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Climate Hustle

How much does animal agriculture and eating meat contribute to global warming?

What the science says...

Animal agriculture is responsible for 1418% of human-caused greenhouse gas emissions globally, and less in developed countries (e.g. 6% in the USA).  Fossil fuel combustion for energy and transportation is responsible for approximately 60% of human-caused greenhouse gas emissions globally, and more in developed countries (e.g. 80% in the USA).

Climate Myth...

Animal agriculture and eating meat are the biggest causes of global warming
Becoming Vegan or cutting down on your own personal meat consumption could be the single most effective action that you can do to help reduce green house gas emissions.
Planet Earth Herald

The burning of fossil fuels for energy and animal agriculture are two of the biggest contributors to global warming, along with deforestation.  Globally, fossil fuel-based energy is responsible for about 60% of human greenhouse gas emissions, with deforestation at about 18%, and animal agriculture between 14% and 18% (estimates from the World Resources Institute, UN Food and Agriculture Organization, and Pitesky et al. 2009).

WRI global GHG emissions flowchart

Global human greenhouse gas emissions flowchart, from the World Resources Institute.

So, animal agriculture and meat consumption are significant contributors to global warming, but far less so than fossil fuel combustion.  Moreover, fossil fuels are an even bigger contributor to the problem in developed countries, which use more energy and have increased livestock production efficiency (Pitesky et al. 2009).  For example, in the United States, fossil fuel-based energy is responsible for about 80% of total greenhouse gas emissions as compared to about 6% from animal agriculture (estimates from the World Resources Institute and Pitesky et al. 2009).

US GHG emissions flowchart

US human greenhouse gas emissions flowchart, from the World Resources Institute.

How does animal agriculture cause global warming?

On of the main ways in which the livestock sector contributes to global warming is through deforestation caused by expansion of pasture land and arable land used to grow feedcrops.  Overall, animal agriculture is responsible for about 9% of human-caused carbon dioxide emissions globally (UN FAO).

Animal agriculture is also a significant source of other greenhouse gases.  For example, ruminant animals like cattle produce methane, which is a greenhouse gas about 20 times more potent than carbon dioxide.  The livestock sector is responsible for about 37% of human-caused methane emissions, and about 65% of human nitrous oxide emissions (mainly from manure), globally (UN FAO).

Beef is a bigger problem than other sources of meat

Producing beef requires significantly more resources (e.g. land, fertilizer, and water) than other sources of meat.  As ruminant animals, cattle also produce methane that other sources (e.g. pigs and chickens) don't.

Eschel et al. 2014 estimated that producing beef requires 28 times more land, 6 times more fertilizer and 11 times more water than producing pork or chicken.  As a result, the study estimated that producing beef releases 4 times more greenhouse gases than a calorie-equivalent amount of pork, and 5 times as much as an equivalent amount of poultry.

Eating vegetables produces lower greenhouse gas emissions yet.  For example, potatoes, rice, and broccoli produce approximately 3–5 times lower emissions than an equivalent mass of poultry and pork (Environmental Working Group 2011).  The reason is simple – it's more efficient to grow a crop and eat it than to grow a crop, feed it to an animal as it builds up muscle mass, then eat the animal.

Environmental Working Group GHG Lifecycle Assessment of foods

Greenhouse gas lifecycle assessment for common proteins and vegetables (EWG 2011).

How do the numbers get misrepresented?

There are often suggestions that going vegan is the most important step people can take to solve the global warming problem.  While reducing meat consumption (particularly beef and lamb) reduces greenhouse gas emissions, this claim is an exaggeration.

An oft-used comparison is that globally, animal agriculture is responsible for a larger proportion of human-caused greenhouse gas emissions (14-18%) than transportation (13.5%).  While this is true, transportation is just one of the many sources of human fossil fuel combustion.  Electricity and heat generation account for about 25% of global human greenhouse gas emissions alone.

Moreover, in developed countries where the 'veganism will solve the problem' argument is most frequently made, animal agriculture is responsible for an even smaller share of the global warming problem than fossil fuels.  For example, in the USA, fossil fuels are responsible for over 10 times more human-caused greenhouse gas emissions than animal agriculture.

That's not to minimize the significant global warming impact of animal agriculture (as well as its other adverse environmental impacts), especially from beef and lamb, but it's also important not to exaggerate its contribution or minimize the much larger contribution of fossil fuels.

Last updated on 27 November 2015 by dana1981. View Archives

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Comments

Comments 1 to 9:

  1. Very interesting. Thanks for putting things in perspective.

    However, it seems like this confirms part of the "Myth" you wished to debunk:

    "Becoming Vegan or cutting down on your own personal meat consumption could be the single most effective action that you can do to help reduce green house gas emissions."

    Short of going off the grid, that is. You have compared emissions from agriculture to emissions from the fossil fuel industry. Since your case seems to be built for the US where much power/electricty comes from fossil fuel, a person can hardly act so as to stop using fossil fuels. Even by selling their cars. However, they can stop eating meat.

    So it seems, although the impact of animal agriculture is sometimes overblown, eating a plant-based diet would still be the single most effective action an individual could undertake, short of going off the grid. No?

  2. "eating a plant-based diet would still be the single most effective action an individual could undertake, short of going off the grid."

