Why the expected numbers of farmed animals in the far future might be huge


  • This post is essentially a case that factory farming could be a longtermist cause area. (but not a case that the current portfolio of work on factory farming are good or relevant for the future)

  • Alternatively, you can see this post as a response to claims similar to this: “The scale of the problem of factory farming itself (ignoring potential long-run benefits of animal advocacy) is small compared to the scale of issues affecting future generations.

  • Unlike previous attempts like this or this, this post does not base the case on arguments about the flow-through/​knock-on effects of farmed animal advocacy (or other animal advocacy).

  • I used the expected number of humans by (Future of Humanity Institute 2021), as a basis of my guesstimates. This formed my view that the case for concerning about farmed animals in the far future is at least as strong as the case for concerning about humans in the far future.

  • The strongest argument against the importance of this post is that, in expectation, artificial sentience will far outnumber the number of farmed animals. The caveat is that this argument would also suggest that humans are not of significant concern in the longtermist worldview.

  • The only intervention I am proposing in light of this proposed longtermist cause area, is to do research to update the guesstimates I provided in this post.

  • P.S. (2022 Jan 14). Thanks to Rohin Shah pointing out that the numbers in this post depend heavily on the probability (or your credence) that the universe will be filled mainly with digital people (In his words. I prefer to say “digital beings” when I discuss this topic). This is because digital people will, presumably, have very few incentive to raise animals for food, or even other purposes.

  • P.P.S. Thinking about the last point. I can actually think of one reason why digital beings might raise some animals. If bringing about animals somehow is the best way to extract resources from some planets (like, eat and then decompose stuff), they digital people might still do it.

Why this post?

In 10+ (I believe 12-14, I regret not tracking them seriously from the start) discussions (mine vs others, and also discussions I see on EA forum, podcasts, forwarded emails, etc.) about longtermism, I often heard from other longtermists claim that factory farming is a “shortermist”/​non-lontermist cause area. For example, 80000 hours said in their factory farming cause area profile: “The scale of the problem of factory farming itself (ignoring potential long-run benefits of animal advocacy) is small compared to the scale of issues affecting future generations.” The most often heard (in fact, I don’t remember a single case when it wasn’t) justification for this view is that, they believe, factory farming is grossly energy inefficient in comparison with its potential substitutes, especially cultivated meat, and therefore will likely (some say certainly) be replaced. I (and a few people in animal welfare and alternative protein spaces I talked to) am personally baffled by the level of certainty they tend to have on the claim, and also the lack of support further than the energy efficiency argument. Since then, I have found more and more evidence that this view is probably misinformed. And since the truth of this claim might have very significant implications for the longtermist picture (especially for people who focus more on S-risk then X-risk). I decided to write a post on it.

Applying the expected value theory, also to animal issues

Before going into the technical details of the topic. I want to discuss a bit about applying the expected value theory consistently. In quite a lot of discussions on the relation between animal welfare and longtermism, people made arguments like “I think a key objection for me is to the idea that wild animals will be included in space settlement in any significant numbers.“ Or “I’m pretty optimistic this won’t happen however. I think by default we should expect that the future (if we don’t die out), will be predominantly composed of humans and our (digital) descendants, rather than things that look like wild animals today.” I think this type of responses suffer from the same problem, that they are not strong enough to refute the case to regard some animal welfare issues as longtermist cause areas, because even if they are right to claim that future scenarios with a lot of animals are “unlikely”, the stakes might still be very high due to expected value calculations. As a comparison, 80000 hours made a similar argument for the importance of the long-term future even if one thinks humanity is “unlikely” to survive for long: “if you think there’s a 5% chance that civilisation survives 10 million generations till the end of the Earth, then (in expectation) there will be over 500,000 future generations.

There is also another type of response which doesn’t suffer from the same problem because they feel “certain” about claims that reject animals being a concern for longtermism. This example is a very typical one: “By that stage of technological development we will surely be eating meat produced without a whole animal, if we eat meat at all.” In my opinion, these claims of asserted certainty are not justified, and if they are wrong, the stakes can be extremely high, for similar reasons as the above. This post will explain why the claim that we will not have factory farming in the long-term future is not justified.

Quoting 80000 hours, “if you’re uncertain whether the future will be big, then a top priority should be to figure out whether it will be — it would be the most important moral discovery you could make.” This is what I am trying to do with this post, in the context of factory farming.

