Ancora Imparo

19 July 2007

Vegetarianism vs. Meat-Eating and Global Warming

Filed under: environment,global warming,science — Darmok @ 07:12 UTC

Those of you concerned about climate change may already know that one of the more significant changes an individual can make is to reduce the consumption of meat. In an article yesterday (“Meat is Murder on the Environment”), New Scientist reported on a study by Ogino and colleagues in this month’s Animal Science Journal that analyzes, in detail, beef’s environmental impact. It concludes

A kilogram of beef is responsible for more greenhouse gas emissions and other pollution than driving for 3 hours while leaving all the lights on back home.

(It should be noted that the three-hour drive is based on emissions from European cars; the fuel efficiency of American cars is much worse and so the equivalent driving time would be less in the United States.) The greenhouse gas emissions consist primarily of methane from the animals’ digestive systems. Also, transportation and production of the animals’ feed takes a significant amount of energy/fuel. Non-environmental harms—such as the the promotion of antibiotic resistance in humans by the use of (often preventitive) antibiotics in animals—were not considered.

Naturally, eating vegetarian food instead still will incur some of the energy costs, but in significantly reduced amounts. As energy flows through the food chain, a significant portion is lost at each step (90% is often cited). This suggests that it would take ten times the plant material to feed a herbivore to provide meat with equivalent energy yield as it would consuming the plants directly. That will require ten times more land to be used, use ten times more water and fertilizers, ten times more fuel for transport (not to mention the cost of transporting the meat, which was not included in the study), and so on. Producing meat requires between twenty-five and two hundred fifty times as much water as producing an equivalent amount of grain (estimates vary by study, but the ratio is probably closer to the higher end).

Other publications have discussed the tremendous environmental impact of meat consumption and the potential benefits of switching to plant consumption. In the 9 April 2007 issue of TIME (see also my previous post about this issue), Bryan Walsh wrote

If you switch to vegetarianism, you can shrink your carbon footprint by up to 1.5 tons of carbon dioxide a year, according to research by the University of Chicago. Trading a standard car for a hybrid cuts only about one ton—and isn’t as tasty.

And in March 2007, National Geographic had this to say:

If, like most Americans, you get close to 30 percent of your calories from meat, dairy, and poultry, your diet contributes over 3,274 pounds (1,485.1 kilograms) [of carbon dioxide emitted annually]. Vegetarian diets contribute half that, but you can also replace your calories from red meat with fish, eggs, and poultry, for savings of over 950 pounds (430.9 kilograms).

Of course, these studies tend to focus on switching from meat to a caloric equivalent of plant-derived food. In the developed world, though, obesity has reached epidemic proportions—in the United States, over three-fifths of adults are overweight, and over one-quarter are obese (source, CDC). The environmental benefit of simply eliminating some meat consumption and not replacing it with plant consumption would naturally be even higher than the alternative.

Finally, I must note that these benefits are not immediate. Forgoing that cheeseburger today will not reduce global warming tomorrow. Rather, as less meat is consumed, less livestock will be raised, and therefore cause less environmental harm over years and decades.

I’d summarize this as follows:

  • The consumption of meat (indirectly, in the form of production) results in a tremendous negative impact on the environment.
  • Switching to vegetarianism is probably one of the single most effective lifestyle changes an individual can make in mitigating global warming. However, even if one is not prepared for such a dramatic change, there are several intermediate changes that will also provide significant benefits.
  • Eliminating only mammals (beef, pork, and so on) from one’s diet has a major, beneficial impact.
  • Alternatively, cutting back on meat intake can also be quite beneficial. For instance, depending on one’s meat intake and desire, one could avoid meat one day a week, or perhaps half the week, or even only eat meat one day a week.
  • For those that are overweight or obese, reducing harm to the environment is one more reason to reduce food intake, especially that of meat.

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14 Comments

  1. [...] into our cows. I have not done the calculations, but I expect that much of the benefit in terms of our personal carbon footprint which might be gained by giving up beef altogether might also be gained by eating grass-fed beef. [...]

    Comment by A Modest Proposal: Cellulosic Beef « Alternative Energy Stocks — 30 July 2007 @ 09:13 UTC

  2. [...] Just back from a fresh crab and avocado salad in San Francisco, I was delighted to hear from Darmok and revisit his informative post on Vegetarianism vs. Meat-Eating and Global Warming. [...]

    Comment by Diet change helps climate change « inel — 23 August 2007 @ 12:25 UTC

  3. One side benefit of reducing feed production would be reducing the amount of nitrogen and phosphorus (largely from fertilizers) than enter our waterways. Some of our research found a shift away from feed cultivation could help solve the Gulf of Mexico hypoxia problem, which is driven in large part by fertilizer applied to crops grown for animal feed.

    Comment by Simon D. — 23 August 2007 @ 15:57 UTC

  4. Simon, you’re right, of course. Growing crops also has negative environmental impacts—though not nearly severe as those from raising livestock—and the increased amount of crops required to feed livestock (instead of humans) can be be expected to harm the environment in many ways.

