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Many cities, from New York to Los Angeles, are working to reduce the amount of carbon they pump into the atmosphere—from helping residents upgrade to more energy-efficient appliances to devoting resources to public transit. But few have tallied the impacts of one important part of urban life—the meat we eat.
A new study looks to fill that gap. A team of researchers mapped the supply chains that funnel meat to residents of 3,531 different cities across the United States, and determined how much carbon these activities release into the atmosphere, which they termed the “carbon hoofprint.” It’s the first time that researchers have calculated the pollution emitted from raising the beef, pork, and chicken U.S. citizens eat for every town and city in the country.
Some of the numbers are staggering: The carbon hoofprint of all U.S. cities combined is larger than total carbon emissions of the entire United Kingdom or Italy, and roughly equivalent to the total emissions from fossil fuel combustion in all homes in the U.S. The study was published recently in Nature Climate Change.
“There’s huge variation between cities,” says Benjamin Goldstein, head of the Sustainable Urban-Rural Futures lab at University of Michigan and one of the authors of the study. Though per capita meat consumption is about the same across U.S. cities, per capita hoofprints vary by a factor of three from biggest to smallest. What matters is how the meat is sourced, and to a lesser degree, the kind of meat consumed. Beef has the biggest climate impact for nearly 99 percent of cities. “It’s the most environmentally intensive by far,” says Goldstein. In just a few cities, pork took the top emissions spot. Chicken and pigs tend to be grown closer to cities and require less feed, water, and land to grow.
In some cases, reducing meat consumption would have more impact than replacing appliances.
The findings revealed some overarching patterns, and many regional variations. U.S. residents consume more than 11 metric tons of meat a year, with the three largest cities—New York City, Los Angeles, and Chicago—accounting for almost one third of that. New York and Los Angeles also ranked highest on the hoofprint scale. The scientists maps’ of meat supply chains, which they termed “meatsheds,” show how sprawling these networks can be: According to the scientists’ model, for instance, Los Angeles sources much of its beef from 10 counties, which are supplied with livestock from 469 counties, which in turn, rely on feed grown in 828 counties.
In some cases, reducing meat consumption would have more impact on the climate than replacing energy-intensive appliances or switching lightbulbs, says Goldstein. “We are telling people to invest tens of thousands of dollars in solar panels and batteries,” he says. “I think we should do that, but a much cheaper and quicker way to reduce the carbon footprint of your household might be to just cut 50 percent of your beef and put it toward chicken and pork instead, or, heaven forbid, tofu.” Eating more chicken, less beef, could cut emissions by up to a third, Goldstein and his colleagues found. Reducing food waste, another 16 percent.
Some cities are explicitly looking at ways to reduce the climate impact of their residents’ meat consumption. For example, in New York City, the Plant-Based Carbon Challenge is a voluntary leadership initiative for NYC’s private sector to draw down food-related carbon emissions. Los Angeles has signed on to a pledge to reduce carbon emissions from food by 25 percent in city institutions, but leaders are also looking up the supply chain and thinking about how the city can work with rural communities to reduce impact, Goldstein says. “I think we’re getting there—the horizons of urban sustainability are broadening.”
The study does a good job of bringing to light the invisible threads that connect urban dwellers and their rural counterparts, says Anu Ramaswami, an environmental engineer at Princeton University, whose previous work has looked at how supply chains outside of cities’ borders support life inside of them. Ramaswami, who was not involved in the current study, says that it was innovative for the researchers to model everything from the feed to the processing to the shipment of the meat itself. “For beef, there’s as much emissions coming from producing the feed as in growing and processing the cattle,” she says. “I think this is the innovation, where they’ve modeled the nearby processors and then the feed.”
Goldstein says he hopes that the research forces city dwellers and urban policy makers to think more deeply about food systems as a core component of urban sustainability. For a long time, cities looking to boost their sustainability have focused on things like transportation, building, energy, waste management, water systems—because these forms of infrastructure are within the city and also under cities’ direct control.
“The hoofprint can be a substantial piece of a city’s carbon footprint, and we need to really address our climate change impacts across all sectors,” he says. “I hope that this paper gives some food for thought—no pun intended.” 
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Lead image: Aleksandar Malivuk / Shutterstock