The argument of overwhelming expected numbers of artificial sentience

The strongest argument against the importance of this post is that, in expectation, artificial sentience will far outnumber the number of farmed animals I personally find this argument compelling, but feel extremely unsure how we should deal with uncertainties like, i. whether there will be artificial sentience, or ii. whether they will have the capacity to suffer, etc. Also, a big caveat I have is that this argument would also suggest that humans are not of significant concern in the longtermist worldview. I believe this is a position a lot of longtermists might not want to take. I personally think it would be unproductive to advocate for less concern for humans in the long-term. But to reduce my cognitive dissonance, my choice is to have more concern for animals in the long-term future.

How much is at stake (in expectation)

To come up with guesstimates about the far future, we probably need to start with current numbers. To stay as conservative as I can (and therefore as unlikely to refute what I want to refute as I can). For all the source data that has a range (lower to higher estimates) in the number of animals, I automatically take the lowest.

Step 1: In recent years (2016 to now, different data sets used different reference years), there were 80B terrestrial vertebrate (my own calculations using a series of data from FAOSTAT), 92B farmed finfish (Open Philanthropy, 2019), 260B (260B − 530B) farmed shrimps (Rethink Priorities, 2020 unpublished), and 1000B (1000B − 1200B) farmed insects (Rethink Priorities, 2020) slaughtered each year. If we divide them into vertebrates and invertebrates, we get 172B and 1260B respectively. (Note: I ignored numbers of animals that are not farmed for meat, but their products, such as milk, eggs, fur, and leather, because their statistics are more messy, and adding them won’t change the total numbers by significant portions.)

Step 2: Then I propose to turn this into a ratio of farmed animals per human life. Since the data for the farmed animals were roughly taken at 2017, on average, I will take the 2017 human population figure, which was roughly 7.6B (UN 2017). Therefore, we can conclude that in 2017, humans slaughtered 22.6 vertebrates and 165.8 invertebrates per (human) capita.

Step 3: Finally, I propose to turn these numbers into the number of farmed animals slaughtered per human in our whole lives. According to the World Bank, the average life expectancy from birth in the world was 72.391 in 2017. This means that each current generation human caused 1636 (1600 hereafter) vertebrates and 12002 (12000 hereafter) invertebrates to be slaughtered in our lifetime. I called these numbers per human capita of farmed animals (PHCFA). We can then use these numbers to extrapolate how many farmed animals there will be in the future.

I propose to use the expected number of humans by (Future of Humanity Institute 2021),as a basis of my guesstimates. Extrapolating from their estimates for number of humans in the future, I came up with my guesstimates of number of farmed animals in the future, and this formed my view that the case for concerning about farmed animals in the far future is at least as strong as the case for concerning about humans in the far future. It is important to clarify that I didn’t form the view that farmed animals are in expectation the largest group of moral patients in the future, just that their expected numbers are high enough to be of concern under a longtermist perspective

(Future of Humanity Institute 2021) estimates that, in expected value terms, there will be 1.1 * 1014 expected human lives in the future. But the report also estimated, also in expected value terms, considering the chances of successful space settlement and other factors, the number of humans in the future outside of earth. The table below summarizes the estimates:

Expected human lives in the future
Earth only1.1 * 1014
Solar system only5 * 1025
Milky way only2.5 * 1034
Affectable universe5 * 1045

Table 1: Estimates of expected lifespan and population size of humanity

We can now therefore estimate the number of farmed animals in the future if PHCFA stays at the 2017 level. For example, if you believe that we will never leave the earth, the conservative estimate would be 1.1 * 1014 * 1600 = 1.76 * 1017 for vertebrates, or 1.32 * 1018 for invertebrates. But clearly, we cannot simply assume that factory farming will stay at the 2017 level. I will therefore try to come up with the guesstimates of PHCFA (future), from PHCFA (2017).

Below was my mental process for coming up with the calculation, you can read step 1 and skip the rest and go directly to the table. If you are interested, or if the table didn’t make sense to you, my mental process was roughly like this:

Step 1: PHCFA (future) /​ PHCFA (2017) = coefficient (R)

Step 2: To simplify my calculation and presentation, I assumed that there is no probability distribution for different values of R, and that I have only one prediction for each scenario (e.g. invertebrate farming on earth only). I choose the value of R that is the most likely to me, and only assign a probability to that outcome. For example, invertebrate farming on earth only. I just assumed that there is only one outcome possible: R = 1 (the outcome that is the most likely in this scenario to me), and the probability of this happening is 30%.

