Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


Is becoming vegan the best thing people can do to reduce Greenhouse Gas emissions?

Posted on 19 March 2020 by Justine_Wickman

This is the new Advanced Rebuttal to the myth 'veganism is the best way to reduce carbon emissions' with the short URL 

Animal agriculture and GHG emissions

It has been estimated that 11-15% of human caused greenhouse gas emissions are a result of animal agriculture and livestock globally (FAO 2013.; Climate watch 2018). These gases include methane from enteric fermentation of cattle, nitrous oxide mainly from manure and carbon dioxide. The levels of each that are contributed vary depending on geographical location and the source of meat. Animal agriculture also uses vast amounts of other resources like land, fertilizer, feed and water, for example 8% of global water usage is taken up by livestock (Schlink 2010).  

Figure 1: Global human caused GHG emissions divided by sector as estimated by the Center for Climate and Energy Solutions 2013

A film by Kip Anderson; ‘Cowspiracy: The Sustainability Secret (2014)’ rallied for veganism as being the best way to reduce GHG emissions with claims that it is the ‘solution to climate change, to stop eating animals’ and ‘the only way to sustainably and ethically live on this planet with seven billion other people is to live an entirely plant-based vegan diet.’ This message was backed up by unreliable sources, for example quoting work by Goodland (2009) that animal agriculture is responsible for 51% of GHG emissions, when it has been estimated to be 11-15% (FAO 2013., Climate watch 2018). Although veganism does have the potential to reduce GHG emissions associated with diet, it is important to consider other sectors that are also part of the problem.

Are people willing to change their diets for the environment? 

Graça et al. (2015) showed that 60% of people have intention to change the amount of meat they consume; however, only 48.8% are actually willing to reduce their meat intake and only 44.4% are willing to completely change to a plant-based diet. Compared to other dietary changes people are willing to make to advantage the environment, only 46.9% of people are reducing their meat intake compared to 67.7% buying regional food and 62.9% eating seasonal fruit and vegetables (Tobler et al. 2011).

Eating meat is also perceived to have the least environmental impact compared to produce with excess packaging or inorganic and imported produce.  This suggests that many people may not be willing to eat a plant-based diet because they do not perceive eating meat to be a large environmental issue. Global veganism would require a mass change in mindset; people that show an attachment to meat are unlikely to respond well when faced with direct approaches to try and elicit change as they will react in a defensive manner (Graça 2015). Films such as Cowspiracy may not be the most productive way to encourage reduced meat intake and may have the opposite effect of making them firmer in their reasons for eating meat (Graça 2015).  

Figure 2: Willingness and intent of people to switch to a plant based diet using data taken from Graça et al. (2015)  

Problems with the vegan diet 

About one-third of all food grown is lost as waste, during transport and processing as well as at the retailer and consumer level (Gustavsson et al. 2011). Food waste is a contributor to food related GHG emissions (Scarborough 2014). Fruit and vegetables make up 39% of food waste with dairy and meat making up 17% and 14% respectively (Conrad et al. 2018). It is currently estimated that 4.2 trillion gallons of irrigation water and 780 million pounds of pesticides are depleted as a result of food losses and waste, most of which are used to produce fruit and vegetables (Conrad et al. 2018). With an increase in fruit and vegetable intake with a rise in vegan diets, the contribution of fruit and vegetable waste to GHG emissions and other depleted resources is likely to rise.

The large contribution of this waste attributed to fruit and vegetables is a result of retailer grading on its appearance due to the consumer avoiding disfigured produce. In an attempt to reduce the environmental burden of food, a reduction in the amount of waste on an individual level, specifically fruit and vegetables, is necessary, particularly if there is an increasing amount of these high-waste products due to more people switching to a vegan diet. 

Figure 3: Proportion of waste attributed to different food groups by US consumers. Other comprises of groups all with a percentage of <10% including: candy, soft drinks, salty snacks, soup, potatoes and mixed potato dishes, nuts and seeds, Mexican dishes, eggs and mixed egg dishes, table oils and salad dressing. Data taken from Conrad et al. (2018)

Carlsson-Kanyama (2009) showed that, ‘foods that commonly have low emissions, such as fruits, when they are transported by air, may have emissions as large as some types of meat.’ For example, domestic pork and chicken generate 9.3 and 4.3 kg of CO2-equivalent per kg of product, respectively, whereas fresh tropical fruit transported by plane generates 11 kg CO2-equivalent per kg of product. Therefore, although eating a vegan diet has the potential to reduce emissions, other types of foods that also have a large environmental impact should be reduced, which are not necessarily facilitated by a vegan diet.  Heller (2013) noted the environmental impact of vegetables produced in heated greenhouses can be greater than animal-derived products, showing that it is important to think about the farming and transportation of all produce, reducing intake of out-of-season and tropical produce, not just livestock, to reduce the environmental impact of a diet. 

