How to Save the World by Switching Diet?

IPCC (2019) Report on the Climate-Eco-Food-Agro Nexus

IPCC (2019) has just released its comprehensive report on the interactions between global warming, ecology, food security and agriculture nexus — CEFA Nexus.

First of all, with the trend of the growing population, feeding 10b people in 2050 would be very difficult, if not impossible, if all of us are keeping our current food consumption rate as in developed countries. Figure 1 shows the current situation of the over-consumption of various types of food on different continents. The orange circle represents health boundary, in other words, all those pies extend beyond the orange circle imply over-consumption. North America’s diet (the right top corner one) seems to be the most unsustainable as it overconsumes red meat by 538% (red pie), starchy vegetables by 71% (brown pie), eggs by 168% (grey pie), poultry by 134% (yellow pie) and dairy foods by 45% (blue pie).

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Figure 1 Current dietary patterns and intakes of food. Source: EAT-Lancet (2019)

Besides insufficient food supply, the report also warns about the impacts on climate change, ecology and health issues, etc if the food production, distribution, consumption, and food waste handling processes are not improved immediately. The most straightforward solution is, of course, a reduction of food consumption or population. But it is easier said than done and sometimes it is even a taboo.

The consumption of red meat and dairy, in particular, is detrimental to the environment, not only on its emission of carbon dioxide, but also its consumption of land and thus deforestation, as shown in Figures 2 and 3.

Figure 2 shows the greenhouse gas emissions per gram of protein, which indicates the overwhelmingly excessive emission rate of producing beef/mutton (221.63 gCO2e). It is almost 10 times more than producing rice.

Similarly, Figure 3 shows the land use per gram of protein, which also found that producing beef/mutton requires almost 50 times more land than producing rice. It can lead to faster deforestation.

IPCC (2019) reports that “Agriculture, Forestry and Other Land Use (AFOLU) activities accounted for around 13% of CO2, 44% of methane (CH4), and 82% of nitrous oxide (N2O) emissions from human activities globally during 2007–2016, representing 23% (12.0 +/- 3.0 GtCO2e yr-1) of total net anthropogenic emissions of GHGs.” Footnote [1] shows the global GHG emissions in 2017.

However, under the current capitalism setting, food supply, especially processed food, is highly oligopolised, and the quantity/quality of food consumption is dominantly determined by the purchasing power of the consumers, it is very difficult to have any substantial and significant reduction of food consumption simply by educational means or ethical urges.

So there are some considerations of imposing carbon taxes or giving incentives to eco-friendly agricultural practices (payment for ecosystem services) to help solve the problems of the CEFA Nexus. Yet, they can also be very controversial, especially when the required reduction rate of consumption is substantial. For more details, it is recommended to read Chapter 5 of the IPCC (2019).

How much do we need to cut our food consumption can we save the globe? This is the most fundamental and important question when asking people whether they would accept the cut. Recently, there are two detailed reports telling us the extents of reduction in consumption and their corresponding impacts on the environment, so that we can have more informed choices.

For example, IPCC (2019) categories the choices into 8 types of diet, as shown in Figure 4, namely (1) Vegan, (2) Vegetarian, (3) Flexitarian, (4) Healthy diet, (5) Fair and Frugal, (6) Pescetarian, (7) Climate carnivore, and (8) Mediterranean. Footnote [2] shows the detailed differences between the 8 types of diet.

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Figure 4 Mitigation potential on GHG of changing diets by 2050. Source: IPCC (2019)

Comparing Flexitarian diet and Climate carnivore diet, for example, it seems to be much easier to switch from the current Standard American Diet to Climate carnivore diet, as it only requires switching 75% of ruminant meat and dairy by other meat. In contrast, it would be much more difficult, I suppose, to ask people to switch to Flexitarian diet which requires replacing 75% of meat and dairy consumption by cereals and pulses. Yet, the mitigation effect of adopting Flexitarian diet is almost 50% better than Climate carnivore diet. If all of us switch to Vegan, then it can reduce almost 8GtCO2e emission per year!

Another proposal suggested by the Norway-based thinktank EAT and the British journal the Lancet is also ambitious. Sawa (2019) refers to the EAT-Lancet (2019) Report’s proposal of cutting red meat and sugar consumption by 50%, resulting in a daily ration of red meat at 7g (with an allowable range of 0–14g), allocating little more than two chicken breast fillets and three eggs every fortnight and two tins of tuna or 1.5 salmon fillets a week, 250g of full-fat milk products (milk, butter, yoghurt, cheese) per day.

Even though these proposals seem to be hard to be achieved, since more and more studies found that whole food plant-based diets are healthier, it may become one of the major incentives urging people to switch to more eco-friendly diets.

