Some people, like myself, made a conscious decision to exclude various animal products from their diets, believing that this is an inevitable requirement if our species intends to live on Earth sustainably in the numbers we exist today.

I am aware of the following ways how vegetarianism / veganism benefits the Earth and humans who inhabit it:

  1. it reduces our carbon footprint and contributes towards tackling the climate change.
  2. due to a significant energy loss when moving up the food chain (about 90% is lost), consuming the primary producers of food (photosynthesizing plants, algae, etc.) seems to be an effective way of solving the global food crisis, which is caused by a rapid growth of human population that consumes at an ever faster rate the limited resources of the Earth.
  3. it reduces the amount of pollution associated with livestock, such as air and water pollution. For example, agricultural runoff, among other things, causes eutrophication of water bodies and death of marine organisms. This can be viewed as a conservation and biodiversity issue.
  4. it reduces deforestation, because large areas of forests are being destroyed to grow crops that are eaten by livestock.
  5. it reduces soil erosion associated with overgrazing by cattle.
  6. it addresses the growing concern in increase of antibiotic-resistant strains of human pathogens, which is associated with the use of antibiotics for livestock, compromising its effectiveness for humans.

I want to answer the question whether practices of vegetariansim or veganism, if implemented by the majority of the world population, could conceivably have a significant and positive effect on the issues outlined above or even solve them altogether. I am particularly interested in evaluating the consequences that such a change might have -- are there any potential negatives in moving entirely to plant farming?

To avoid making your answer an opinion, let me suggest you to focus on existing surveys and modeling, or back-up your opinion with data.

  • Good question, and I agree, this question can be answered in a non-opinionated manner. I have also started towards a vegetarian diet, cutting about 90% of the met I used to have out of my diet. Health wise I am finding I am better off. – user1017 Jan 12 '14 at 7:50
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    @hortstu, is it a well-known fact? I'd be grateful if you linked it to us if you find the source. IPCC might have it somewhere in their report, I guess. The pitfall here is that some studies look at agriculture, which is not limited to livestock only, and thus doesn't answer our question. – Th334 Jan 12 '14 at 22:32
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    I paraphrased the question to specify that I'm looking for a balanced answer, and the potential negatives of such a global change should be also mentioned (I also added the antibiotics bit for our readers as additional background information). – Th334 Jan 12 '14 at 22:50
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    @hortstu, I actually found the very same statement in another article, and they referenced this publication by some body in the United Nations. It seem like a good read on our subject. – Th334 Jan 13 '14 at 5:40
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    Worth considering that not all livestock farming is the same - e.g. hill-farmed sheep in the UK use land that is unsuitable for crop growing. I have read research (though there is conflicting research) suggesting that grazed upland pasture sequesters more CO2 than if the same land was left to climax vegetation, so some lamb is actually carbon-neutral. Beef fed on soya from slash-and-burned rainforest would be a different story! Can't lay my hands on sources at the moment - will answer if I can. – aucuparia Apr 29 '15 at 11:44
up vote 9 down vote accepted

This is a partial answer, based on some research. Many web searches on this topic are difficult, as many sites have a bias one way or another. This answer will include names of researchers and links to articles when I can.

Note: a lot of articles are based on the American situation; however, these studies can be used as a 'measuring stick' for much of the meat-eating world.

Some statistics are presented in the article Sustainability of meat-based and plant-based diets and the environment. (Pimentel and Pimentel, 2003) stating that globally, as of about 2003:

  • About 2 billion people have a meat based diet, the remaining having a plant based diet, partly due to

shortages of cropland, fresh water, and energy

  • In a comparison (for the US), all food production was considered by the authors as being unsustainable - utilising 50% of the land, 80% of the fresh water and critically (according to the authors), 17% of the fossil fuels. However, having said that, when they compared

The use of land and energy resources devoted to an average meat-based diet compared with a lactoovovegetarian (plant-based) diet

comparing the resources required for the same amount of calorie intake, they found that

the lactoovovegetarian diet is more sustainable than the average American meat-based diet.

in terms of land and water use and fossil fuel requirements.

Further data is presented in the article How Does Meat in the Diet Take an Environmental Toll?, stating that studies by the Environmental Working Group indicated that

red meat such as beef and lamb is responsible for 10 to 40 times as many greenhouse gas emissions as common vegetables and grains.

Another critical point the article reported states is that

“If all the grain currently fed to livestock in the United States were consumed directly by people, the number of people who could be fed would be nearly 800 million,” reports ecologist David Pimentel of Cornell University’s College of Agriculture and Life Sciences.

