The U.S. is the leading producer of milk, beef, chicken and poultry, and second in pork, eggs and game meat worldwide. This has primarily been achieved via highly efficient agricultural practices that are increasingly coming under fire from environmental activists. That's particularly concerning in light of the recent United Nations prediction that the global population will grow to 9.5 billion people in the year 2050.

Jude Capper, Washington State University assistant professor of dairy sciences, recently told the 71st Cornell Nutrition Conference that the “intuitively correct” food choice is often the least environmentally friendly option.

“As a food industry, we must use a whole-system approach and assess environmental impact per gallon of milk, pound of beef or dozen eggs, not per farm or per acre.”

She says this important distinction is the basis of a life-cycle assessment (LCA) approach, which evaluates all inputs and outputs within the food-production system and allows the correct comparison of different production systems.

Capper was referring to the paper “Demystifying the Environmental Sustainability of Food” that she co-authored with Roger Cady, Elanco senior technical consultant, and Dale Bauman, Liberty Hyde Bailey Professor at Cornell University. See it at wsu.academia.edu/documents.

Capper points out that in 2007, the U.S. dairy industry produced 8.3 billion more gallons of milk than in 1944, but due to improved productivity, the carbon footprint of the entire dairy farm industry was reduced by 41% during the same time period.

Similarly, pasture- or grass-fed meat is growing in popularity partly due to the perception it's more eco-friendly than conventionally produced beef.

“However, the time needed to grow an animal to slaughter weight is nearly double that of animals fed corn,” Copper says. “This means that energy use and greenhouse gas emissions per pound of beef are increased three-fold in grass-fed beef cattle. In total, finishing the current U.S. population of 9.8 million fed cattle on pasture would require an extra 60 million acres of land. Again, the intuitively environmentally friendly option has a far higher resource and environmental cost.”

Another emerging trend among American consumers is the desire to purchase food grown locally. “Often ‘locally grown’ food is thought to have a lower environmental impact than food transported over long distances due to carbon emissions from fuel,” explains Capper. The phrase “food miles” has become a popular buzzword, defined simply as the distance that food travels from its place of origin to its place of final consumption.

“Although well-intentioned, it's incorrect to assume that the distance that food travels from point of origin to point of consumption is an accurate reflection of environmental impact,” Capper says. “This simplistic approach fails to consider the productivity of the transportation system, which has tremendous impact on the energy expended per unit of food.”

As an example, one dozen eggs transported several hundred miles to a grocery store in a tractor-trailer that can carry 23,400 dozen eggs is a more fuel-efficient, eco-friendly option than a dozen eggs purchased at a farmers' market (4.5 times more fuel used) or local farm (17.2 times more fuel used).

“The high-capacity vehicles used in modern transportation systems improve productivity, allowing food moved over long distances to be highly fuel-efficient and environmentally friendly compared to locally grown food,” Capper explains.

The desire to protect the environment and to do so, in part, by altering personal behaviors is admirable, Capper says. However, she emphasizes that those personal decisions must be based on logic rather than intuition.

“Consumers might think they are making the responsible, virtuous food choices, when, in truth, they are supporting production practices that consume more natural resources, cause greater pollution and create a larger carbon footprint than more efficient, technology-driven, conventional methods,” she concludes.