By the way, the paper “The animal welfare cost of meat: evidence from a survey of hypothetical scenarios among Belgian consumers”, which seems relevant to this post, was evaluated by The Unjournal – see https://unjournal.pubpub.org. Please let us know if you found our evaluation useful and how we can do better; we're working to measure and boost our impact. You can email us at [email protected], and we can schedule a chat. (Semi-automated comment)
Thanks for the post. This makes sense - so many more deaths are caused by eating more chicken that it makes sense to avoid it altogether. This reminds me of the recommendations done in One Step for Animals.
However, I am a bit bothered that the climate change study doesn't include the impact on famines, wars, infectious diseases, floods and other risks - since they are by far the biggest risks. The biggest danger of climate change isn't heat - it's that it changes absolutely everything else in the Earth system.
I have a found another study that thinks there is 1 additional deaths for 1000 tons emitted : https://www.frontiersin.org/articles/10.3389/fpsyg.2019.02323/full#h5. What do you think about it ?
This doesn't change your conclusion that meat should be avoided altogether I think.
According to this study, the excess deaths from temperature are much larger than the deaths from climate change related famines, floods,... I'm not sure if deaths from wars have to be included, because I would say the aggressor who starts the war is responsible for those deaths.
I don't have access to the study (I may find a way to access it later). I'm just surprised by the result.
The most pessimistic pathway without mitigation would result in a net economic impact equivalent to 6.6% (3.9–8.6%) of global GDP at the end of this century.
This impact sounds awfully small. The worst climate causing a decrease of 4% to 8% GDP?
Are these impacts derived from DICE or calculations by Nordhaus, or his peers ? If yes, there are huge methodological flaws in the way this results was obtained (for instance, they only model the impact on GDP for outdoors activites).
I recommend watching this video to understand commons limits of calculations made on GDP impacts.
This papers on the topic is also very interesting.
I really deaths from war should be included, if the war wouldn't have taken place without climate change (which is of course very hard to evaluate - climate change is one factor that adds pressure but is combined with others).
Neither DICE nor calculations by Nordhaus were used in that study. Here I was not talking about the impact on GDP, but on the expected deaths from undernourishment, fluvial flooding,... (supplementary material figure 3) (These deaths were then used to calculate loss of economic welfare in monetary terms using the value of a statistical life, but that contestable step is not important here.)
Ok, I don't really have the time to look into this in detail, this just sounds very much like an underestimate (especially as economic predictions usually don't include tipping points, cascading risks, and include poorly tail risks).
For instance, at -5°C compared to preindustrial during the last ice age, the North of America and Europe (including Canada and Scotland) were under a 3km thick ice sheet. I fear current climate change damage models would count this as a 4% GDP loss.
Thanks for referring to that study. That 1 death per 1000 tons is in the same order of magnitude of the 1 death per 4000 tons that I used based on Daniel Bressler's study. So I think the main takeaways are still valid. But yes, there is a possibility that deaths from climate induced famines, wars,... are some orders of magnitude larger than deaths from temperature change
Just read the article by Parncutt about the 1000 tonne rule. Apparently, it is 1 death per 1000 tonnes of carbon, i.e. 1 death per 3700 tonnes of CO2, close to Bressler's estimate
I'd like to see if this analysis holds up if you change the human deaths this century per kgs variable (as well as took into account wild animal deaths).
The "0,00000025" just comes from Bressler 2021, from what I see. I did some calculations to see how much the Bressler rate differs from another rate I've read about--the Climate Vulnerability Monitor. It's possible the Bessler number undercounts by a factor between 1:2 and 1:34
Key limitations with my numbers:
I am sorry but this article is naive at best and misleading at worst. Crickets lifecycle is extremely short, they can live a full life cycle before processing, unlike humans starving to death and butchered livestock. These deaths can not and should not be compared by any metrics. It is very comfortable to judge solutions to world hunger from the ebony tower, where it is thought wise to shred a tear over crickets than humans in need of nurturing.
Also the more I think about it, linking the value of life to neurons is a slippery slope.
Despite all of that, most of the policy suggestions are great.
