, they’d see almost a tenfold reduction in household greenhouse gas emissions,” Boehm said. “That is pretty significant.”
Below, find Boehm’s other evidence-based tips for shrinking your diet’s carbon footprint.
Step one: Eat less red meat and dairy
Studies consistently show that animal agriculture is the most carbon-intensive type of farming, in part because livestock such as cows and sheep produce methane as part of their digestive processes. To further compound the issue, Americans eat lots of red meat: 54 pounds per person last year, according to the Agriculture Department.
Some researchers have urged people to go vegan, citing the climate gains. (An economist at Oxford did exactly that in May.) But Boehm says smaller changes, such as the 18-percent reduction, could also go a pretty long way. That’s particularly true if people make up the difference with less-intensive proteins, such as seafood, poultry and beans.
What about grass-fed beef or other, more sustainable meat and dairy products? In a speech earlier this year, the head of the United Nations’ Food and Agriculture Organization argued that a “low-carbon livestock sector is possible to achieve” through climate-friendly farming practices.
Boehm wouldn’t fully endorse that, either: Research suggests that trading beef for something like chicken cuts emissions more than switching between different types of beef.
“It’s more impactful,” she said, “to switch to plants or seafood or poultry.”
Step two: Buy local vegetables — and, randomly, melons
Compared to red meat, produce doesn’t have much of an on-farm carbon footprint. But that changes once the fruits and veggies leave the farm. Boehm’s study shows that vegetables and melons generate particularly high emissions during transport — probably because they travel long distances on refrigerated trucks to restaurants and stores.
That means consumers may want to buy vegetables and melons locally, Boehm said, whether from a retailer that sources local products or at a farmers market or farm stand. For many consumers, this rule limits when they can eat certain foods: no more asparagus or watermelon in the offseason.
Should concerned eaters start buying everything local? That would cut emissions from transportation. But Boehm said that, for most types of foods, there’s no point in worrying about it.
“For certain industries, like vegetables and melons, the postproduction emissions are a large share of total emissions,” she said. But you don’t see that same ratio in, say, rice, dairy or snacks.
Step three: Shop at stores and restaurants that watch their emissions
Discussions about food and greenhouse gas emissions tend to focus on farms. But Boehm says that’s only half the picture: Emissions are also a major problem at grocery stores and restaurants.
“It’s not just about the food you eat — it’s about all the other things that are required to bring the food to you,” she said. “That includes things like the electricity to light restaurants or to cook food in them.”
Boehm admits that it’s difficult for consumers to prompt change at the industry level — but they can support businesses that are documenting and reducing their carbon emissions. One restaurant group in Portland, Ore., has published dish-by-dish emission data online. The Zero Foodprint project helps restaurants calculate and offset their carbon footprints. Major grocery chains, including Walmart and Meijer, have also tweaked their supply chains to reduce emissions.
In the future, Boehm plans to look at whether ditching restaurants altogether would reduce a household’s food emissions — but there’s no data to support that now, she said.
Step four: Cut your food budget, if you can
Boehm acknowledges that this tip is the most abstract — and for some, it wouldn't be practical or nutritious. But the economic logic is that the cost of food frequently reflects the cost of the resources that went into it, and those resources also draw on the environment.
Consider a bag of carrots. The carrots require resources on the farm, from soil and water to harvesting machines. But when a consumer buys carrots at the store, they're also paying for the plastic bag the carrots came in, the design team that designed the bag, and a lot of other distant corporate activities.
High-income households tend to buy a lot more resource-intensive — read: expensive — food, as well as more red meat and dairy products, Boehm said.
Reducing spending does not make sense if it makes your diet less healthful, Boehm said. She and other researchers have found that many processed and packaged foods — such as chips and Twinkies — generate fewer emissions because they’re made from grains and other ingredients that do not have a large carbon footprint.
Here, as with all attempts to reduce emissions, it's important to make careful substitutions.
“If people are going to switch, what do they switch to?” Boehm asked. “That's an area for future research in the U.S.”