Source: Julie Larson Bricher, MEATINGPLACE, 3/23/18



Individuals who lower their caloric intake and animal-based food consumption may have an aggregate impact on reducing greenhouse gases (GHGs), according to researchers at the University of Michigan and Tulane University.

In a data analysis, researchers forecast that the 20 percent of U.S. diets with the highest carbon footprint accounted for 46 percent of total diet-related GHGs, and about eight times more emissions than the lowest quintile of diets. And beef consumption accounted for 72 percent of the emissions difference between the highest and lowest groups, according to the study.

The study has been published in the journal Environmental Research Letters and was funded by the Wellcome Trust, a biomedical research charity based in London. The researchers analyzed data already contained in databases to estimate the impact of U.S. dietary choices on GHG emissions, creating a database that evaluated the environmental impacts involved in producing more than 300 types of foods.

"Reducing the impact of our diets — by eating fewer calories and less animal-based foods — could achieve significant reductions in greenhouse gas emissions in the United States," Martin Heller, a researcher at the UM Center for Sustainable Systems in the School for Environment and Sustainability, said in a university press release.

The study estimated the GHG emissions associated with food production only, not the processing, packaging, distribution, refrigeration and cooking of those foods, which, if included, would likely increase total emissions by 30 percent or more, Heller said.

Debate
The study making the diet-GHG link is only the latest voice heard in the debate over the meat industry’s overall role in greenhouse gas emissions, dating back to the U.N. Food and Agriculture Organization’s “Livestock’s Long Shadow” report in 2006.

Other studies have suggested that eliminating food animals from diets or from U.S. production would not appreciably reduce greenhouse gases and would increase nutrient deficiencies. For example, in an October 2017 study, researchers from Virginia Tech and USDA Agricultural Research Service determined that eliminating food animals from U.S. production would reduce greenhouse gas emissions by only 28 percent, because the need to produce additional food crops and use more synthetic fertilizer to replace manure would prompt their own associated GHG increases. That would represent a drop of only about 2.6 percent of total U.S. emissions. In addition, eliminating animal-based foods from the diet would increase deficiencies in calcium, vitamins A and B12 and some important fatty acids.

In response to the UM/Tulane study, Sara E. Place, the National Cattlemen’s Beef Association’s senior director for sustainable beef production research, noted in a statement provided to Meatingplace, “The paper by Heller and others is quite comprehensive but has the same challenges as many diet-related GHG assessments.” In summary, she said, the study assumes that current life cycle estimates of environmental impacts of different food items would apply even when the whole food system has changed dramatically – such as a significant portion of  the U.S. dietary patterns -- when in fact this is unknown. 

Place also faulted the study for assuming a single or very narrow range of carbon footprints for individual food items, when those data points are changing all the time. “For example, U.S. beef’s carbon footprint declined by 16 percent from 1977 to 2007, according to research published in the Journal of Animal Science,” she said.

Carbon footprints are just one component of sustainability, whereas a more holistic approach takes into account tradeoffs, such as the fact that ruminant animals, while producing more methane, also digest plants that are inedible by humans and so make use of land resources that may otherwise be useless as a source of food.

“Using single factors such as carbon footprints to assess the sustainability of diets may lead us to conclusions that are not holistically sustainable for our food system to responsibly meet human nutrient requirements,” Place said. 

What about cars?
According to the Environmental Protection Agency, livestock, the commodity group most criticized in the present study, is responsible for 3.8 percent of all GHG emissions. U.S. livestock production has a far lower carbon footprint than the U.S. transportation sector’s footprint of 27 percent and the energy sector’s footprint of 31 percent.

“In short, what we eat matters environmentally to some degree, but it pales compared to what we drive or how we use energy. So, have the burger. Just make sure you walk to the restaurant," said Frank Mitloehner, professor and air quality extension specialist for the Department of Animal Science at the University of California-Davis.

For more stories, go to www.meatingplace.com.