Land management strategies are an important factor to consider when trying to mitigate some of the emissions associated with growing fruit and vegetables. Zomer (2017) claim that "land management strategies can increase soil carbon stocks on agricultural lands with practises including addition of organic manures, cover cropping, mulching, conservation tillage, fertility management and rotational grazing." The importance of this, as highlighted by Zomer (2017), is that mismanaged land can release carbon from topsoil into the atmosphere, with as estimated 50-70% of carbon soil stocks already lost in cultivated soils. Regard for the use of sustainable land management strategies with the increase in demand for non-meat produce that comes alongside veganism would be important; however, these management strategies, such as rotational grazing and organic manures, require livestock and therefore do not fit with a vegan diet. Perhaps rather than full veganism, it is necessary to consider a balance of sustainably-produced food using the land management strategies suggested by Zomer (2017)

Vegan vs. Vegetarian vs. meat diets

A vegan diet can reduce GHG emissions by 26% compared to the average meat-eating UK diet and a vegetarian diet could see a 22% reduction (Berners-Lee 2012; Saxe 2013; Scarborough 2014). Recent research by Kim et al. (2019) compared a flexitarian two-thirds vegan diet (which involved eating vegan for 2 meals per day and no restrictions on the third meal) to a fully vegetarian diet and found that in 95% of countries studied, the two-thirds diet produced less GHG emissions than the vegetarian diet.  Therefore, there are arguments that a flexitarian diet with moderate amounts of meat is better than a vegetarian diet that cuts out meat completely, showing that stopping meat intake completely does not necessarily reduce dietary GHG emissions and cannot be assumed to do so in a vegan diet. 

What are the alternatives?

Increasing understanding of livestock emissions may mean there is potential to partially mitigate the high levels of GHG emissions associated with livestock, without abandoning livestock production. For example, adding fumaric acid to goat feed has shown to reduce their methane production by 18-31% (Li 2018). However, this additive has been less successful in cattle, the largest culprits of methane gas production. Alternatively, adding seaweed (Asparagopsis armata) to the diet of dairy cow can reduce methane emissions by up to 67% (Roque et al. 2019)

Global veganism has the potential to reduce global GHG emissions; however, it is not the only option and may not be the most achievable. A combination of moderated red meat, lamb, and dairy intake along with sustainable farming techniques and locally-sourced produce to avoid airfreight would have a positive impact on the environment. However, it is important not to overemphasize one source of GHG emissions, for example livestock, as it can distract from the need to reduce human-caused emissions across a range of sectors. Films like ‘Cowspiracy’ that oversimplify the problem in order to advocate a single policy outcome may be similarly counterproductive as films that deny the problem in the first place.

Related research

Recent work by Allen et al. 2018 has highlighted that standardised measures of greenhouse gases such as GWP100 or GWP 20 can debated as to whether they represent accurate measurement of methane and its effects which may be may be overstated with these metrics. A future blog post discussing this is in the works. 



Allen, MR., Shine, KP., Fuglestvedt, JS., Millar, RJ., Cain, M., Frame, DJ., Macey, AH. (2018). A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation. Npj Climate and Atmospheric Science, 1:16. [Online].

Berners-Lee, M., Hoolohan, C., Cammack, H., Hewitt, CN. (2012). The relative greenhouse gas impacts of realistic dietary choices. Energy Policy, 43, 184-190. 

Carlsson-Kanyama, A., González, AD. (2009). Potential contributions of food consumption patterns to climate change. The American Journal of Clinical Nutrition, 89(5), 1704-1709. 

Climate Watch (2018). [Online] Avaliable at:

Conrad, Z., Niles, MT., Neher, DA., Roy, ED., Tichenor, NE., Jahns, L. (2018). Relationship between food waste, diet quality and environmental sustainability. Plos One. [Online].