I know that is a single country example, but it does provide an indication of statistically how a change to a vegetarian/vegan diet could be of benefit.

The article Diet and the environment: does what you eat matter? (Marlow et al. 2009), describes a key statisical measure, using California as an example:

or the combined differential production of 11 food items for which consumption differs among vegetarians and nonvegetarians, the nonvegetarian diet required 2.9 times more water, 2.5 times more primary energy, 13 times more fertilizer, and 1.4 times more pesticides than did the vegetarian diet.

A final global statistic (estimate) reported in the article UN urges global move to meat and dairy-free diet (Carus, 2010), states that a UN report determined that

Agriculture, particularly meat and dairy products, accounts for 70% of global freshwater consumption, 38% of the total land use and 19% of the world's greenhouse gas emissions.

TL:DR Given that statistically, many studies at local, state, national and global levels have shown that meat product agriculture is a major consumer of not only water and land, and not only are a significant contributor to environmental problems, they are also are a great consumer of grains that could be used as food.

However, many studies indicate that as modern agriculture is not all that sustainable, changes would be needed to be made to agricultural practices to make a global shift towards vegetarianism truly sustainable.

  • Thanks a lot for the data, it contributes to the topic big time. I still need to think whether my question is answered fully though. A question for you: when Marlow et al. (2009) mentioned "2.5 times more primary energy", did he refer to the solar energy, and if so, why is it only 2.5 times, whereas the food chain studies claim that ~90% of the energy is lost at each link. Secondly, as I mentioned before, citing numbers for agriculture doesn't really tell me anything about the impact of a vegetarian diet. – Th334 Jan 12 '14 at 23:42
  • No worries, I would imagine more complete answers will be forthcoming. In regards to your question, I think what Marlow et al were referring to was that the 'primary energy' is the energy supplied. – user1017 Jan 12 '14 at 23:47
  • Another bit of information from the Marlow et al paper is A positive return of 2–3 nutrient calories per calorie of primary energy input is characteristic for most cereal grains and legumes. Most fruit and vegetables return ≈0.5 calories, and animal products return ≈0.01–0.05 calories. The energy inputs for animal products may be 2.5–5.0 times greater than for plant products – user1017 Jan 12 '14 at 23:47
  • Thanks, but... it all makes perfect sense, until he says that meat's calorie efficiency is 2.5-5.0 times lower. If plants give 3 calories per calorie of primary energy, and meat gives 0.05 calories, it's like 60 times, no? Even if it's fruit with 0.5 calories, it's still at least 10 times more than meat, which is close to the common estimate of 90% energy loss. And why it's called energy input in the last sentence while it seems like an output? I know that it's not your paper, just in case you understand it better. – Th334 Jan 13 '14 at 4:00
  • @Herman true, the paper is not written the best - my understanding is that the energy input required for meat based agriculture is 2.5 to 5 times greater and the output is the 60 times greater that you identified. – user1017 Jan 13 '14 at 4:03

You must read The Vegetarian Myth by Lierre Kieth: http://www.bookdepository.com/Vegetarian-Myth-Lierre-Keith/9781604860801

It's an excellent book, well cited and rich in information, presenting a factual viewpoint that my vegetarian-of-17-years self had to stand up and take notice of. Such a complicated topic, this book really opened my eyes. Needless to say i am no longer a vegetarian.

Added By J. Cho: Excerpt:

[The book] exposes the destructive history of agriculture causing the devastation of prairies and forests, driving countless species extinct, altering the climate, and destroying the topsoil and asserts that, in order to save the planet, food must come from within living communities. In order for this to happen, the argument champions eating locally and sustainably and encourages those with the resources to grow their own food. Further examining the question of what to eat from the perspective of both human and environmental health, the account goes beyond health choices and discusses potential moral issues from eating or not eating animals. Through the deeply personal narrative of someone who practiced veganism for 20 years, this unique exploration also discusses alternatives to industrial farming, reveals the risks of a vegan diet, and explains why animals belong on ecologically sound farms."

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    Hello Natalie, and welcome to the site. What we're doing here is building an awesome body of questions and answers. While great answers may contain links to references, they really do need to stand alone and be self-contained too. Please can you edit your answer to include a summary of the relevant bits of the book that apply to the question as asked? It doesn't need to be an essay - just a dozen sentences or so that summarise the book's key arguments that directly apply to the question at the top of this page. – EnergyNumbers Aug 3 '14 at 18:33

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