Step 3: R (most likely) * Probability for R (most likely) = Expected value of R

Step 4: Expected number of farmed animals in the future = Expected value of R * expected human lives in the future

With that, my views are summarized in the following table:


R (most likely)

Probability for R (most likely)Expected value of R
Earth onlyVertebrates




Solar system onlyVertebrates




Milky way onlyVertebrates




Affectable universeVertebrates





Table 2: My beliefs on R in different scenarios, and the resulting products (expected values of R)

Farmed animals slaughtered per human 2017Expected ratio of factory farming compared to 2017

Expected human lives in the future

Expected number of animals farmed and slaughtered in the future
Earth only




1.1 * 1014

1.0 * 1016



50% 6.6 * 1017
Solar system only




5 * 10258 * 1027




6 * 1028
Milky way only




2.5 * 10342 * 1035



2.5% 7.5 * 1036
Affectable universe



0.05% 5 * 10454 * 1045



0.5% 3 * 1047

Table 3: Expected number of animals farmed and slaughtered in the future

Why we shouldn’t expect factory farming to be 100% eliminated

Now we get to the claim that needs the most justification. These considerations, together, formed my views summarized in the tables above.

I. Not all types of factory farming are equal

When the term factory farming is mentioned, the picture people have in mind or get when they google it are usually chickens, pigs, and cows. This is quite expectable as these are the animals that the Western farmed animal movement had focused on in the one to two decades or so. But this kind of picture might provide a few wrong impressions. First, these animals actually do not represent the majority of farmed animals even if we are counting just vertebrates, as the total number of fish is more than double than of the total number of these three animals combined (OPP 2019 compared with Statista 2022). The total number of animals farmed would be more overwhelmingly larger than these three animals if invertebrates are also included. Second, the biggest problems from the raising of these three animals might be lower for the raising of some fishes and invertebrate species. For example, the raising of cows is known to be one of the highest (with lambs and goats) in carbon and water footprint, and while the raising of chickens and pigs are less bad in this regard than the raising of cows, they are still higher than the raising of fishes and invertebrates. The raising of these three animals also produce more manure per weight of animal farmed than the majority of the raising of fish and invertebrates. Also, the raising of cows, chickens, and pigs all are believed to have epidemic or even pandemic potentials. One of the hypotheses of the Spanish Flu was that it came from pigs (Nelson 2018), avian influenza from chickens caused outbreaks among humans multiple times (Yao 2019), the raising of cows might present less risk in thai category but they are also known to have spread zoonotic diseases such as cryptosporidiosis, E. Coli, ringworm, salmonella, and tuberculosis. But no known zoonotic diseases with similarly devastating effects were identified in the farming of fish and invertebrates. Probably most importantly, the feed conversion ratio of some fish and invertebrates can beat the 1.7-2.0 for chickens, or even fall below 1.

The important takeaway from this section is that in evaluating the economic and environmental reasons to replace animal products, we shouldn’t think that animal products = cows + chickens + pigs, and certainly not just cows, which seems to be some people’s impression.

It is important to point out that plants and plant-based foods are generally even more efficient than the raising of fish and invertebrates as food. Soy for instance is superior in many ways. But that is not the case for all plant crops. For instance, the farming of coffee and chocolate are both more carbon intensive than the meat of pigs, chickens, and fish. My intuition is that a lot of humans might want to live in an universe where at least some supply of coffee and chocolate exists despite their inefficiency in producing per weight of food.

II. Factory farming isn’t only about producing human food

Factory farming is often described as the raising of animals for human food such as meat, eggs, and dairy. While this is a big part that factory farming does now, it’s not the complete picture, and we shouldn’t assume that this part will continue to dominate the whole picture of factory farming. Humans also raise animals for making food for animals, fashion, pigments, medical supplies, experimentation, animals as pets and ornaments. These productions also experience pressure to reduce costs and increase the number of animals kept per space, they are often very much like the factory farming for meat, eggs, and dairy (sometimes exactly the same animals).