Gerber, P., Steinfield, H., Henderson, B., Mottet, A., Opio, C., Dijkman, J., Falcucci, A., Tempio, G. (2013). Tackling Climate change through livestock: a global assessment of emissions and mitigation opportunities. FAO, Rome. 

Goodland, R., Anhang, J. (2009). Livestock and Climate Change: What is the key actors in climate change are cows, pigs, and chickens? World Watch. [Online].

Graça, J., Abílio, O., Calheiros, MM. (2015). Meat, beyond the plate. Data driven hypotheses for understanding consumer willingness to adopt a more plant-based diet. Appetite, 90, 80-90. 

Graça, J., Calheiros MM., Oliveira, A. (2015) Attached to meat? (Un)Willigness and intentions to adopt a more plant-based diet. Appetite, 95, 113-125. 

Gustavsson, J., Cederberg, C., Sonesson, U. (2011). Global Food Losses and Food Waste. Rome: FAO. 

Heller, MC., Keoleian, GA., Willett, WC. (2013). Toward a life cycle-based, diet-level framework for food environment impact and nutritional quality assessment: A critical review. Environmental Science and Technology, 47, 12632-12647.

Kim,BF., Santo, RE., Scatterday, AP., Fry, JP. Synk, CM., et al. (2019). Country-specific dietary shifts to mitigate climate and water crisis. Global Environmental Change. [Online]. 

Li, Z., Liu, N., Coa, Y., Jin, C., Li, F., Cai, C., Yao, J. (2018). Effects of fumaric acid supplementation on methane production and rumen fermentation in goats fed diets varying in forage and concentrate particle size. Journal of Animal Science and Biotechnology, 9(21). 

Roque, BM., Slawn, JK., Kinely, R., Kebreab, E. (2019) Inclusion of Asparagopsis armada in lactating dairy cows' diet reduces enteric methane emission by over 50 percent. Journal of Cleaner Production, 234, 132-138. 

Saxe, H., Larsen, TM., Mogensen, L. (2013). The Global warming potential of two healthy Nordic diets compared with the average Danish diet. Climate Change, 116, 249-262. 

Scarborough, P., Appleby, PN., Mizdrak, A., Briggs, ADM., Travis, RC., et al. (2014). Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK. Climate Change, 125, 179-192. 

Schlink, AC., Viljoen, GJ. (2010). Water requirements for livestock production: a global perspective. Scientific and Technical Review of the Office International des Epizooties, 29(3), 603-619. 

Tobler, C., Visschers, VHM., Siegrist, M. (2011). Eating Green. Consumers’ willingness to adopt ecological food consumption behaviours. Appetite, 57, 674-682. 

Zomer, RJ., Bossio, DA., Sommer, R. Verchot, LV. (2017). Global sequestration potential of increased organic carbon in cropland soils. Scientific Reports, 7(15554) [Online]. 

0 0

Printable Version  |  Link to this page


Comments 1 to 12:

  1. So, this article is posted on April 19, 2020? Back from the future?

    0 0
    Moderator Response:

    [DB] Fixed.

  2. A summary statement, with the full story presented above to help justify it, would be:

    People need to expand their awareness and improve their understanidng and apply what they learn to correct what has developed and help develop sustainable improvements for the future of humanity, especially learning what type of leadership to vote for.

    A great starting point would be the understanding that is the basis for the full set of Sustainable Development Goals. In addition to the above information are the understanding that:

    • the human body only extracts protein from 100 grams of meat in a meal (the rest of that 8 oz steak is waste, except for the taste)
    • humans do not need to eat 100 grams of meat in every meal

    That makes it undeniable that the most fortunate on the planet have a lot of opportunity to reduce how harmful and wasteful their diet, and their example, is. Correcting how they eat would make them Helpful Examples for everyone else to aspire to enjoy, and make them deserving of being higher status people.

    And that simple correction of how the richest eat can make a massive difference to many important issues, not just on the climate change front.

    A side issue is the need to stop the animal growing activity that is causing the frequent harmful contamination of produce like romaine lettuce.

    0 0
  3. The average sedentary male only needs 56 grams of protein a day, the average sedentary woman is 46 grams discussed here! Several credible websites I looked at had these or very similar numbers. This is much less protein than people typically consume in western countries.

