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Addressing the Diet-Climate Connection

What we eat plays a significant role in climate change. In alignment with the United Nations’ annual climate change Conference of Parties (COP23) and the American Public Health Association’s annual meeting, which in 2017 is focused on “Creating the Healthiest Nation: Climate Changes Health,” the Johns Hopkins Center for a Livable Future (CLF) has highlighted resources regarding ways that everyone can address climate change – at the table.

How does the food system exacerbate climate change?

By 2050, food production alone is expected to nearly exhaust the 2° C emissions budget

World leaders have agreed on the goal of keeping average global temperature rise within 2° C above pre-industrial levels in order to avoid the most catastrophic climate change scenarios. Even if this goal is met, climate change is projected to have significant global impacts, many of which will likely continue for centuries.[1]

food systemIn order to have at least a 66% chance of keeping global warming below 2° C, estimates indicate that global greenhouse gas (GHG) emissions from human activities must be kept at or below 21 ± 3 gigatons (Gt) of carbon dioxide equivalents (CO2e) per year.[2] Under the business‐as‐usual scenario modeled by Bajželj et al.[3], in which global population increases to 9.6 billion and global meat and dairy consumption increases with rising GDP, emissions from food production alone (20.2 Gt CO2e) would nearly exhaust the emissions budget in 2050. This projection includes emissions associated with land-use change, such as deforestation. Combined with non‐agricultural sectors, global emissions would greatly exceed 21 Gt, with severe consequences for people, public health, economies, and ecosystems. Additional studies have demonstrated the need for dietary shifts to mitigate climate change.[4],[5],[6],[7],[8]

Food system activities, including producing, transporting and disposing of food, generate up to 30% of total global GHG emissions.[9],[10] Of these sources, livestock production is the largest, accounting for an estimated 14.5% of global GHG emissions from human activities, according to the United Nations.[11] Meat and dairy from ruminant animals, such as cattle and goats, are particularly emissions-intensive.[12]

Globally about 30% of the food supply is never eaten.[13] If all the world’s food losses and waste were represented as a country, that “country” would be the third highest GHG emitter, after China and the U.S.[14] Discarding food is akin to discarding all the embodied GHG emissions involved in its production, processing, transportation, cold storage, and preparation.14 Additionally, when food decomposes in landfills, it generates significant quantities of methane, a GHG which is up to 84 times more potent than carbon dioxide.[15]

How can we mitigate climate change?

Dramatic reductions in meat and dairy consumption and wasted food, alongside reductions in GHG emissions from energy use, transportation, and other sources, are crucial for avoiding the most catastrophic climate change scenarios.

1) Cut wasted food

food wasteThe United Nations Sustainable Development Goal 12.3 calls for cutting wasted food in half by 2030.[16] The United States Environmental Protection Agency and U.S. Department of Agriculture have set the same goal.[17] According to estimates by climate scientists, meeting this goal alone can reduce projected food production-related carbon dioxide equivalents (CO2e) by 22% (4.5 Gt) in 2050.3 Interventions to reduce wasted food in higher‐income countries should focus on the consumer, including expiration date labeling and quality standards, improving shopping/eating practices, and controlling market supply. In lower- and middle-income countries, the greatest need for change is at the production end, including improvements to infrastructure, storage capacity, mechanization, packaging, and roads.

2) Eat healthy diets – with less meat and dairy

foodDiets that are high in plant-based foods and low in animal-based foods offer significant health benefits, along with climate and other environment benefits, including more efficient use of land, water, nitrogen, and other resources.[18],[19],[20] For example, researchers modelled potential GHG emissions reductions from a diet limiting intake of red meat (maximum of two 85g / 3 oz. portions per week), poultry (maximum of one 85g / 3 oz. portion per day), dairy (maximum of two 200g portions – about 2 cups – per day), eggs (5 per week), sugars, and oils to levels recommended by Harvard Medical School, WHO, FAO, and the American Heart Association, and sets a minimum for fruit and vegetable intake.3 That shift would entail, in part, a 31% reduction in global animal product intake relative to projected 2050 levels, with greater reductions in regions with higher intake. For example, Western Europe and North America would need to reduce red meat intake by 76% and 81%, respectively. Behavioral campaigns, such as Meatless Monday, can raise awareness of the impacts of dietary shifts, and introduce consumers to plant-based eating patterns.

What about grass-fed? Some advocates claim that by sequestering carbon from the atmosphere, grazing livestock can solve climate change. While grass-fed or pasture-raised animal products may offer many health, ecological, and animal welfare benefits compared to conventional animal products, they do not offer significant climate benefits. Under specific soil, climate, and animal density conditions, well-managed livestock grazing may sequester carbon, but this potential is small, time-limited, reversible, and substantially outweighed by the GHG emissions generated by grazing systems.[21]

What about local/regional? Eating local or regional foods may be a worthwhile practice for social and economic values, but should not be pursued as a major climate mitigation strategy. While choosing local sources for some types of foods can reduce GHG footprints (e.g., fresh berries or fish that would otherwise be shipped on planes), in other cases, local foods that require significant energy inputs to grow during the winter (e.g., tomatoes or lettuce grown in heated greenhouses) can have significant GHG footprints. When eating local, individuals and institutions should choose in-season foods, which are typically produced and transported with a lower climate impact.

