THERE IS MOUNTING EVIDENCE that a healthy, sustainable diet protects public health, the planet and our climate. But what, exactly, qualifies as a healthy, sustainable diet? A healthy, sustainable diet provides good nutrition and safe food; uses natural resources with a conservation mind-set; aims to reduce the incidence of non-communicable diseases associated with obesity and poor diets; rebuilds and nurtures ecosystems; and, we hope, mitigates climate change.
Climate change is one of the most visible ways that we are witnessing the degradation of ecosystems and the irresponsible use of natural resources—and our global diets are, in part, exacerbating the problems. By shifting our diets toward plants and away from meat—placing more emphasis on the obligation of high-income countries (HIC) to do so, as opposed to putting the onus on low- and middle-income countries (LMIC)—we not only make strides toward improved public health but also take steps toward stewarding the environment and slowing climate change.
Intergovernmental Panel on Climate Change. (2014). Climate Change 2014–Impacts, Adaptation and Vulnerability: Regional Aspects. Cambridge University Press
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.
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.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.
Vermeulen, S. J., Campbell, B. M., & Ingram, J. S. (2012). Climate change and food systems. Annual Review of Environment and Resources, 37.
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.[i]
Under a business as usual scenario modeled by researchers, in which global meat and dairy consumption continues to increase, emissions from food production alone (including emissions associated with land-use change, such as deforestation) would nearly exhaust the emissions budget in 2050 set for having at least a 66 percent chance of keeping global warming below 2° C.[ii] [iii] Consequently, combined with non‐agricultural sectors, global emissions would increase the likelihood of severe consequences for people, public health, economies, and ecosystems.
Food system activities, including producing, transporting and disposing of food, generate up to 30 percent of total global greenhouse gas (GHG) emissions.[iv] [v] Of these sources, livestock production is the largest, accounting for an estimated 14.5 percent of global GHG emissions from human activities, according to the United Nations.[vi] Meat and dairy from ruminant animals, such as cattle and goats, are particularly emissions-intensive.[vii]
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.
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).
Tilman, D., & Clark, M. (2014). Global diets link environmental sustainability and human health. Nature, 515(7528), 518-522.
Gustavsson, J., Cederberg, C., Sonesson, U., Van Otterdijk, R., & Meybeck, A. (2011). Global food losses and food waste (pp. 1-38). Rome: FAO.
Food and Agriculture Organization of the United Nations (2013). Food Wastage Footprint: Impacts on Natural Resources. Rome: FAO.
Globally about 30 percent of the food supply is never eaten.[viii] If all the world’s food losses and waste were represented as a country, that “country” would be the third highest greenhouse gas (GHG) emitter, after China and the US.[ix] Discarding food is akin to discarding all the embodied GHG emissions involved in its production, processing, transportation, cold storage, and preparation. Additionally, when food decomposes in landfills, it generates significant quantities of methane, a GHG that is up to 84 times more potent than carbon dioxide.[x]
The United Nations Sustainable Development Goal 12.3 calls for cutting wasted food in half by 2030.[xi] The United States Environmental Protection Agency and US Department of Agriculture have set the same goal.[xii] 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.
According to estimates by climate scientists, meeting this goal alone can reduce projected food production-related carbon dioxide equivalents by 22 percent in 2050.[xiii]
Dramatic reductions in meat and dairy consumption in high-consuming populations, alongside reductions in wasted food, are crucial for avoiding the most catastrophic climate change scenarios. Achieving this goal requires a nuanced approach to food system emissions mitigation strategies. Demand-side mitigation strategies should result in a reduction in the global average consumption of animal-based foods from projected amounts, with a particular emphasis on reductions among populations that already consume above-average amounts of animal-based foods.
Lipinski, B., O’Connor, C., and Hanson, C. (2016). SDG Target 12.3 on Food Loss and Waste: 2016 Progress Report. Champions 12.3. Retrieved from here.
United States Department of Agriculture (2015). Press release: USDA and EPA join private sector charitable organizations to set nation’s first food waste reduction goals. Retrieved from here.
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.
Additional studies that have demonstrated the need for dietary shifts to mitigate climate change:
A carbon footprint is a measure of how much a product or service—such as a head of chard, a slice of cheese, or a flight from Chicago to Chattanooga—contributes to the greenhouse gas emissions that warm the planet. For most foods, the largest share of greenhouse gas emissions comes from sources on the farm, such as animal manure or chemical fertilizers. Other sources include processing, transporting and preparing food, generating power for the stores that sell food, and decomposing food in landfills. Although the word “carbon” in carbon footprint refers to carbon dioxide, the term “carbon footprint” is often used to include other important greenhouse gases such as methane and nitrous oxide, both of which are associated with farming activities. Another term to use instead of carbon footprint is “greenhouse gas footprint,” which more clearly conveys that we should focus on more than just carbon!
