Study examines ‘carbon hoofprint’ of American cities

University of Michigan – Research from the University of Michigan and the University of Minnesota published in the journal Nature Climate Change on Oct. 20 provided a first-of-its kind, systematic analysis that digs into the environmental impacts of the sprawling supply chains that the United States relies on for its beef, pork and chicken.

The team calculated and mapped those impacts, which they’ve dubbed meat’s “carbon hoofprint,” for every city in the contiguous U.S. While the study does underscore the size of America’s urban carbon hoofprint — it’s larger than the entire carbon footprint of Italy — it also provides city-specific information that residents and governments can use to make positive changes.

“This has huge implications for how we gauge the environmental impact of cities, measure those impacts and ultimately develop policies to reduce those impacts,” said Benjamin Goldstein, a leader of the study and assistant professor at Michigan’s School for Environment and Sustainability.

For example, policymakers have rolled out campaigns and initiatives that help homeowners reduce their carbon footprints by incentivizing and subsidizing things like installing solar panels and insulation, he said. These projects can still cost thousands, if not tens of thousands, of dollars.

“But if you just cut out half of your beef consumption and maybe switch to chicken, you can get similar amounts of greenhouse gas savings depending on where you live,” Goldstein said. “If we can get people to use this type of study to think about how diets in cities impact their environmental impacts, this could have huge effects across the United States.”

It would be natural to assume cities with higher meat consumption per capita would have a higher per capita hoofprint. But the team found the correlation between those variables was actually quite low.

Other obvious candidates are the emissions from transporting meat from the rural areas where it’s produced to the cities that consume it. While that is a piece of the puzzle, the researchers found it’s not a particularly big one.

“There’s not a single emissions value for the meat we consume,” said Rylie Pelton, a research scientist at the University of Minnesota’s Institute on the Environment and co-leader of the study. “That’s because the supply chains are different in different locations. And also the impacts of production, the ways that beef, chicken, pork and feed are produced, are different in those different locations. That all matters from an emissions standpoint.”

For example, Los Angeles’ beef comes from processing facilities in 10 counties. But the meat that’s processed in those facilities comes from livestock raised in 469 counties by feed that’s sourced from 828 counties.

Each stop and product along that supply chain has its own processes with an associated carbon footprint, such as using fertilizer for growing feed and managing manure on farms. That’s combined with transporting a variety of goods across the physical extent of the full chains, which can stretch thousands of miles. The team considered these wide-ranging factors in evaluating the carbon hoofprint for more than 3,500 locations.