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Most low- and middle-income countries will require a substantial increase in greenhouse gas (GHG) emissions and water use due to their efforts to increase food production as these countries try to fight hunger, finds a new research from the Johns Hopkins Center for a Livable Future based at the Johns Hopkins Bloomberg School of Public Health.

Obesity, undernutrition, and climate change are major global challenges that impact the world’s population. While these problems may appear to be unrelated, they share food production and consumption as key underlying drivers. By recognizing the role of food production in climate change, this study examines the challenges of simultaneously addressing hunger and the climate crisis at both the individual and country levels.

The scientists developed a model that assessed how alterations to dietary patterns across 140 countries would impact individual- and country-level GHG emissions and freshwater use.

They used this model to assess the per capita and whole country climate and water footprints of nine plant-forward diets. The plant-forward diets examined ranged from no red meat, pescatarian, lacto-ovo vegetarian, and vegan, among others.

A key finding of the study (Brent F. Kim, Raychel E. Santo, Allysan P. Scatterday, Jillian P. Fry, Colleen M. Synk, Shannon R. Cebron, Mesfin M. Mekonnen, Arjen Y. Hoekstra, Saskia de Pee, Martin W. Bloem, Roni A. Neff, Keeve E. Nachman, “Country-specific dietary shifts to mitigate climate and water crises”, Global Environmental Change, 2019) showed that a diet in which the animal protein came predominantly from low food chain animals, such as small fish and mollusks, had nearly as low of an environmental impact as a vegan diet.

The scientists determined that a diet that involved reducing animal food consumption by two-thirds – termed by study authors as “two-thirds vegan” – generally had a lower climate and water footprint than the more traditional lacto-ovo vegetarian diet.

A food’s country of origin can have enormous consequences for climate, according to the study. For example, one pound of beef produced in Paraguay contributes nearly 17 times more GHG than one pound of beef produced in Denmark.

Often, this disparity is due to deforestation resulting from grazing land.

“Our research indicates there’s no one-size-fits-all diet to address the climate and nutrition crises. Context is everything, and the food production policies for each country must reflect that,” says senior author of the study, Keeve Nachman, PhD, director of the Food Production and Public Health program at the Johns Hopkins Center for a Livable Future and an assistant professor with the Bloomberg School’s Department of Environmental Health and Engineering.

To counter these climate impacts and to address diet-related morbidity and mortality, the authors recommend, based on this report, that high-income countries accelerate adapting plant-forward diets.

The authors emphasize that an examination of these diets and their environmental footprints allows for consideration of dietary recommendations or behavioral changes that would balance health and nutrition needs, cultural preferences, and planetary boundaries.

The methodology used in the study allows for new data-driven comparisons between countries and regions, and also takes into account the different contexts and conditions in these countries.

The study integrates country-specific data such as current food availability and trade and import patterns with information about greenhouse gas and water use burdens that are associated with the production of specific food items by country of origin.

It also takes into account the carbon emissions associated with land use changes for purposes of food production.

“Our data indicate that it is actually dairy product consumption that explains much of the differences in greenhouse gas footprints across diets. Yet, at the same time, nutritionists recognize the important role dairy products can have in stunting prevention, which is a component of the World Bank Human Capital Index,” says study co-author, Martin Bloem, MD, PhD, director of the Johns Hopkins Center for a Livable Future and the Robert Lawrence Professor of Environmental Health at the Bloomberg School. The World Bank’s Human Capital Index calculates the contribution of health and education to the productivity of future generations of workers.

“The study findings highlight the difficulty in prescribing broad dietary recommendations to meet the needs of individual countries,” says Bloem.

The study found:

“In a scenario in which all 140 study countries adopted the average consumption pattern of high-income OECD countries, per capita diet-related GHG and consumptive (blue plus green) water footprints increased by an average of 135 and 47 percent, respectively, relative to the baseline. These findings echo prior literature on the climate implications of rising meat and dairy intake, and the importance of both reducing animal-product intake in high-consuming countries and providing viable plant-forward strategies for transitioning countries.”

The scientists modeled scenarios in which dietary patterns could better align with ecological goals alongside nutrition guidelines — while also identifying some of the challenges in doing so. For example, baseline protein and caloric availability were below recommended levels in 49 and 36 percent of countries, respectively. The resulting adjustments for under-consumption attenuated — and in some cases completely offset — the GHG and water footprint reductions associated with dietary shifts. For a scenario in which all 140 study-countries adopted either the low red meat or meatless day diet, our model projected an average net increase in diet-related GHG, blue water, and green water footprints relative to the baseline. Populous countries characterized by under-consumption were the largest contributors to this phenomenon, namely India and to a lesser degree Pakistan and Indonesia; loss-adjusted baseline protein availability in these countries was 14, 9, and 12 g below the recommended minimum of 69 g, respectively. Thus, interventions that aim to address both sustainability and health goals must ensure plant-forward shifts are ambitious enough to offset the potential ecological burdens associated with providing adequate nutrition.

The study report said:

“A country-specific analysis reveals, for example, that shifting to the meatless day diet reduced GHG and water footprints in 47% and 57% of study countries, respectively — with some of the greatest per capita reductions in Paraguay, Israel, and Brazil — even though the average net effect was an increase in footprints.”