    Comment by Darmok — 24 August 2007 @ 02:20 UTC

  5. Hello Darmok! Your timely summary of this topic has anticipated a paper in the Lancet, accessible via the Lancet series on Energy and Health. I am listening to the audio press conference right now. Here’s the paper, which I cannot read, but you may have access to:

    World meat consumption should be reduced by 10%: less meat means less heat
    Worldwide average meat consumption could be realistically reduced by 10% to reduce the already substantial impact of livestock production on greenhouse gas emissions. This would also reduce health risks associated with very high consumption of red meat. The fifth paper in the series entitled “Food, livestock production, energy, climate change, and health.” comments that the Global average meat consumption is currently 100g per person per day, with about a ten-fold variation between high-consuming and low-consuming populations. 90g per day is proposed as a working global target, shared more evenly, and with not more than 50g per day coming from red meat from ruminants (i.e., cattle, sheep, goats, and other digrastic grazers).

    Comment by inel — 13 September 2007 @ 20:31 UTC

  6. You’re right; this article is timely and apropos to my post. What an interesting series! I’ll write more when I get a chance to read through them.

    Comment by Darmok — 19 September 2007 @ 07:37 UTC

  7. I agree, there are certain benefits to reducing the consumption of meat or being a vegetarian. But I am not totally buying the data on adverse effects, you report, from meat consumption. If all turn into vegetarians there will be associated costs to the environment and to the economy. I am a vegetarian…FYI. I would like to read the actual journal articles to see the research done. Sometimes, magazines such as TIME, livescience filter facts. A peer reviewed journal findings is what I would go by in these type of assertions. All in all though, it is an important posting..great job!

    Comment by mridula — 9 October 2007 @ 05:11 UTC

  8. Mridula, you are correct that it is good to examine the original data. In my post I linked to the Ogino et al study that the New Scientist article discusses. Also, Inel’s comment (two above yours) has a link to an article in the Lancet, a prestigious medical journal, about the adverse environmental effects of raising livestock and such, and refers to several studies on the subject. Feel free to examine the data at your leisure.

    What sort of environmental cost do you envision if everyone were to become vegetarian? The crops required to feed vegetarians are much, much less than the crops required to feed enough animals to feed one who eats meat. (That, of course, is ignoring the environmental costs of raising the animals themselves.)

    Costs to the economy? Certainly, if everyone were to become vegetarian at once. But that is not realistic, nor is it what I am advocating. Any change has the potential to cause economic difficulties for those who follow the old path. Does restricting tobacco use hurt tobacco farmers? Certainly, but I consider that an insufficient reason to not advocate change. Besides, the economic impact of unmitigated global warming will do far more damage to the economy as a whole than declines in meat eating will do to the livestock industry.

    Comment by Darmok — 9 October 2007 @ 05:37 UTC

  9. [...] Ancora Imparo: Vegetarianism vs. Meat-Eating and Global Warming [...]

    Comment by Veggie Tuesday « the mindful mission — 12 February 2008 @ 10:21 UTC

  10. What is Google doing?? After this entire entry they go and place an AD FOR BEEF on this site. Mail order beef. Can you believe it? “Grass Fed Beef: steak, ribs, roasts, & burger. Our ranch, our cattle, in clean MT. Lacense…” Etc, etc. Google can map the Earth but can’t tailor ads? Weirdly creepy and insensitive if you ask me. Grazie per l’informazione!

    Comment by Marian — 28 February 2008 @ 05:06 UTC

  11. I’m glad you liked the entry!

    I think Google is tailoring the advertisements, in a way. I believe Google selects ads based on text within the page, and since I mention various meats in this entry, it supplied an advertisement that wanted to be featured in pages that discuss meat.

    Comment by Darmok — 28 February 2008 @ 06:47 UTC

  12. What many people fail to mention or realize is that one of the factors making people in this country sick and overweight is mass consumption of factory farmed meat. Factory farmed meat is by far in the majority, with real organic, natural, grass-fed varieties the exception. Studies have shown that people who consume moderate amounts of these types of meats versus the industrial variety are far healthier than those who choose the factory farmed versions or those on strict vegetarian and vegan diets. Also, grass-fed animals and those raised in a sustainable manner actually is beneficial to the environment. What is harming the environment so terribly is the persistence of factory farming. Read our article on Why Meat Gets The Heat at Agriculture Society (Google this article title on the search).

    Comment by AS — 30 May 2008 @ 04:25 UTC

  13. I’m no expert in these matters but I suggest many of you might want to review a few sites may enlighten you on many subject matters regarding energy and renewable. For example posted many articles on this.

    Comment by jack — 1 June 2008 @ 13:48 UTC

  14. If you are really interested in Alternative Energy you can also visit Ethanol Investments.

    Comment by Henry — 1 June 2008 @ 13:52 UTC


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