Was looking into this because of that recent Paul McCartney article that was shared, and wanted to share what I found:

Here’s a good breakdown of differences between vegan & vegetarian diets in terms of climate impact: https://www.nature.com/articles/s43016-023-00795-w

Emissions:

  • Vegan:............. CO2: 2.16, CH4: 04.39, N2O: 0.71
  • Vegetarian:........ CO2: 3.33, CH4: 20.21, N2O: 0.98
  • medium meat-eaters: CO2: 5.34, CH4: 40.88, N20: 1.73
  • high meat-eaters:.. CO2: 7.28, CH4: 65.40, N2O: 2.62

So vegans have 30% of the emissions as high-meat-eaters, and the differences between vegans and vegetarians are significant with regards to their emissions, particularly methane emissions due to the significantly higher consumption of cheese by vegetarians.

(EDIT: it has been suggested it’s worth clarifying that vegan diet having 30% CO2 emissions means that there was a 70% reduction in CO2 emissions, and that methane emissions were reduced by 93% going from high-meat to vegan.)

Vegetarians ate significantly more cheese (30 g / day) than even meat-eaters (19 g / day), despite eating less dairy overall otherwise.

Also should be noted that there is a big gap between biodiversity impact between vegans and vegetarians, with vegetarian diets causing nearly double the number of species extinctions per day than vegan diets.

I was surprised that water use was so similar between vegans and vegetarians considering how much cheese vegetarians eat.

I still would recommend a vegetarian diet to meat eaters, as it’s still a massive improvement (and in my experience, it’s easier to become vegan once vegetarian), just thought it was interesting to actually quantify differences between veganism and vegetarianism in terms of climate impact.

  • Jim East@slrpnk.netMEnglish
    1·
    5 days ago

    they aren’t looking at what carbon opportunity costs exist if we sequester carbon in other ways, e.g. an equally implausible alteration as ending all animal agriculture and replacing the land used for animal agriculture with carbon sequestration would be to eliminate cars entirely and to replace parking lots with trees

    How would you even account for this? You couldn’t count it as part of the carbon opportunity cost of fossil fuels, as some cars are electric. You couldn’t count it as part of the carbon opportunity cost of industry, as the industry that makes the cars is not responsible for constructing the parking lots. You would need to look at every aspect of car culture from mining the materials to manufacturing the cars to constructing the roads and parking lots and determine how much deforestation is involved in every step of the process, which would be no easy feat, especially as the ratio of gasoline to electric cars is now changing relatively rapidly and the footprints of these different types of cars would differ as a result, and then calculate the carbon opportunity cost of cars on the whole as a separate category (which would make the totals add up to more than 100%, as there would be overlap with the footprints of fossil fuels and industry, for examples). If you wanted to calculate ONLY the carbon opportunity cost of the land area used for parking lots not being forested, then that would be a much easier calculation, but it isn’t really fair to criticise Sailesh / Climate Healers or the sources that they cite for not running those numbers; that is a very specific climate footprint to track compared to agriculture, industry, forestry, etc.

    • dandelion (she/her)@lemmy.blahaj.zoneOP
      1·
      5 days ago

      if you are going to estimate what percent of emissions are from animal agriculture vs transportation by looking only at “carbon opportunity cost” of animal agriculture and not doing anything to estimate the equivalent carbon opportunity cost of transportation, doesn’t that create obvious problems for the comparison?

      and yes, it is fair to criticize Sailesh for not considering carbon opportunity cost of other sources of greenhouse gases when making claims about animal agriculture being the number one contributor to climate change on that basis, that’s my point

      here’s an analogy: what if someone only looked at CO2 emissions from cars and animal agriculture, and ignored methane emissions entirely from animal ag? Wouldn’t you feel that the claim that cars create more emissions on that basis alone leaves out important information? Since methane is a significant greenhouse gas, and large amounts of it are produced by animal ag, to be intellectually honest you would want to measure and compare all significant greenhouse gases from both cars and animal ag to make a real comparison.

      My point was just that: you can’t calculate carbon opportunity cost of animal ag and not do anything to calculate something equivalent for other sources of greenhouse gases (like transportation) if you are being intellectually honest and are actually trying to make a comparison.

      Considering Sailesh’s past associations with intellectual dishonesty, however, it isn’t surprising to see that here as well.

      • Jim East@slrpnk.netMEnglish
        1·
        3 days ago

        Here you can see the numbers without the COC included (X% + COC), so that is a more “apples to apples” comparison…

        I haven’t actually done the measurements and repeated all of the calculations, so I can’t verify these or any other numbers, but from what I observe in the world, “common sense” suggests that animal agriculture does in fact have the largest ecological impact. When we consider the aerosol emissions from coal and oil, the ERF (not necessarily GHG emissions) of animal agriculture being greater than that of fossil fuels doesn’t seem like much of a stretch. Ultimately it doesn’t matter so much if the numbers are off; both the exploitation of non-human animals and the burning of fossil fuels will need to end, and the former is much easier to end quickly with minimal disruption to infrastructure.