    If you look at where the individual contributions of energy use are (eg the MacKay analysis for UK is here - I have done similar for NZ), you would see that food and even going off grid arent that big a deal (particularly if you use non-FF heating). Getting off the plane is probably the biggest saving you can make. Finding ways to get out of the car would be next followed by sharply reducing your consumption of stuff.

  3. Thanks for this great discussion.

    Check out this Eshel paper-Climate impact of beef: an analysis considering multiple time scales and production methods without use of global warming potentials- R T Pierrehumbert1 and G Eshel2

    Published 4 August 2015 • © 2015 IOP Publishing Ltd • Environmental Research Letters, Volume 10, Number 8

    http://m.iopscience.iop.org/article/10.1088/1748-9326/10/8/085002/meta

    The study conclusions include that certain forms of pastured beef have substantially lower climate impact than feedlot systems.

    To full address climate change impacts, we need to consider different types of livestock management — for their threats and potential benefits — ghg emissions reductions/sequestration as well as natural water storage, flood mitigation, and biodiversity enhancement...

    It seems we should eat much less beef and when we do eat it, we need to it the right kind...

    Also, my understanding is that all agriculture (not just livestock) GHG emissions are estimated at 15% of global total by FAO 2013; and 13% by UNEP 2015.

    Response:

    [PS] fixed link.

  4. I'm concerned with the presentation of this page http://www.skepticalscience.com/how-much-meat-contribute-to-gw.html.

    The Zero Carbon Australia Land Use Report found that a proper and full accounting of GHG emissions pegs Land Use at 55% of emissions using 20 year GWP. As you'd be aware 20 yr GWP is significant, given the perilous state of many climatic system and stocks of ice etc. Even using 100 year GWP which tends to obscure the effects in near term on climate systems of methane and black carbon it will soon be at 100 years,

    The major contributing factors were found to be land clearing (often cyclical), savannah burning (repeated) and centric fermentation. This would make it likely that GHG emissions in North and South America might be in that vicinity given the large amount of Amazonian and other old growth forest clearing going on to grow cattle and soy crops to feed north american cattle.

    90% of that 55% of national emissions using 20yr GWP is associated with livestock ruminants, mostly the large extended zone pastural operations in northern Australia, mostly for cattle.

    By presenting this argument using standard UNFCCC accounting which majorly obscures, re-assigns and ignores emissions and removal of sequestration sources associate with Land Use Sector you are in fact perpetuating a myth not debunking one.

    To my best knowledge the ZCA Land Use Report was peer reviewed and supervised within MSSI (University of Melbourne) and has not be refuted in the literature. Nor has it's conclusion that 55% of Australia's national GHG emissions using 20 yr PWG are from the Land Use Sector. I'd ask the you rename these pages to be less pejorative and more in line with the science and debate if you want to call it that.

    Given that much of the old growth forest clearing going on in the world to produce more ruminnent grazing pasture and crops to feed ruminents and  animals in general, and that this OGF is the greatest CO2 sequester known to man, and that it's impossible to regain the sequestration levels once OGFs are logged, even after a century, it's doubly important that land use sector emissions be seen as the major problem, perhaps the greatest problem in the short term for GHGs reduction (ignoring the politics of livestock lobby vs ff lobby), then renaming this Page and the old version is required. 

    Alastair Leith
    Climate Activist and Campaigner

     

  5. Zero Carbon Australia Land Use Report

  6. The Zero Carbon Australia Land Use Report (link fixed) mentioned above:

    "A number of agricultural industries are among the most emissions intensive activities in Australia. Beef production, for example, is more emissions intensive than aluminium and steel production. Emissions from agriculture are even more significant when the impact of activities is calculated over 20 years instead of the more common 100-year accounting approach. When considered from this perspective, agricultural emissions could account for as much as 54% of Australia’s total emissions."

  7. Yes, the 100 horizon for methane is whistling in the dark, presuming there are no non-linearities and tipping points in the near future.

  8. OK, I have a question... So, supposedly not eating meat will reduce carbon emissions and help reduce global warming correct ? But so far it seems the main way animal agriculture contributes to global warming is through deforestation for feedcrops and pasture land. If more humans start eating plants instead of animals however, while the need for pastures and feed crop land will reduce, won't the need for farmland to grow all these in demand plants just increase ? For example the U.S is already unable to produce enough fruits and veggies to feed its citizens and relies on other countries as a supplement..if the decrease in land needed for animals doesn't match up to the increase in land needed for plant farming , won't this result in even more land cleared in other places to keep up with supply and demand (aka money to be made ? )

  9. Theresab @8, this SKS page discusses the issue directly.  Essentially, deforrestation contributes more to global warming than does agriculture (18.2% vs 13.5%), but most deforrestation is driven by the lumber industry, not land clearing for agriculture.  From agriculture, the major contributors are agricultural soils (6%) and livestock and manure (5.1%).  All percentages are of global totals in CO2eq, from 2000 data.

    Crops require far less land area than does pasturing cattle.  Indeed, in general, you will require 10 times as much land area for animals as you will for plants for the same total food production.  That said, some area on which livestock is grazed is not suitable for cropping due to inadequate rainfall or other factors. 

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