    That said, I agree with the article that veganism doesn't appear a justified response to the climate issue. For example low density open grasslands cattle farming appears to be carbon neutral or even sequesters carbon, and has never to my knowledge caused a global warming problem in the historical past. The problem appears to be the rapid growth of high density cattle farming in the last 50 years or so generating a lot of methane. IIt all suggests lower meat consumption is wise, but not zero meat consumption.

    0 0
  4. 56gm/day is what is needed so you dont fall ill from defiency. A lot more is needed to maintain good health and adequate muscle-mass especially as you age.

    0 0

  5. How much would becoming everyone becomming vegan reduce Greenhouse Gas emissions? Most likely none, but at best maybe 5%.

    However, that’s not the full story because many ecosystems that could mitigate global warming are currently under the plow in order to provide feed for the most inefficient agricultural system we humans have yet to devise, factory farming of animals. When you include this destruction of ecosystem services on land primarily used to grow commodity grains for factory farms and biofuels, the number jumps to about 15%- 20% reduction in emissions and even more considering lost ecosystem services due to land use change.

    So at first glance it may seem like a great idea just to eliminate all domestic animal production and return those vast prairies back to the native grasses found before we plowed them up. The problem with this is that the grasses eventually become moribund and choke themselves out. They then either create huge grass fires or simply die.

    Walker et al. (1981) and Ruess (1987) and many more report that light grazing may stimulate grass growth, and lead to a higher biomass. This increase is probably due to the induction of tiller formation of perennial grasses (Tainton 1999). On the other hand, if grazing is too light, a significant amount of dry, moribund material may remain at the end of the season, causing the grasses to shade themselves.

    The importance of herbivory

    We could try burning that material. But that of course releases the CO2 and CH4 right back into the atmosphere, kills vast numbers of animals, and even can make a bad problem even worse. Don’t believe it? Ask Australia.

    fires with Kangaroo

    image courtesy New York Times

    What to Read on Australia’s Bushfire Crisis

    So you see it is entirely possible to both overgraze and to undergraze. Both cause ecological damages. This is where the Vegan argument breaks down. Here is why:

    The vast herds of herbivores that once grazed worldwide are gone. In many cases like in Australia most are extinct and never coming back. In other cases remnants exist but it would be virtually impossible to bring back huge herds 10’s of millions strong.

    In 1871, an American soldier named George Anderson send a letter to his sweetheart describing a herd he saw in Kansas.

    “I am safe in calling this a single herd,” he wrote, “but it is impossible to approximate the millions that composed it. It took me six days on horseback to ride through it.”-George Anderson

    Buffalo Holocaust

    Can you even imagine a herd of wild bison like that roaming through say… Wichita, Kansas today? It could take days crossing major interstates connecting east with west. You think rush hour gridlock is bad. Try a week long traffic jam! That kind of numbers just isn’t possible even if we did stop growing corn and soy to feed animals and biofuels for cars.

    So since it is impossible for us to completely restore those vast wild herds, and it is also impossible to restore the prairies without removing old moribund material because the top successional grasses just die or burn. That leaves us with only one solution. We actually need domestic animals raised properly to restore the habitat. If we do that we can restore much needed hapitat for dozens of endangered species.

    Grassland Birds: Fostering Habitats Using Rotational Grazing

    “As the small trickle of results grows into an avalanche — as is now happening overseas — it will soon be realized that the animal is our farming partner and no practice and no knowledge which ignores this fact will contribute anything to human welfare or indeed will have any chance either of usefulness or of survival.” Sir Albert Howard

    However even that’s not the whole story, because far from causing AGW, animal production done properly can actually sequester vast amounts of carbon in the soil through the grasslands symbiosis networks.

    Global Cooling by Grassland Soils of the Geological Past and Near Future

    So amazingly a very significant problem suddenly becomes our biggest chance for a solution! All we need to do is change the way we raise those domestic animals, and instead of causing global warming, they could potentially reverse it!

    “The number one public enemy is the cow. But the number one tool that can save mankind is the cow. We need every cow we can get back out on the range. It is almost criminal to have them in feedlots which are inhumane, antisocial, and environmentally and economically unsound.” Allan Savory

    And it is not just cows either. Savannas, open woodlands, forests etc all need animal impact to function as healthy ecosystems. They too can be restored with domestic animals raised properly!

