Animal agriculture is a major contributor to environmental degradation. Its responsible for air and water pollution, production of approximately one-fifth of global greenhouse gas emissions, massive land use, and threats to biodiversity.

This paper, published in the Proceedings of the National Academy of Sciences, compares the environmental costs of beef, dairy, poultry, pork, and eggs in terms of land use, water use, contribution to reactive nitrogen overabundance in the ecosystem, and greenhouse gas emissions. The authors divide environmentally-destructive inputs, such as volume of irrigated water required, by units of caloric or protein mass outputs, such as per 1,000 kilocalories, for each animal category. Additionally, the authors calculate the amounts of resources needed to produce potatoes, wheat, and rice in the same way as a basis of comparison. The data used for these calculations comes from U.S. federal reports published between the years 2000 and 2010.

The authors find that “Beef is consistently the least resource-efficient of the five animal categories in all four considered metrics . . . Producing 1 megacalorie of beef requires ≈28, 11, 5, and 6 times the average land, irrigation water, GHG [greenhouse gases], and Nr [reactive nitrogen] of the other animal categories.” Additionally, from their comparisons with plant foods, the authors conclude that “policy decisions designed to reduce animal-based food consumption stand to significantly reduce the environmental costs of food production.” This study’s results may impact both government policies and consumers by revealing the comparative environmental consequences of food choices.

[Contributed by Mona Zahir]