Post summary (feel free to suggest edits!):
A recent study (Bressler, 2021) estimated that for every 4000 ton CO2 emitted today, there will be one extra premature human death before 2100. The post author converts this into human deaths per kilogram of meat produced (based on CO2 emissions for that species), and pairs this with the number of animals of that species that need to be slaughtered to produce 1kg of meat.
After weighting by neurons per animal, their key findings are below:
This suggests switching from beef to chicken or insect meat reduces climate change but increases animal suffering significantly, so might be bad overall. They suggest prioritizing a reduction of chicken meat consumption, and that policy makers stop subsidizing research on insect meat, tax meat based on climate and suffering externalities, and start subsidizing plant / cell based meat.
(If you'd like to see more summaries of top EA and LW forum posts, check out the Weekly Summaries series.)
Hi Stijn,
Interesting post!
I have a few questions about your meat-to-animal conversions.
1. In the "Deathprint of meat" section you clearly cite the sources for the meat-to-emissions conversions, but not the meat-to-animal conversions. From reading further down the piece it seems they probably come from Saja, K. (2013). Is that correct?
2. Saja (2013) seems to calculate 2 kg of chicken meat for "Average animal products per one animal life", which would be 0.5 chickens per 1kg though in your table you have 0.667 for animals killed per kg meat for chicken meat. I think that 0.667 is Saja's figure for Fish (1.5kg of meat per 1 fish)?
3. If you did use Saja (2013), I wonder if you could elaborate on why, especially since as you note it "excludes the animals used as feed (e.g. fish meal and insect meal given to farm animals)." One could also use the conversion factors from Faunalytics (2020) which I believe do include feed fish (here 1kg of chicken meat would be associated with 0.87 animal deaths). There are of course also other more recent conversions Warren (2018), Hurford (2014) for number of animal deaths, and for days of life (or suffering) e.g. Drescher (2017), Tomasik (2007).
Hi Neil,
my meat-to-animal conversions were not based on Saja, but simply on the weight of edible meat produced by an animal. For chickens, I used the slightly more conservative value of 1.5 kg edible meat per broiler chicken, instead of Saja's 2 kg. That means 1/1.5=0.66 animals/kg. Perhaps broiler chickens in the US grow heavier and are closer to Saja's 2 kg per chicken?
Haven't thought about using those other sources like Faunalitics. Thanks for mentioning it.
Animal-based meat production is a large contributor to climate change. Especially beef has a high a carbon footprint, measured in terms of kilogram CO2-equivalents per kilogram of meat. Switching from beef to chicken meat or insect meat lowers greenhouse gas emissions and hence decreases future climate change damages. But chicken meat has a much higher moral footprint (Saja, 2013) or welfare footprint (welfarefootprint.org) than beef. Chickens experience more intense suffering and more hours of suffering for one kilogram of meat, compared to beef cows.
This article shows that the increase in moral footprint when switching from beef to chicken meat or insect meat is likely to be worse than the decrease in carbon footprint. To compare these footprint changes, all the footprints are expressed in terms of the deathprint: the number of humans dying prematurely from climate change and the number of animals killed (slaughtered) in animal farming, for the production of one unit of meat.
A recent study (Bressler, 2021) estimated the net number of humans dying prematurely from temperature changes (especially heat waves) due to climate change, before the year 2100. An extra emission of 4000 ton CO2, emitted today, results in one extra human death due to climate change, in the business as usual scenario where everyone else does not take measures to reduce their emissions. Hence, 0,00000025 humans will be killed this century by emitting one extra kilogram of CO2.
I use this number of deaths for the calculations below, although this number is both an underestimation and overestimation of the total human deaths due to climate change. It is an underestimation, because it does not include deaths from e.g. famines, wars, infectious diseases, floods and other risks that are increased by climate change. On the other hand, this number is an overestimation in the sense that climate change adaptation measures and CO2 emission reduction measures are likely to be taken. If poor countries develop and become richer, people in those countries can take more adaptive measures such as installing air conditioning, which lowers the mortality rate from extreme temperatures. And if global CO2 emissions are reduced, the impact of an extra unit of CO2 emissions (i.e. the marginal mortality rate) reduces as well (due to the non-linear relationship between amount of CO2 in the atmosphere and climate damages).[i]
The table below shows the amount of meat produced by one animal, and the carbon footprints of meat products. These footprints measure the greenhouse gas emissions, in terms of CO2-equivalents, including all life cycle emissions as well as land use change emissions from e.g. deforestation, for the production of one kilogram of meat. The values of beef, pork and chicken are taken from Pieper e.a. (2020), which applies to Germany. The carbon footprint of insect meat is assumed to be lower than the footprint of chicken meat but slightly higher than the footprint of plant-based protein. The chosen value is a preliminary estimate of cricket meat, taken from Blonk e.a. (2008). It requires roughly 10.000 crickets for the production of one kilogram of cricket protein powder.