Ultimately, changing the types of foods people eat and how those foods are produced is better for the climate than reducing the distances foods travel.[22] One study from the United Kingdom estimated that avoiding air-freighted and hothouse-grown foods could reduce dietary GHG emissions by 5%—compared with a 35% reduction from eliminating meat from diets.[23] Another study from the U.S. found that avoiding red meat and dairy one day a week reduces GHG emissions more than eating locally every day.22

3) Work for broader food system change

Shifting diets and reducing wasted food on an international scale will require more than just educating consumers. National and subnational policies that address dietary recommendations[24], agricultural subsidies, and procurement practices[25] will also need to support such transitions.[26]

What is the Johns Hopkins Center for a Livable Future doing?

Learn more


[1] Intergovernmental Panel on Climate Change. (2014). Climate Change 2014–Impacts, Adaptation and Vulnerability: Regional Aspects. Cambridge University Press.
[2] Rogelj, J., Hare, W., Lowe, J., Van Vuuren, D. P., Riahi, K., Matthews, B., ... & Meinshausen, M. (2011). Emission pathways consistent with a 2 [thinsp][deg] C global temperature limit. Nature Climate Change, 1(8), 413-418.
[3] Bajželj, B., Richards, K. S., Allwood, J. M., Smith, P., Dennis, J. S., Curmi, E., & Gilligan, C. A. (2014). Importance of food-demand management for climate mitigation. Nature Climate Change, 4(10), 924-929.
[4] Hedenus, F., Wirsenius, S., & Johansson, D. J. (2014). The importance of reduced meat and dairy consumption for meeting stringent climate change targets. Climatic Change, 124(1-2), 79-91.
[5] Bryngelsson, D., Wirsenius, S., Hedenus, F., & Sonesson, U. (2016). How can the EU climate targets be met? A combined analysis of technological and demand-side changes in food and agriculture. Food Policy, 59, 152-164.
[6] Aleksandrowicz, L., Green, R., Joy, E. J., Smith, P., & Haines, A. (2016). The impacts of dietary change on greenhouse gas emissions, land use, water use, and health: a systematic review. PloS one, 11(11), e0165797.
[7] Jones, A. D., Hoey, L., Blesh, J., Miller, L., Green, A., & Shapiro, L. F. (2016). A systematic review of the measurement of sustainable diets. Advances in Nutrition: An International Review Journal, 7(4), 641-664.
[8] Röös, E., Bajželj, B., Smith, P., Patel, M., Little, D., & Garnett, T. (2017). Greedy or needy? Land use and climate impacts of food in 2050 under different livestock futures. Global Environmental Change, 47, 1-12.
[9] Vermeulen, S. J., Campbell, B. M., & Ingram, J. S. (2012). Climate change and food systems. Annual Review of Environment and Resources, 37.
[10] Garnett, T. (2011). Where are the best opportunities for reducing greenhouse gas emissions in the food system (including the food chain)?. Food Policy 36, S23-S32.
[11] Gerber, P. J., Steinfeld, H., Henderson, B., Mottet, A., Opio, C., Dijkman, J., ... & Tempio, G. (2013). Tackling climate change through livestock: a global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO).
[12] Tilman, D., & Clark, M. (2014). Global diets link environmental sustainability and human health. Nature, 515(7528), 518-522.
[13] Gustavsson, J., Cederberg, C., Sonesson, U., Van Otterdijk, R., & Meybeck, A. (2011). Global food losses and food waste (pp. 1-38). Rome: FAO.
[14] Food and Agriculture Organization of the United Nations (2013). Food Wastage Footprint: Impacts on Natural Resources. Rome: FAO.
[18] Nelson, M. E., Hamm, M. W., Hu, F. B., Abrams, S. A., & Griffin, T. S. (2016). Alignment of healthy dietary patterns and environmental sustainability: A systematic review. Advances in Nutrition: An International Review Journal, 7(6), 1005-1025.
[19] Whitmee, S., Haines, A., Beyrer, C., Boltz, F., Capon, A. G., de Souza Dias, B. F., ... & Horton, R. (2015). Safeguarding human health in the Anthropocene epoch: report of The Rockefeller Foundation–Lancet Commission on planetary health. The Lancet, 386(10007), 1973-2028..
[20] Springmann, M., Godfray, H. C. J., Rayner, M., & Scarborough, P. (2016). Analysis and valuation of the health and climate change cobenefits of dietary change. Proceedings of the National Academy of Sciences, 113(15), 4146-4151.
[21] Garnett, T. et al. (2017). Grazed and confused? Ruminating on cattle, grazing systems, methane, nitrous oxide, the soil carbon sequestration question – and what it all means for greenhouse gas emissions. Oxford: Food Climate Research Network.
[22] Weber, C. L., & Matthews, H. S. (2008). Food-miles and the relative climate impacts of food choices in the United States. Environmental Science & Technology, 42(10), 3508-3513.
[23] Hoolohan, C., Berners-Lee, M., McKinstry-West, J., & Hewitt, C. N. (2013). Mitigating the greenhouse gas emissions embodied in food through realistic consumer choices. Energy Policy, 63, 1065-1074.
[24] Gonzalez Fischer, C. & Garnett, T. Plates, pyramids, planet: Developments in national healthy and sustainable dietary guidelines: a state of play assessment. (United Nations Food and Agriculture Organization and The Food Climate Research Network at The University of Oxford Rome, 2016).
[25] Health Care Without Harm. (2017). Redefining Protein: Adjusting Diets to Protect Public Health and Conserve Resources.
[26] Kim, B., Neff, R., Santo, R., & Vigorito, J. (2015). The importance of reducing animal product consumption and wasted food in mitigating catastrophic climate change. Baltimore, MD: Johns Hopkins Center for a Livable Future.