I am particularly concerned with one non-food use of farmed animals: harvesting organs. Some biotech companies are genetically engineering pigs to make their organs more compatible with the human body. But some scientists are trying to fully grow human organs in animals. This research, if successful, will prima facie increase human welfare. But it could have huge implications for animals as it will increase the likelihood of humans keeping factory farming around, and the number of farmed animals we will raise. The analysis in this paragraph alone increases my assigned probability that there will be factory farming of vertebrates on earth by 2x, and and 5x for scenarios where we expand beyond the earth. Also, this technology could be a reason that my guesstimates are all grossly underestimated.

The implications of this section for the long term is that even if the surge of superior ways to produce protein eliminate the need to use factory farming to produce protein for human consumption, there are still other reasons why we might have factory farming to produce animals for other uses.

The following three paragraphs are pretty optional, but if you are interested in gaining a rough sense of the possible order of magnitudes of the numbers for these sources of factory farming, it might be useful to read some currently existing examples. Take ornamental fish. In 2018, China produced (which means they didn’t count the ones that died before reaching markets) 5.35B ornamental fish (there are no figures for the number of fish existing at a certain point), which represents roughly 4 fish per human in China in 2018. This number might still rise in China with increasing wealth. But in the long-term perspective, the ratio could be much lower as keeping these fish seems more difficult during times of catastrophes, space traveling, and on terraformed planets and space structures, than in contemporary China. But it seems safe to think that humans have a significant chance of (i.e. >20%) raising at least 1 ornamental fish per year in the long run. If that is the case, then the number of animals that have to be farmed means that factory farming would be pretty much the standard set up to go. In expected value terms, the number of ornamental fish raised per human each year can be seen as 0.2.

Consider the use of silk worms to produce silk too. China produced 86,500 tonnes of silk in 2018. According to three sources, different breeds of silk worms, in different seasons, produce 0.22g to 5g of silk per worm. If we take it to be 5g, there are then 17.3B silkworms killed (to make silk each silk worm has to be killed, by boiling) in 2018 in China. But we cannot assume every countries demand silk as much as China. According to multiple sources, China produces roughly 70% of the worlds’ silk, making the estimate of the number of silk worms 24.7B. That means humanity killed roughly 3 silk worms per capita in 2018 according to the absolute minimum estimate. Considering that insect farming takes little space, water, feed, and energy, and is hypothesized to be doable in other planets, and also that it tends to be done not because it is efficient (in fact, it is one of the most inefficient fibers to produce) but because of its perceived cultural and artistic value, it is reasonable to expect that humans will still kill at least 0.1 silkworms per capita each year, in expected value terms, in the long run. But the estimate could be way off, for example if the ratio of people who practice Chinese culture shrinks dramatically, or that the research using silkworms to produce strong functional silk like spider silk becomes commercially successful.

III. Technologies, including AI, will make factory farming more efficient

It might be natural to think of factory farming to have a constant state of technology while technologies on PB/​CM will improve very quickly—this was my picture previously.

Many people know that a lot of universities and PB/​CM companies are receiving a lot of funding to develop their technologies, products, and market. But the same goes for the factory farming industry. Not only are meat companies very rich and spend a lot of money on R&D. Academia also contributes to technologies used in factory farming. In China, U.S., Netherlands, U.K., India, Brazil, there are universities that have departments or faculties that serve the factory farming industry. There are even universities in China and Japan that are named after “animal husbandry”.

There is currently a new technological trend in the factory farming industry, called “precision livestock farming”. I am now working with Peter Singer researching this development, and its moral implications. Short description of this trend: It is the use of sensors connected to the same computer or server (IoT), big data analytics, more recently the use of AI related technologies such as robotics and machine learning. Using machine learning, patterns such as body temperature, movements, sounds the animals make, or even their faces, can all be interpreted by AI systems to predict and detect diseases, injuries, parasites, model the growth rates, detect pregnancies, etc. These techniques aim at reducing the amount of feed and water used, reduce fatality rate, and increase stocking density.

Another technology that is helping the factory farming industry is bioengineering. Selective breeding techniques can select traits that make animal product production more efficient. For example, the growth rate of broiler chickens had doubled since the 1950s. Currently, there seems to be efforts to try to incorporate AI in this process (1, 2, 3), which industry people claim will make selective breeding much more powerful and quicker..

The analysis in this section casts major doubts that one of PB, CM, 3d printed meat (or their egg and dairy versions) will be superior to all animal products in every possible way, including but not limited to pure energy conversion terms.