IPCC (2019) provides a chart (Figure 5 below) showing the reduction in relative risk (%) of Type II diabetes, Cancer, Coronary mortality and All-cause mortality associated with 3 types of diet, namely (1) Mediterranean, (2) Pescetarian, and (3) Vegetarian.

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Figure 5 reduction in relative risk (%) of Type II diabetes, Cancer, Coronary mortality and All-cause mortality associated with 3 types of diet, namely (1) Mediterranean, (2) Pescetarian, and (3) Vegetarian. Source: IPCC (2019)

The benefit of a Vegetarian diet on reducing Type II diabetes risk is eye-catching. It can cut almost 40% risk! Mediterranean diet is more powerful in reducing coronary mortality and all-cause mortality, while Pescetarian diet is performing the best in reducing the risk of cancer. Anyway, it seems to imply that all these more eco-friendly diets are healthier than our current Standard American Diet.

If you do not want to change your diet, you can still take simple actions to help. For example, it is quite easy for all of us to reduce food loss and food waste, without any troubles. The contributions can be huge because it is reported that combined food loss and waste amount to a third of global food production, accounting for 8–10% of total GHG emissions in 2010–2016; and cost about USD 1 trillion per year. Quantity-wise, global food loss and waste amounted to 1630 Mt in 2011. (IPCC, 2019) Eat less, don’t waste can immediately help save the globe and your wallet.

Furthermore, we can also exercise our consumers’ rights to buy more from farmers who practice eco-friendly farming practices and buy less from farmers who do harm to the environment and our health. It is because food production, the EAT report states, “is the largest source of environmental degradation” (Sawa, 2019). The Report puts forward 4 types of sustainable integrated agricultural systems, namely (1) agroecology, (2) climate smart agriculture, (3) conservation agriculture, and (4) sustainable intensification. When farmers use no artificial pesticides and can keep the soil healthier, we and the insects can avoid eating toxins and can have food of higher nutrient density. Protecting insects is protecting ourselves. There have been several large-scale studies this year reporting that our current common farming practices are killing insects and resulting in speedy extinction of organisms. (Diaz et al., 2019; Leahy, 2019; FAO, 2019)

You can also buy more from your local community farms rather than buying imported foods, or you can even start farming at home or at your communities to practice urban agriculture. It can save transportation cost and carbon emission.

Lastly, the Report provides a full list of response options for dealing with this CEFA Nexus, as extracted in Figure 6, for you to choose. There must be some actions that fit you.

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Figure 6 Response options related to food system and their potential impacts on mitigation and adaptation. Source: IPCC (2019)


[1] Total annual greenhouse gases emissions, including from land-use change, reached a record high of 53.5 GtCO2e in 2017. According to the UN’s (2018) estimation, global GHG emissions in 2030 need to be approximately 25 percent and 55 percent lower than in 2017 to put the world on a least-cost pathway to limiting global warming to 2 oC and 1.5 oC respectively. That means, it requires cutting about 13.4 GtCO2e and 29.4 GtCO2e respectively

[2] Vegan: Completely plant-based. Vegetarian: Grains, vegetables, fruits, sugars, oils, eggs and dairy, and generally at most one serving per month of meat or seafood. Flexitarian: 75% of meat and dairy replaced by cereals and pulses; at least 500 g per day fruits and vegetables; at least 100 g per day of plant-based protein sources; modest amounts of animal-based proteins and limited amounts of red meat (one portion per week), refined sugar (less than 5% of total energy), vegetable oils high in saturated fat, and starchy foods with relatively high glycaemic index. Healthy diet: Based on global dietary guidelines for consumption of red meat, sugar, fruits and vegetables, and total energy intake. Fair and Frugal: Global daily per-capita calorie intake of 2800 kcal/cap/day (11.7 MJ/cap/day), paired with relatively low level of animal products. Pescetarian: Vegetarian diet that includes seafood. Climate carnivore: 75% of ruminant meat and dairy replaced by other meat. Mediterranean: Vegetables, fruits, grains, sugars, oils, eggs, dairy, seafood, moderate amounts of poultry, pork, lamb and beef.


Diaz et al. (2019) Summary for policymakers of the global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, May 6. (IPBES 2019)

EAT-Lancet (2019) Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems, EAT-Lancet Commission, Jan 16.

FAO (2019) The State of the World’s Biodiversity for Food and Agriculture — in brief, FAO Commission on Genetic Resources for Food and Agriculture — Assessment, FAO, Full report at

IPCC (2019) Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems, IPCC August 2019.

Leahy, S. (2019) Insect ‘apocalypse’ in US driven by 50x increase in toxin pesticides, National Geography, Aug 6.

Sawa, D.B. (2019) Seeds, kale and red meat once a month — how to eat the diet that will save the world, The Guardian, Jan 17.

UN (2018) Emissions Gap Report 2018, COP24, Dec 5.

Written by

ecyY is the Founder of Real Estate Development and Building Research & Information Centre REDBRIC

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