It said:

“A number of country governments, including Brazil and more recently Canada, have put forth dietary guidelines emphasizing predominantly plant-based foods. While this is a critical step toward aligning domestic consumption patterns with public health and ecological goals, countries’ production and export patterns merit additional attention. Brazil, for example, was the top exporter of bovine meat (based on an average of 2011–2013 data) and was in the top quartile for GHG-intensity of bovine meat production. Together with other major GHG-intensive exporters such as India and Paraguay, Brazilian bovine meat exports contributed to the large GHG footprints of diets in importing countries like Chile, Hong Kong, Kuwait, Venezuela, and Israel. In a hypothetical scenario in which the share of Hong Kong’s bovine meat imports from Brazil came from Denmark instead, Hong Kong’s per capita GHG footprint for the baseline pattern was 18% lower. While not necessarily feasible or desirable, this scenario further illustrates the importance of accounting for trade patterns and COO.”

The report said:

“The countries with the most GHG-intensive baseline consumption patterns — and the greatest potential GHG reductions from shifting toward plant-forward diets — included those with the highest per capita intake of bovine meat (Argentina, Brazil, Australia), the most GHG-intensive bovine meat production (Paraguay, Chile), and the greatest contributions of deforestation to the GHG footprints of diets (Paraguay, Chile, Brazil). Deforestation accounted for 61% of the GHG footprint for the Paraguayan baseline consumption pattern, and over 10% of the GHG footprints for 32 countries’ baseline patterns.”

It said:

“Over all 140 study countries, a theoretical shift to vegan diets reduced per capita diet-related GHG footprints by an average of 70%, relative to the baseline. Vegan diets had the lowest per capita GHG footprints in 97% of study countries. Given the low per-kilocalorie GHG footprints of most plant foods, even substantial increases in consumption had only modest effects on GHG emissions of diets. For the US vegan diet, for example, scaling up plant foods recouped 100% of the calories and protein from animal foods with only 16% of the GHG emissions relative to the adjusted baseline.

“Relative to vegan diets, low-food chain diets (i.e., predominantly plant-based plus forage fish, bivalve mollusks, and insects) offer greater flexibility by allowing for modest animal product intake with comparable environmental benefits. Low-food chain diets also met the recommended intake of vitamin B12 for adults in 49% of study countries, illustrating that there may be ways to mitigate this potential limitation of plant-forward diets even without supplementation, at least for the general population.

“Mostly plant-based diets were generally less GHG-intensive than lacto-ovo vegetarian diets, in part due to the relatively high GHG footprint of dairy (and eggs, depending on the basis of comparison) and the reliance on dairy as one of only three food groups in the lacto-ovo vegetarian diet used to meet the protein floor. This phenomenon was particularly notable for India. In 95% of countries, two-thirds vegan diets were less GHG-intensive than lacto-ovo vegetarian. Countries where this was not the case included those with some of the most GHG-intensive baseline consumption patterns (i.e., Paraguay, Chile, Argentina), largely because of the GHG-intensity of ruminant meat in those countries. In 64% of countries, the GHG footprints of no dairy diets were lower than those of lacto-ovo vegetarian diets (e.g., India and Indonesia. In 91% of countries, the GHG footprints of low-food chain diets were less than half those of lacto-ovo vegetarian diets. These findings suggest populations could do far more to reduce their climate impact by eating mostly plants with a modest amount of low-impact meat than by eliminating meat entirely and replacing a large share of the meat’s protein and calories with dairy.

“Per capita blue WFs of diets were in many cases largest in countries with 1) low annual precipitation, increasing reliance on irrigation for domestic crops; and 2) climatic factors such as high temperatures that contribute to high evapotranspiration rates, and thereby decrease crop water productivity (i.e., crop output per unit of water consumed). These included Iran, Egypt, and Saudi Arabia. Domestically-produced rice was among the top contributors in high-blue WF countries, four of which (Kazakhstan, Afghanistan, Pakistan, Iran) were also among the most blue water-intensive rice-producing countries. For blue WF reductions, the most impactful per capita dietary shifts were in Egypt, in part due to the high blue water intensity of Egyptian bovine meat and dairy.

“For baseline consumption patterns, the consumptive (blue plus green) WF was highest for Niger, 98% of which was attributable to green water. Domestically-grown millet was the largest single contributor (40%) to the consumptive WF of the baseline consumption pattern. Niger had by far the highest per capita millet supply of any country, and was the 3rd largest producer and 8th most water-intensive millet-producing country. The low water productivity of millet in Niger was attributable to low edible yield and high evapotranspiration rates. Inedible millet crop residues, however, provide fuel, construction materials, and livestock fodder, illustrating how sociocultural and economic provisions of agricultural goods must be considered alongside ecological outcomes.”

“Where you get your food from matters,” says Nachman. “Trade patterns have an important influence on countries’ diet-related climate and fresh water impacts.”

“It would be satisfying to have a silver bullet to address carbon footprints and the impact of food production; however, with problems as complex and global as nutrition, climate change, freshwater depletion, and economic development, that’s not possible,” says Bloem. “There will always be tradeoffs. Environmental impact alone cannot be a guide for what people eat; countries need to consider the totality of the nutritional needs, access, and cultural preferences of their residents. The good news is this research can be a part of the solution, as it now gives policymakers a tool to develop nationally appropriate strategies, including dietary guidelines that help meet multiple goals.”


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