WWS Study: Shift in U.S. diets may have environmental benefits
A shift in Americans' diets from beef to poultry or vegetarianism could have major environmental benefits, according to a new Woodrow Wilson School study. The study, by Simon Donner, a research associate at the School's Program in Science, Technology and Environmental Policy, finds that the emergence of a large "dead zone" each summer in the Gulf of Mexico -- an area of oxygen-depleted waters fuelled by nitrogen from the Mississippi River -- could be mitigated by a shift in diet.
The study, titled "Surf or turf: A shift from feed to food cultivation could reduce nutrient flux to the Gulf of Mexico," was published in a recent issue of the journal Global Environmental Change.
Fertilizer used on crops in the central United States contributes nitrogen to the rivers and streams across the Mississippi River Basin. The Mississippi River delivers some of this nitrogen, primarily in the form of nitrate, to the Gulf of Mexico, where it promotes the production of algae during the spring and summer. The algae material sinks and decomposes, consuming oxygen from the bottom waters. This process causes a large area of hypoxia, known as the "dead zone," to emerge in the northern Gulf during the summer, threatening fisheries and the health of the ecosystem.
The majority of the nitrogen fertilizer is applied to grain crops that are used to produce animal feed. Donner's study demonstrates how, by shifting from a beef-oriented diet to a vegetarian diet or poultry-based diet, the extent of seasonal hypoxia, or oxygen-depleted waters, can be dramatically reduced. The author asserts that cultivating crops that would support vegetarian diets, or diets with only poultry rather than beef, would reduce fertilizer usage and the nutrient pollution that causes the dead zone. Donner proposes land-use scenarios and other mitigation proposals that could potentially reduce total land and fertilizer demands by over 50% without any change in total food production.
"What the study shows is that if we really want to address environmental problems like hypoxia in the Gulf, we need to be thinking about the way we produce our food," Donner said. "Grain-fed beef is the biggest problem, because so much land and fertilizer is needed just to grow the feed for cattle. We don't have to give up beef entirely, of course, just produce and eat less of it."
His work is a departure from previous research as it addresses the hypoxia problem from the perspective of food production and dietary choices. Donner also underscores the importance of dietary transition in a successful nutrient management policy, in light of other mitigation proposals, recent dietary trends and other future land-use projections.
The author uses data from the U.S. Department of Agriculture and ecological models to demonstrate how a theoretical shift in feed cultivation would reduce nitrogen fertilizer use and nitrate delivery by the Mississippi River.
Crop production and fertilizer use statistics are used to estimate the area of land and amount of fertilizer used to grow the six primary feed crops (corn, soybeans, sorghum, barley, oats and wheat) in the Mississippi Basin. The ecological models then simulated the cycling of water, carbon and nitrogen through natural and agricultural ecosystems across the Mississippi River Basin and the delivery of water and nitrate to the Gulf of Mexico under alternative diet scenarios.
Donner's work reveals that over 70% of the grain produced in the Mississippi Basin area, such as corn, is used to feed livestock. Soy and corn are the prominent feed crops and account for 94% of the production of feed crops in the Basin. The author estimates that 63% of non-dairy feed is allocated to beef production.
In exploring alternative food production scenarios, Donner first looks at replacing beef and pork protein with vegetarian protein using the same crops -- in terms of type and quantity -- currently cultivated. In the second, Donner's investigates using a mix of the crops suited to a vegetarian diet to replace the meat protein. The author finds that the alternative food production scenarios resulted in a 53-59% decrease in the demand for feed crops and a 49-56% decrease in the need for nitrogen fertilizer. The change could reduce nitrate export to the Gulf of Mexico by 49-54%, to levels at which the hypoxic zone has, in the past, been small or non-existent.
The author concedes that while a shift away from the cultivation of feed for meat production would address the hypoxia problem it would be difficult to implement in practice. As a potential alternative strategy, in the study Donner suggests that a reduction in feed cultivation should be combined with the construction of wetlands by major waterways, and improved fertilizer management.