Which meat is worse for the climate?

With 7.7 billion people on Earth [1] we have to produce a lot of food. Sadly, food production is a major source of greenhouse gas emissions [7,9,10] and the main cause of tropical deforestation [5]. But we do need to eat! So what foods are better and worse for the planet?

Swipe across for a graph showing CO2e* emissions per 100 grams of protein of various food types [2]. The lines span from the lowest 10% to the highest 10% of emissions for that food, indicating how emissions vary depending on how the food is made [2].

Keep in mind that different foods have different nutritional qualities [18]. Root vegetables may cause very low CO2e emissions [2], but we can’t only eat root veg…

What can we learn from this? Fruit, vegetables, and cereals have very low emissions [2]. The most efficient sources of protein are also plant-based [2]! Beef and lamb have comparably very high emissions [2] because cows and sheep burp lots of methane [9,10], a potent greenhouse gas [13].

Strikingly, chicken produces on average only 10% as much CO2e emissions as beef (per gram of protein) [19]. More people eating chicken (instead of beef) would make more chickens suffer [20]: farmed chickens often have very poor welfare [23,24]. For example, chickens may behave abnormally, be chronically hungry [25], or die from disease [26]. On the other hand, it would save land from deforestation [2], saving wildlife [22], and reducing emissions [2].

Whilst it would be ideal if we all ate diets with a minimal environmental impact, including no meat [2], this is unlikely to happen [21]. Therefore, if we all stopped eating red meat, this would be better for the planet than 10% of us going vegan.

*To measure the impact of different greenhouse gases in one unit, scientists invented “CO2 equivalent (CO2e)” [11]. 1kg of methane emissions is 28kg CO2e

References

[1] http://worldpopulationreview.com/

[2] https://science.sciencemag.org/content/360/6392/987

[3] https://link.springer.com/article/10.1023/A:1025593121839

[4] https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf

[5] https://www.rainforest-alliance.org/issues/food

[6] https://www.sciencedirect.com/science/article/abs/pii/S0168159106002954

[7] https://www.canr.msu.edu/resources/management_of_nitrogen_fertilizer_to_reduce_nitrous_oxide_emissions_from_fi

[8] http://www.fao.org/3/a-a1200e.pdf

[9] http://www.fao.org/news/story/en/item/197623/icode/

[10] https://climate.nasa.gov/faq/33/which-is-a-bigger-methane-source-cow-belching-or-cow-flatulence/

[11] https://www.esrl.noaa.gov/gmd/education/info_activities/pdfs/CTA_the_methane_cycle.pdf

[12] https://www.nature.com/articles/nature25785

[13] https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf

[14] https://books.google.co.uk/books?hl=en&lr=&id=fzc7CgAAQBAJ&oi=fnd&pg=PR3&dq=animal+welfare+poultry&ots=KhXOzGINP4&sig=HaKRTXY33ja8fdIo8rkI8Fa7rVw#v=onepage&q=animal%20welfare%20poultry&f=false

[15] https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.8837

[16] https://www.researchgate.net/profile/David_Wallinga/publication/255601050_Poultry_on_Antibiotics_Hazards_to_Human_Health/links/53fcc9ff0cf2364ccc04d650/Poultry-on-Antibiotics-Hazards-to-Human-Health.pdf

[17] https://www.nature.com/articles/35016500

[18] https://eatforum.org/content/uploads/2019/07/EAT-Lancet_Commission_Summary_Report.pdf

[19] Our calculations based on data S2 from Poore and Nemecek 2018: https://science.sciencemag.org/content/360/6392/987/tab-figures-data

[20] https://kb.rspca.org.au/knowledge-base/what-are-the-animal-welfare-issues-with-meat-chicken-farming/

[21] https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/resistance-to-changes-in-diet/D49ADDFD1766BE849886D7279EB89EBF

[22] https://www.nature.com/articles/nature01795

[23] https://www.sciencedirect.com/science/article/pii/S187114130700217X

[24] https://www.publish.csiro.au/an/pdf/AN15383

[25] https://www.cambridge.org/core/journals/world-s-poultry-science-journal/article/broiler-breeders-feed-restriction-and-welfare/F1077D49FA7F1A5D2122E5EA654FACC9

[26] https://www.sciencedirect.com/science/article/pii/S0167587718306044

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