| kg meat per animal consumed | animals killed per kg meat | kg CO2 per kg meat | |
| beef | 300 | 0,003 | 37 |
| pork | 100 | 0,010 | 10 |
| chicken meat | 1,5 | 0,667 | 16 |
| insect meat | 0,0001 | 10.000 | 2 |
With these values, we can calculate the human and animal deathprints of meat, i.e. how many humans will die from climate change and how many animals are killed (slaughtered) for the production of one kilogram of meat. This animal deathprint of meat only includes the animals that will be consumed by humans, and excludes the animals used as feed (e.g. fish meal and insect meal given to farm animals). This means the displayed deathprint of meat is an underestimation of the total number of animals that are used for food.
| human deaths from climate change per kg meat | animals killed per kg meat | animals killed per human death | |
| beef | 0,0000093 | 0,003 | 360 |
| pork | 0,0000025 | 0,010 | 4.000 |
| chicken meat | 0,0000040 | 0,667 | 166.667 |
| insect meat | 0,0000005 | 10.000 | 20.000.000.000 |
Producing 108 tons of beef will cause one human death from climate change and an additional 360 cows killed. Producing 250 tons of chicken meat will cause one human death from climate change and almost 170.000 chickens killed.
Perhaps the value of a chicken life is less than a human life. How much chicken deaths is equivalent to one human death? The level of consciousness or intensity of experiences of chickens might be lower than the level of consciousness of (adult) humans, and this could mean a chicken is worth less than a human. It could be (but is far from obvious) that the level of consciousness correlates with the number of neurons in the brain. As a sensitivity analysis, I calculate a weighted deathprint, with neuron count as weights.
The table below shows the number of neurons for different animals (taken from Carl Shulman’s article). A human as 85 billion neurons. Hence, one human death corresponds with 85 billion human neuron deaths. One insect death corresponds with 200.000 neuron deaths.
| number of neurons in the brain | brain mass (gram) | |
| human | 85.000.000.000 | 1350 |
| cow | 3.000.000.000 | 440 |
| pig | 1.200.000.000 | 180 |
| chicken | 220.000.000 | 4 |
| insect | 200.000 | 0,002 |
The next table shows the neuron weighted deaths (or neuron deaths) for different meat products. Even when weighting the value of a life by neuron count, one human death corresponds with 47.000 insect deaths.
| neuron weighted human deaths from climate change per kg meat | neuron weighted animals killed per kg meat | neuron weighted animals killed per neuron weighted human death | |
| beef | 786.250 | 10.000.000 | 13 |
| pork | 212.500 | 12.000.000 | 56 |
| chicken meat | 340.000 | 146.666.667 | 431 |
| insect meat | 42.500 | 2.000.000.000 | 47.059 |
What if a consumer switched from beef to chicken meat, or from chicken meat to insect meat? The next table shows how many humans are saved (by reducing climate change) and how many extra animals are killed when replacing one meat product with another.
| replacement | humans saved per kg meat replaced | extra animals killed per kg meat replaced | animals killed per human saved | animals killed per cow saved | animals killed per chicken saved |
| beef by chicken meat | 0,000005 | 0,663 | 126.349 | 200 | 0 |
| beef by insect meat | 0,000009 | 10.000 | 1.142.856.762 | 3.000.000 | 0 |
| chicken meat by insect meat | 0,000004 | 9.999 | 2.856.952.381 | 0 | 15.000 |
If a consumer eats one kilogram of chicken meat instead of one kilogram of beef, five millionth of a human is saved from a premature death caused by climate change.[ii] But almost one extra animal is raised on a farm and killed (slaughtered). This means that switching from beef to chicken meat results in (net) more than 100.000 animals killed per human saved.