Supply chains account for 18% of food emissions (…) Whilst supply chain emissions may seem high, at 18%, it’s essential for reducing emissions by preventing food waste. Food waste emissions are large: one-quarter of emissions (3.3 billion tonnes of CO2eq) from food production ends up as wastage either from supply chain losses or consumers.
Our society’s development of centralized food processing can reduce carbon emissions, and using food packaging can also help with reduction by preserving food, extending shelf life, and thus preventing food waste. But some aspects of our current food consumption practices in many countries contribute to high levels of carbon emissions and other adverse environmental impacts, such as long-distance transport in globalized food supply chains, convenience and highly processed foods, non-seasonal products, single-use food packaging and increased meat production. Therefore, to understand the impact of food processing and food packaging on carbon emissions, it is necessary to assess the full life cycle of food products in detail, including their supply chains, and packaging materials. In general, the fewest carbon emissions are generated through ensuring seasonal food production, local processing and local consumption, and using returnable and durable food packaging materials.
It can be better, but context matters. If local means seasonal, there can be an advantage to eating local produce grown in its natural season as this is likely to require low energy inputs for both production and transportation. However consider a scenario such as one that involved a study of tomatoes purchased in England in the winter that came from a local greenhouse (requiring extensive inputs for production in the cold weather), vs Spain at a time in the winter when tomatoes were still growing in the sun without the need for additional production inputs, and were shipped to England by boat in an energy efficient manner. The study reported a net benefit from overall production and transportation inputs for the tomatoes shipped from Spain vs. the “local” English tomatoes. Yes, local can be better, but context matters, and in general the production inputs for growing food outweigh transportation inputs.
Ultimately, changing the types of foods people eat and how those foods are produced and used is better for the climate than reducing the distances foods travel. Although it varies, depending on the product, transport is a small contributor to emissions. For most food products, it accounts for less than 10% of total food related emissions.
The authors of the UK study above estimated that avoiding air-freighted and hothouse-grown foods could reduce dietary GHG emissions by 5 percent—compared with a 35 percent reduction from eliminating meat from diets. Another study from the US found that avoiding red meat and dairy one day a week reduces GHG emissions more than eating locally every day. So, choosing local food has many advantages, but it is not the only solution for reducing the climate impact of our food.
Weber CL, Matthews HS. Food-miles and the relative climate impacts of food choices in the United States. Environ Sci Technol. 2008; 42(10).
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
The global food system is the second-largest GHG emitter, accounting for 26% of total GHGE. In 10-20 years-time, when fossil fuel is replaced by renewable energy sources, food systems will become the first contributor to GHGE. The production stage (livestock and crop production as well as land use) releases 80% of food-related GHG. One-quarter of this amount is wasted during food processing, transport, packaging, retail and consumption.
Greenhouse gas emissions from livestock are responsible for approximately 20% of current temperature increases. Beef cattle have a particularly significant impact due to their methane emissions and high land use. But unlike continuing to burn fossil fuels, we can envisage a certain level of beef production that could be compatible with stable temperatures. This, however, will require a shift to more sustainable farming, and a change in course from current trends, which would likely take the level of beef production beyond sustainable limits.
From a purely “size of environmental impacts and land use perspective”, eating chicken is better than eating beef for reducing climate change.
However as both chicken and beef are animals, they are more resource-intensive and environmentally impactful to produce than plant-based foods. Chicken requires three times more land and emits three times more greenhouse gas emissions than common plant-based protein sources such as beans, peas and lentils. While beef production typically requires 20 times more land and emits 20 times more greenhouse gas emissions per unit of edible protein than common plant-based protein sources. Yet even the most environmentally damaging production methods for chicken are lower carbon impact than the majority of the world beef production. This means that generally, If you want a lower-carbon diet, eating less meat is nearly always better than eating even the most sustainable meat. This is a complicated issue, and lower carbon is only one part of it. When choosing between beef, chicken and other sources of protein, you might want to also think about issues such as animal welfare, soil health, biodiversity, local economic impacts, and your dairy consumption (with milk production linked to some beef or veal production) to name but few interrelated issues.
Compared to most animal foods, plant foods generally require much less land and fresh water to produce, and have a much smaller impact on climate change and water pollution. There are exceptions of course, and there is room on sustainable menus for a small amount of animal foods. Well-managed grazing livestock, for example, can build fertile soil and make use of land that is too hilly or rocky for growing crops, while animals lower on the food chain such as insects, bivalve mollusks (e.g., oysters), and small fish (e.g., anchovies and sardines) have minimal impacts on the environment. A diet that is mostly plants with a small amount of these low food chain animal foods could lower a person’s food-related greenhouse gas and freshwater footprint by as much as 68% and 22%, respectively—almost as much as adopting an exclusively plant-based (vegan) diet.