IV. Sometimes inefficient things won’t simply disappear

This is probably a weak reason, but might still be worth considering. There seems to be a lot of evidence for this in our current generation. Silk, as we mentioned earlier, is one of the most energy and time inefficient ways to produce fibers. But it kept growing when people got wealthier. We also mentioned earlier that chocolate and coffee have even higher carbon intensity than the meat of fish, chicken and cow. But will humans eliminate the farming of coffee and chocolate entirely? Maybe, but I wouldn’t assign a 100% credence in this belief. And it seems to me that we shouldn’t do that for factory farming either. Some might counter-argue that chocolate and coffee are not just food items but they create enjoyment, but so do animal products for some people.

V. Factory farming might spread to space—Some proponents of space colonization include factory farming in their plans

This is probably the most important point from I to V, particularly regarding factory farming spreading to space.

Gerard O’Neill, in his 1974 paper The Colonization of Space, said “the colonies should be able to support 143 people per hectare with a diet of 3000 calories, 52 grams of usable protein and 4.3 pounds of total food per person per day [ref 9]. Much of the protein would come from poultry and pork.” He even consulted soil scientist Richard Bradfield, who told him that he “has grown enough to feed 72 people per hectare by the techniques of double planting and multiple cropping, and with the use of cuttings for livestock feed.” in an experiment done in the Philippines. Another early major space advocate, planetary scientist Thomas Heppenheimer, wrote in his book Colonies in Space (1977) about the methods of raising fish, rabbits, sheep, and egg laying hens on O’Neill’s cylinder type of space colonies.

It could be argued that cultivated meat was only a concept and plant-based meat was still very rudimentary and distasteful at their time, so they could be missing better options for feeding people. But let’s look at the more recent discussions.

Deep Space Food Challenge, a competition held by NASA and Canadian Space Agency, awarded 2 projects on insect farming in the Canadian branch, and 2 projects on insect farming plus 1 project on fish farming in the U.S. branch. The European Space Agency has a project called Lunar Hatch, looking to bring fish eggs to the moon and conduct aquaculture there. In academia, geologist Kevin M. Cannon, a proponent of space resource extraction, has a website eatlikeamartian.org and a paper Feeding One Million People on Mars, in both of which he proposed to use insect farming (along with cellular agriculture) to feed people’s need for protein. On the commercial side, a joint venture of SpaceX and CERN was announced in November 2018 it was said that “the first fish farms in Mars will be a fact in 2029.” I also find it amusing that a start-up in aquaponics (systems that combine plant agriculture on water, and fish farming) whose current target use scenarios are on earth, is called Terra Mars.

What should we do?

Honestly, I haven’t formed any views on interventions that can tractably affect the lives of farmed animals in the far future. More research on PB/​CM, and maybe shifting PB/​CM’s focus to replacing aquatic animal farming and competing with insect farming could be the way to go, but I feel too uncertain to make it a recommendation. The only kind of work I feel reasonably confident to recommend EAs to do is to do more research on this potentially important issue, probably refine or even re-do my whole analyses done in this post. I would also like to see an analysis of how this consideration might change current prioritization.


You might skip this part if you don’t want to read something that I didn’t use to form my views summarized in the tables. But these are thoughts that I had which I found interesting.

Bonus 1: Humans might find new animals on other planets, and they might factory farm them

The difficulty of transporting, bioengineering, adapting, and raising earth originated animals in space are reasons to be doubtful about its feasibility. But if we find new animals on other planets, the story might be totally different. This might be a minor consideration currently since the chance seems very low with current evidence. But I think this is worth listing out at least, so that future conversations on this might continue if we will update on this.

Bonus 2: The separation between farmed animals and wild animals might blur over time

The current distinction between these two types of animals are very clear. But as technologies advance, humans might directly manage what happens in “nature”, possibly down to molecular levels. This might be more likely if the “nature” was simply created by humans, on terraformed planets and space structures.

If wild animals live net negative lives, creating “new nature” in space might not be very different from factory farming. We bring them to life to fulfill our preferences, we manage them, we cause them enormous suffering. Whether we eat the corpses of the animals who suffered a lifetime of misery doesn’t really matter to me.

Update: Someone flagged that one of the links was actually an April’s fool—the SpaceX fish farm on mars. But the other projects on space factory farming are real, and the poster of the April’s fool seems to think that the joke is actually feasible.