Note that the life of a present-day farm animal being slaughtered is most likely worse than the life of a future human who is prematurely killed by a heat wave due to climate change. Most people believe that most farm animals, especially chickens, have lives not worth living, with more negative than positive experiences, dominated by suffering over pleasure (Espinoza & Treich, 2021; Bruers, 2022). In contrast, climate change is unlikely to become so terrible that it causes future humans to have lives not worth living. This means the ‘100.000 animals to 1 human’ ratio is an underestimation of the overall disvalue (badness) of a present-day chicken suffering on a farm and being killed in a slaughterhouse relative to a future human dying from climate change. In this article, I neglect the disvalue of suffering during one’s life and focus only on the disvalue of death.
If you value a chicken life as less than one in 100.000 of a human life, in the sense that a human death is more than 100.000 times worse than a chicken death, you may believe that switching from beef to chicken meat is good overall, that the benefits for humans trump the costs for animals. Switching from beef to insect meat would be good overall if you value an insect life as less than one in a billion of a human life. If you value the life of a chicken as less than one in 200 of a cow’s life, switching from beef to chicken meat is net beneficial for the animals. If you value the life of an insect as less than one in 15.000 of a chicken life, switching from chicken meat to insect meat is net beneficial for the animals.
Is the life of a chicken worth less than 1 in 100.000 of a human life and less than 1 in 200 of a cow’s life? Let us see what happens if we weight the lives of humans and animals by the number of neurons.
| replacement | neuron weighted humans saved per kg meat replaced | neuron weighted animals killed per kg meat replaced | neuron weighted animals killed per neuron weighted human saved | neuron weighted animals killed per neuron weighted cow saved | neuron weighted animals killed per neuron weighted chicken saved |
| beef by chicken meat | 446.250 | 136.666.667 | 306 | 15 | 0 |
| beef by insect meat | 743.750 | 1.990.000.000 | 2.676 | 200 | 0 |
| chicken meat by insect meat | 297.500 | 1.853.333.333 | 6.230 | 0 | 109 |
I think it is unreasonable to value the life of a human more than 300 times the life of a chicken after weighting by neuron number. Such a valuation of a human life over a chicken life might correspond with for example a belief that the probability of a chicken being sentient (having a consciousness) is less than one in 300, which is unreasonably low. That means it is unreasonable to value a human life (not weighted by neuron count) as more than 100.000 higher than a chicken life.
Similarly, I think it is unreasonable to value a cow’s life more than 15 times a chicken life after weighting by neuron count (and hence 200 times higher without the neuron count weighting). Therefore, I think switching from beef to chicken meat is bad overall: the twofold reduction in the human deathprint from climate change (i.e. a decrease in carbon footprint with roughly 50%) is offset by a two hundredfold increase in the animal deathprint (i.e. a factor two hundred increase in the moral footprint).
The case against insect meat also becomes clear: switching from chicken meat to insect meat corresponds with more than 100 insect neurons killed per chicken neuron saved. Is a neuron weighted chicken life worth more than 100 neuron weighted insect lives? Perhaps you believe the probability of a chicken being sentient is more than hundred times higher than the probability of an insect being sentient? That would mean the probability of an insect being sentient is lower than one percent. But this seems unreasonable, in light of all currently available evidence of insect sentience (see for example the Welfare Range Table from the Moral Weight Project).
Switching from beef to chicken meat reduces climate change but increases animal suffering. The increase in animal suffering when eating chicken instead of beef is most likely worse than the increase in climate change when eating beef instead of chicken, making the switch from beef to chicken bad overall. Similarly, the switch from beef or chicken meat to insect meat might be bad overall, because much more animals (insects) are killed for an amount of insect meat compared to an amount of beef or chicken meat.
Blonk, H., Kool, A., Luske, B. (2008). Milieueffecten van Nederlandse consumptie van eiwitrijke producten (in Dutch, Environmental effects of Dutch consumption of protein-rich products). BMA/VROM, Gouda.
Bressler, R. D. (2021). The mortality cost of carbon. Nature communications, 12(1), 1-12.