Pound for pound, lamb, beef, cheese, and pork (in that order) generate the most greenhouse gases. When measured in terms of GHG emissions by gram of protein, dairy still lands in 3rd place in terms of climate impacts. Dairy products have large climate impacts because cows emit large quantities of methane through their unique digestive process (called enteric fermentation) and from their manure. Over a 20 year time frame, methane generates 80 times more warming gases than carbon dioxide and globally, dairy production generates 30% of all livestock emissions. Feed for dairy cows also generates significant quantities of nitrous oxide (a GHG that is 298 times more powerful than CO2). Among dairy products, milk and yogurt have the lowest carbon footprint and cheese has the highest because it takes roughly 10 pounds of milk to make 1 pound of cheese.
“Rice (Oryza sativa) is a staple for nearly one-half of the world’s seven billion people (1) and thus deserves special attention with respect to interactions with a changing climate. Rice farming provides a livelihood to ∼145 million households (1), who in turn utilize for 11% of arable land, one-third of irrigation water (1), and at least one-seventh of fertilizers globally (2). Rice cultivation results in enhanced methane (CH4) and nitrous oxide (N2O) emissions (hereafter, rice-CH4 and rice-N2O, respectively), both potent greenhouse gases (GHGs) that contribute to climate change.”
When excess nitrogen fertilizers (like urea) are added to soils to support plant growth, naturally occurring microbes in the soil generate nitrous oxide, a heat trapping gas 300 times more powerful than carbon dioxide. In fact, cultivation of all plants produces some nitrous oxide. Rice happens to be the crop which produces most climate pollution per unit calorie because, in addition to nitrous oxide, rice farms produce another heat-trapping gas called methane which is 80 times more potent than carbon dioxide. The presence of standing water at rice farms leads to lack of oxygen in soil and decomposition of biological matter which creates methane. The good news is that when the water levels at rice farms are managed stay within 5 cm (2 inches) of soil level and fertilizer addition is closely matched to the actual needs of the rice plant, total climate pollution from rice cultivation can be reduced by half.
Wasting food has a shockingly large carbon footprint. In fact, if global food waste were a country, it would be the third-highest GHG emitter after the U.S. and China, amounting to 8% of global greenhouse gas emissions. It’s latest edition, Project Drawdown ranked reducing food waste as the number one climate solution of 76 analyzed. Why so big, you may ask? Producing food has a huge footprint, especially when you consider meat production and the nitrous oxide emissions associated with fertilizer use. And after its produced, it must be transported, cooled, stored and cooked, all of which require significant energy. So when that half-pan of steak gets thrown out after the conference lunch, it throws out a whole lot of emissions with it. The good news is that it’s one of the more solvable problems out there and according to the IPCC, reducing food waste can not only help mitigate climate change, but also help adapt to some of the food shortages that are expected because of it.
The foods that are the greatest contributors to climate change are beef and lamb. This is because the grain used to feed animals is most often grown with large amounts of pesticides and fertilizer, which require fossil fuels to produce. These animals are ruminants, which means that when they eat these grains, their multi-chambered stomachs produce methane – a powerful climate polluter that is 80 times more powerful than carbon dioxide. The manure that they produce after digesting the grain also emits greenhouse gases. Finally, deforestation and other of clearing of land to make way for cattle-grazing can also result in more climate pollution. In all, beef is about five times more GHG-intensive as chicken and 34 times more GHG-intensive as legumes like beans and lentils, pound for pound. Beyond beef and lamb, animals and animal products are more climate-intensive than plants. In fact, producing the animals and animal products we eat causes as much climate pollution as all the tailpipe emissions from the world’s vehicles combined.
Cutting back on meat is one of the simplest changes someone can make in their diet, and even small reductions can have a meaningful impact on climate change, particularly when combined with the actions of other people around the world. The Meatless Monday movement, which has spread to over 40 countries, is a powerful example of the individual and collective impact of a shift towards a plant-based diet. If one person in the US goes Meatless Monday for a year, the amount of emissions saved is equivalent to driving 348 miles by car. If everyone in the US skipped meat one day a week, it would be the equivalent of 109 billion miles, which is a 6% reduction in diet-related GHG emissions! So by reducing meat in their own diet, then getting their family, friends and local institutions on board, an individual can make a big difference in the fight against climate change.
You don’t need to stop eating meat, but many of us should eat a lot less meat and be careful to choose meat raised as part of a regenerative system. People choose to limit their consumption of animal based products because of their impact on the climate and environment, some do it out of personal health concerns and some do it for animal welfare reasons. But it is important to recognize as well, that many people around the world especially young children in places where undernutrition is prevalent, need animal protein to meet their protein requirements for growth and health. Furthermore, animals are an integral part of a regenerative system, rotating grazing with crop production. Their waste, containing phosphorous and nitrogen, is a very necessary ingredient in building healthy soils and ensuring plant growth.