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Eating less beef is essential to ensuring a sustainable food supply in the coming decades, according to an April 20 working paper whose co-authors include University affiliates Timothy Searchinger and Xin Zhang.

"When you count the land use implications of meat diets, and above all beef, the greenhouse gas emissions are much, much, much higher than vegetarian or more vegetable-oriented diets," said Searchinger, a research scholar in the Wilson School.

Searchinger serves as a senior fellow at the World Resources Institute, the global research organization that released the report.

The paper probably offers today's most detailed and accurate global analysis of actual diets and their greenhouse gas emissions and land use requirements, Searchinger said. It finds that reducing beef consumption is even more important than previous studies have shown, he added.

Without intervention, global demand for calories in 2050 will exceed the supply of calories, as measured in 2006, by 70 percent, the report states.

The researchers trace the "food gap" to projected demographic shifts. A population spike of 133 percent will mean more mouths to feed. Furthermore, the average person will eat more calories, protein and animal-based products due to trends like urbanization, increasing household wealth and the commercialization of agriculture, according to the report.

Problematically, demand for beef will increase by 95 percent, compared to 79 percent for all animal-based food, between 2006 and 2050, the paper predicts.

Searchinger attributed beef's popularity to its great taste and long history as a staple source of protein within many societies. He explained that the ease involved with raising cows might have led to the start of the trend.

Beef uses more land and fresh water and emits more greenhouse gases per unit of protein than any other common food during production, the report notes. Even relative to other livestock categories, beef requires 28 times more land per calorie consumed. If demand for beef continues to rise, natural forests and savannas could be destroyed, the report adds.

In the United States, the report found that nearly 90 percent of the land used and nearly 85 percent of the greenhouse gases emitted to feed the average person in 2009 came from animal-based food. Beef alone accounted for almost half of U.S. agricultural land use and emissions.

Cutting U.S. beef consumption per capita to reach the world average, a reduction of over 70 percent, would lower production-related land use and greenhouse gas emissions by about a third each.

If half of Americans became vegetarian, the per capita land use and greenhouse gas emissions from food production would decrease by about 50 percent.

University of Oxford Professor Charles Godfray, who also directs the Oxford Martin Programme on the Future of Food and serves on the United Nations Committee on World Food Security, described the study as excellent and very important.

Mark Barthel, a partner at the sustainable advising company 3Keel, has translated environmental findings into action at the United Nations, international businesses and non-governmental organizations; according to him as well, the report was clear, well-written and well-evidenced. The report’s recommendations seem realistic in terms of targeting over-consumption, rather than demanding major dietary changes, he said.

Compared to past reports, Godfray said, the study includes minor differences in methodology and assumptions, but adds to a growing body of evidence that shows that people must shift their diets, especially by lowering animal-based consumption. Godfray agreed with the conclusion that eating less beef represents the single most important step toward a more sustainable food system.

The paper marks one of several studies that quantifies the magnitude of the issue, providing statistical evidence that experts lacked several years ago, he added.

The GlobAgri-WRR model used in the report was a version of the GlobAgri model developed by the Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Princeton University, the Institut National de la Recherche Agronomique and WRI.

Searchinger said GlobAgri, of which he was one of the two main developers, gained more biophysical detail than past models by excluding economic considerations. Economic considerations, which measure the extent to which one person eating more causes another person to eat less, would add too much complexity and uncertainty, and they are unnecessary for identifying which combinations of dietary changes and improvements in agriculture would produce a certain amount of food at an acceptable environmental cost, he said.

GlobAgri includes a nitrogen model mostly developed by Zhang, then a postdoctoral research associate at the Wilson School and the Princeton Environmental Institute and now an assistant professor at the University of Maryland Center for Environmental Science.

Zhang described her model and data sets as the first of their kind to examine patterns of nitrogen fertilizer use by nation and by crop type over the past half-century. Nitrogen fertilizer is known for releasing the greenhouse gas nitrous oxide.

"By looking into the historical trends in the different countries, you can gain insights in terms of how the economic growth and food demand changes might affect the nitrogen use efficiency and the nitrogen loss to the environment," Zhang said.

She added that she hopes to identify technologies, policies and socioeconomic opportunities that increase the efficiency of nitrogen fertilizer use, which currently enables crop production relied on by almost half of the world population.

The report focuses on the diets of certain groups especially.

"The people who should and need to hold down their meat consumption… and generally livestock product consumption are those who are eating far more than they could possibly need," Searchinger said, referring to about two billion people in the United States, Canada, Latin America, the Middle East, North Africa and the European Union.

He added that societies growing wealthier, like China, should take special care to avoid overconsumption.

The key to shifting diets is not nagging people, but rather offering more attractive alternatives, Searchinger said. For example, he is increasingly hopeful that cheaper, non-meat products that taste like meat will become mainstream, even in the next few years.

Up until now, most efforts to shift diets have depended on information and education campaigns, which have proven inadequate, according to the report. The researchers call for approaches that influence unconscious decision-making by presenting food choices differently.

Called the Shift Wheel, the paper's plan for affecting consumer psychology is a sensible account based on what researchers know so far, Godfray said, using relatively good data despite some missing information.

"Policy has to be developed now. We just can't say, 'Well, we don't have enough data,' so we have to make optimal use of the data that we do have available," Godfray said.

But he added that experts need to conduct experiments on individuals, groups and countries to test the effectiveness of each Shift Wheel strategy. Searchinger confirmed that WRI will soon start a project to work with companies to help investigate these options.

The report notes that insufficient data on what foods people buy poses a major obstacle to influencing choices.

Barthel said the other main challenge is convincing consumers that eating sustainably will serve their self-interest.

"Human nature is very self-absorbed, so if you can find a really good way of communicating a new personal benefit to someone, they are far more likely to make a change in their diet," he explained.

While the Shift Wheel only focuses on personal behavior changes, Godfray suggested intervening by altering food prices in order to change consumer choices as well.

The study also recommends creating a dedicated funding mechanism for this project, as well as an initiative that would gather experts across many disciplines and sectors to focus on modifying people's diets. Neither of these ideas has come to fruition yet.

However, Barthel noted there is already such an initiative. The United Nations Environment Programme 10-Year Framework of Programmes, he explained, includes a sustainable food systems program that contains dietary shift issues and gathers representatives of over a hundred countries, most major non-governmental organizations, UN agencies, private sector companies and the other stakeholders that the report is seeking.

"What we need to do is coalesce a range of interests and actors around that program to make it more effective… rather than necessarily starting from scratch," he said.

Titled "Shifting Diets for a Sustainable Food Future," the paper marks the 11th and last installment of the "Creating a Sustainable Food Future" series, of which Searchinger is the technical director. His team will publish a final volume summarizing all the work, still using GlobAgri to explore options for a sustainable food future, in a few months.

Searchinger said the volume will try to answer the question, "What combinations of diet changes, improvements in yields, changes in meat production practices, changes in general agricultural practices… could be done so that we could produce all the food that the world needs in 2050, and do it without chopping down more forests and with an acceptable level of greenhouse gas emissions?"

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