How much do lambs really contribute to global warming?

A recent report from WWF argues that lamb stew contributes more to global warming than fish and chips or two other iconic British dishes.  In many ways, sheep and cattle grazing, properly managed, seems more sustainable than dependence on ocean fish, given overfishing and the increasing temperature and acidity of the ocean caused by our excessive releases of CO2.  Grazing is the original no-till (erosion-preventing) system.  Where erosion isn’t a concern, rotating between perennial pastures and annual crops is a great, low-input way to control weeds, few of which can survive both grazing and tillage. Also, mixed grass-legume pastures can get most of their nitrogen from biological nitrogen fixation (the main focus of research in my lab) rather than fertilizer.  These are some of the reasons why organic farmer, Jim Bender, considers grazing animals key to pesticide-free farming.

The WWF estimate of lamb’s high greenhouse-warming contribution is based on their burping and farting methane.  Methane absorbs 30 times as much infrared radiation as an equivalent amount of CO2, making it a powerful greenhouse gas.  But, sooner or later,  methane gets oxidized to CO2 so its long-term greenhouse-gas contribution is less than the 30X-greater-than-CO2 that is widely assumed.  How much less depends on how long it takes for the average methane molecule to get oxidized to CO2.   Perhaps one of my dozens of readers can answer this question.

Another thing that bothered me about the WWF report is the claim that the UK needs to reduce its daily per-capita CO2-equivalent production by about 1 kg (from 5.17 kg  to 4.09 kg — wow, three significant digits!) by 2030, out of a daily total of 35.6 kg.  Like most economists, I think a sufficiently-large carbon tax would be the most-effective way to reduce greenhouse-gas emissions, while letting individuals decide whether they’d rather add insulation or solar panels to their homes, drive less, or eat differently.  Taxing oil, coal, and natural gas wouldn’t directly penalize methane production by sheep and cattle, so maybe we’d need a separate tax on systems that produce methane.  But that tax should be based on how long methane stays in the atmosphere before being oxidized to CO2, rather than on the assumption that it keeps its 30-fold greenhouse effect forever.

5 thoughts on “How much do lambs really contribute to global warming?

  1. Dear Professor. I agree with your view. But, it is interesant to highlights that the most current consensus in ecology of the agrifood system indicates that agrifood system is the major driver of the Earth system exceeding planetary boundaries for any kind of life. Clearly, sustainability of this kind of system depends depends of many components, that in my best knowledge, is more like defined as a wicked problem. Because, although, a generalized axiom in soun science, it is urgent to reduce the global consumption of processed meat and its derivatives. The healthy diet of an agnostic culture, considers proteins and fats of animal source, in its just measure, without excesses and high ethical standards during the productive process. It is like a socio-ecological dilema to social change; How to consume less meat for a sustainable agrifood system? I think that is a mix of many ways of thinking the social change. As instance, “econoutopians” really thinks that taxes are the best drivers. For “technoutopians” really thinks that technological determinism is the best, or “normativeutopians” really thinks that only policy works, and “antropoutopians” really thinks that culture is a continuous learnng process.

    Have a nice day, regards!

    Víctor

    PD: Some of these ideas, I read them in:

    Guillen-Royo, M. (2016). Sustainability and wellbeing: human scale development in practice. Abingdon, Oxon ; New York, NY: Routledge, Taylor & Francis Group.

    Hidalgo, C (2015). Why information grows? The evolution of order, from atoms to economies. Basic Books

    Swinburn, et al., (2019). The Global Syndemic of Obesity, Undernutrition, and Climate Change: The Lancet Commission report. The Lancet, 393(10173), 791–846. https://doi.org/10.1016/S0140-6736(18)32822-8

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    1. Victor,
      Thanks for your comment. An important point is that a million people eating less meat, using less energy, and (most important) having fewer children wouldn’t have much effect, with a global population over 7 billion. We need to change the behavior of the most-prodigal billion, at least. And if a billion people stopped eating meat, the immediate effect would be a decrease in meat prices which would let the next billion or two start eating more meat. Given cultural divisions within and among countries, I don’t see much hope for enough global cultural change to solve this problem. I guess I’m an econotopian, thinking that a global carbon tax that would slow global warming with fewer negative side effects than policies developed by ignorant and corrupt politicians. Without global cooperation, though, the greatest impact may come from inventions (no-till farming, teleconferencing software, etc.) that make more-sustainable practices more profitable or convenient than less-sustainable ones.

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  2. Technical solutions can help of course, and it might push their adaptation along faster if there were market signals such as higher taxes to persuade both investment and adoption.

    Back in January I posted a piece reviewing how clover can be bred to reduce methane emissions from consuming ruminants. It’s here:

    https://gulliverspulse.wordpress.com/2019/01/04/clem-claims-climate-clever-clovers-courageous-not-clueless/

    There also appears to be some variation within the ruminant “germplasm” for lower methane output (leads to that literature are mentioned in the linked piece). And one might also look to modifying the gut microbiome… though I have no reference to point to on that front.

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