Bruers, S. (2022). The animal welfare cost of meat: evidence from a survey of hypothetical scenarios among Belgian consumers. Journal of Environmental Economics and Policy, 1-18.
Espinosa, R., & Treich, N. (2021). Animal welfare: Antispeciesism, veganism and a “life worth living”. Social Choice and Welfare, 56(3), 531-548.
Pieper, M., Michalke, A., & Gaugler, T. (2020). Calculation of external climate costs for food highlights inadequate pricing of animal products. Nature communications, 11(1), 1-13.
Saja, K. (2013). The moral footprint of animal products. Agriculture and Human Values, 30(2), 193-202.
[i] Furthermore, from a population ethical point of view, it is difficult to include the number of humans dying from climate change after the year 2100, because these humans are not yet born, and their existence depends on whether or not we take emission reduction measures. In the world where we take emission reduction measures, other people will be born compared to the world where we do not take those measures. If we emit an extra amount of CO2, there will be an extra increase in climate change, and a person in the far future could die from this extra climate change. But if we did not emit that extra CO2 and hence we did not cause that climate change, that person will not exist (other people may be born instead). It is not obvious to say that we saved a person when preventing the killing of that person would mean preventing the very existence of that person. I prevented the killings and premature deaths of all my unborn children who will never exist, but that does not mean I saved all those non-existing children.
[ii] I’m excluding market shift effects due to price changes. I assume the switch of 1 kg of beef to 1 kg of chicken meat corresponds with a decrease in total beef production by 1 kg and an increase in total chicken meat production by 1 kg.
While I'm sympathetic to your conclusion, it feels like a major omission to not think about added wild animal deaths due to climate change, in addition to the added human deaths. Did you look at all at the state of research on how climate change will impact wild animal populations? (Note: you might get into some morally tricky questions there. Climate change is going to hurt lots of existing species, but other species may replace species that are hurt by habitat loss and temperature changes. How exactly to morally weight that is probably more complex than just tallying up deaths).
Not much is known about the impact of climate change on wild animals, so therefore I excluded it. It is very complicated. First, it could still be the case that at the expected level of warming, the decrease in cold deaths of wild animals could be larger than the increase in heat deaths. Less freezing days, but more heat waves and forest fires... Second, it might be the case that most wild animals have a net negative welfare and that climate change decreases population sizes, which means fewer animals with net negative welfare will be born, and that is good in the long run. Third, animals have a shorter lifespan and higher reproduction levels than humans, which means the identities of future born animals may be much more dependent on what we (CO2 emitting beings) do, compared to the influence of our actions on the identities of future born humans. Compare the world where we take climate measures with a business as usual world. Already after a few years you will see that those two worlds will contain different animals. That brings us to the difficult non-identity problem in population ethics. So... it becomes very complicated.
I agree it's very complicated, but it seems possible the results from wild animal suffering/death could be enough to negate the gains you think will come from farmed animals. Hence, I think the policy recommendations should with a big uncertainty cauvea t. It's possible those recommendations could make things worse.
Hi Stijn,
Interesting analysis!
You say that:
However, if the effects on wild animals are the driver for the nearterm effects (as suggested in the table here), being clueless about them (for reasons such as the ones you provided) implies being clueless about the nearterm effects of replacing beef by chicken (or any other substitution). "Overall effect" = "certain effects" + "uncertain effects" can be approximated as:
Mathematically, you can conclude that E("overall effect") > 0 if E("certain effects") > 0 and E("uncertain effects") = 0. However, the sign of E("uncertain effects") is quite uncertain, so that conclusion would not be resilient. Under these conditions, further research makes more sense to me than advocating for specific subsitutions.
It might be possible to replace chicken partially with beef and partially with plants so that the environmental (and wild animal) effects have roughly 0 expected value, but the effects on farmed animals are positive. Maybe not, though, depending on how deep your uncertainty and how many different effects you need to balance.
I discuss this kind of approach more generally here: https://forum.effectivealtruism.org/posts/Mig4y9Duu6pzuw3H4/hedging-against-deep-and-moral-uncertainty
yes, good point
NPP is increasing, meaning There is more food available, and warmer climates means faster metabolisms and shorter lifespans for ectotherms, we should expect Climate change to increase the number of future animals.