    "The pigs do that work (by rooting in the forest and that creates the temporary disturbance on the ground that allows germination for higher successional species.) And so it allows for those pigs to be not just pork chops, bacon, and that. But now they then become co-conspirators and fellow laborers in this great land healing ministry ... by fully respecting the pigness of the pig." Joel Salatin

    In fact there isn’t an ecosystem on the planet that doesn’t need animal impact in order to make it sustainable. This is important to understand if we are really trying to develop sustainable agriculture. The good news is there are new improved methods for every major food world wide! All we need to do is make the change.

    Can we reverse global warming?

    "Permaculture is a philosophy of working with, rather than against nature; of protracted & thoughtful observation rather than protracted & thoughtless labor; & of looking at plants & animals in all their functions, rather than treating any area as a single-product system." Bill Mollison

    Vegans are well meaning and I support their personal choices, but there is a much much better path forward that allows vegans to eat what they like and the rest of us to eat what we like, and both will mitigate Global Warming.

    0 0
  6. Scaddenp @4,

    "56gm/day is what is needed so you dont fall ill from defiency. A lot more is needed to maintain good health and adequate muscle-mass especially as you age."

    I'm not so sure. Read this reference its from NZ (coincidence). Only certain groups of people need more. 

    Maybe you are thinking sort of subconsciously that 56 grams or protein equals 56 grams of meat. A grilled steak at 135grams is only 35 grams of protein (which surprises me), so  you would need about one 150 grams steak a day which is fairly decent size, plus a bit of protein from vegetables and brown bread etc.

    But plenty of people currently eat more meat than this each day, with meat sometimes at every meal.

    That said, really low meat consumption and veganism doesn't ring true to me environmentally. Quite apart from what Red Baron says, eliminating grasslands for cropping or forests creates yet more loss of diversity and natural habitats in the natural world.

    0 0
  7. No, I was looking further down in your original healthline article. Since we dont eat a lot of meat, we recently checked our intake against CSIRO guidelines. 1.2g/kg was regarded as minimum for older adults.

    0 0
  8. The vast herds of herbivores that once grazed worldwide are gone. In many cases like in Australia most are extinct and never coming back. In other cases remnants exist but it would be virtually impossible to bring back huge herds 10’s of millions strong.

    I feel compelled to ask what herbivores are now extinct in Australia.I know we have more Kangaroos than when Captain cook landed.There are Water buffalo going out of control in the north and camels in the middle that became such a problem in 2013 the Government commisioned pros to cull out as many as possible by helicopter.Its too remote to transport live or proccessed meat.Donkey and wild horses are culled by fitting a tracking collar on one and calling it a judas then regular culls are undertaken leaving the Judas alone as they herd up.Just curious as to what is extinct I know wallabys are culled in Tasmania In the west we do Reds and Greys but no wallaby species

    0 0
  9. If everyone became a vegetarian, far less land would be needed for food production. I and my wife are semi vegetarians. We buy organic beef and turkey at Whole Foods (which is mostly locally produced) so we can occaisionaly have beef taccos and turkey meat loaf. I suspect we eat much less meat than most Americans. I'm very physically active at the age of 70 so I think some meat will help balance my diet- plus I like the taste of quality meat though not on a daily basis.

    Land no longer used for meat production could be restored to forest and "natural grasslands" which would sequester a great deal of carbon. I say all this though I'm admitedly a bit of a climate skeptic. At least I do have a very  low carbon footprint- small car, small house, don't buy much, don't fly in jets and I do think vegetarianism or the semi version is good for health and if everyone did it- there is no downside. We'd be a much healthier nation more likely to solve national problems.

    0 0
  10. @ 8 Duncan,

    Seasonal migration of marsupial megafauna in Pleistocene Sahul (Australia–New Guinea)

    There were of course many more kangaroo and wallaby species, but also Diprotodon optatum, Nototherium, and others which were analogous to the large migrating herds in Africa, Asia, N & S America.

    0 0
  11. Responding to Duncan @8, in addition to RedBaron's @10.

    In Yuval Noah Harari's book "Sapiens" he provides a very compelling explanation for what caused the extinction of the very large animals that used to roam Australia ... Homo Sapiens arrived.

    0 0
  12. "Figure 3: Other comprises ...  Mexican dishes ..."

    Mexican dishes!? Why Mexican? Why are Mexican dishes singled out? 

    Is this a disparaging comment on Mexican food? :) 

    0 0

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us