Should Longtermists Mostly Think About Animals?

In this post, I explore some evidence that appears to indicate that total utilitarians sympathetic to longtermism should primarily focus on the effects of their actions on wild animals. I note that I am not particularly sympathetic to prioritizing existential risk reduction, nor do I subscribe to total utilitarianism. However, I am interested in these viewpoints, and am curious to understand how individuals who do subscribe to these perspectives perceive these arguments. If my arguments are correct, animal welfare seems like an important missing piece in the discussion of longtermism — Stijn Bruers has explored similar ideas, and Denis Drescher has discussed making wild welfare interventions resilient in case of civilization collapse, but otherwise I don’t think I’ve seen other analysis of the importance of animal welfare from a longtermist perspective. (Edit: Michael Aird pointed out that Sentience Institute’s research on moral circle expansion also is relevant here). The most relevant published research that is directly related to this topic is Simon Liedholm and Wild Animal Initiative’s work on intervention resilience.

I don’t personally believe that the highest priority should be animal-impacting existential risks in part because I am certain about total utilitarianism nor longtermism. But I do think that if you are both those things, and think it is plausible that many animals have welfare, taking animal welfare considerations seriously in longtermism should be a high priority. To write this piece, I’ve attempted to put on total utilitarian and longtermist hats. Based in part on the sheer number of non-human animals, I can’t see a way to avoid the conclusion that animal welfare dominates the considerations in utilitarian calculations. I welcome feedback on this argument, and to try to understand why total utilitarianism seems to primarily focus on future human welfare.


Animal welfare is frequently considered a short-term cause area within effective altruism. As an example of this, the EA Survey lists animal welfare as a separate cause area from the long-term future. A plausible reason for this conceptual separation is that most animal charities work on short-term issues, with perhaps the exception of wild animal welfare organizations.

However, separating animal welfare and longtermism as cause areas seems to neglect the fact that animals will likely continue to exist far into the future, and that if you think animals are moral patients then you ought to think that their welfare (or the lack thereof following their extinction) matters. Animal welfare should therefore be a consideration in evaluating the impact of existential risks and s-risks.

In fact, if one is a total or negative utilitarian, thinks that animal welfare is morally important, and buys arguments for strong longtermism, I argue that your primary focus ought to be on the welfare of wild animals over the very long-term. I argue that the vast majority of the value in preventing existential risks is either in preserving future animal life, or preserving human life in order to reduce wild animal suffering (depending on whether you are a total or negative-leaning utilitarian, and whether or not you think animals have on average net-positive lives). I also outline the beliefs that might lead one to dismiss wild animal welfare as the most important long-term cause area, and why I think that those beliefs are somewhat unreasonable to hold.

This is an exercise in imagining how many wild animals there are, and how many there will be. Even when I apply often used discounts to animal populations, my model suggests that animals overwhelmingly dominate total welfare considerations. The figures that I will present aren’t to be taken as exact estimates, but instead a demonstration of the degree to which animal welfare considerations should dominate human welfare for a total utilitarian, and potential scenarios in which that could change. There are probably lots of ways in which my figures and estimates could be improved, and I’d welcome any attempt to do so.

To what extent does animal welfare dominate?

Using a few discount rates, discussed below, we can estimate the ratio of adjusted animal welfare to human welfare, and the implied human population (or number of digital minds — see Notes) that would have to exist for human welfare to be the majority of total welfare. Using stable populations over time (i.e. assuming no population growth), we can estimate something like “number of equally weighted moral patients” and get a sense of whose interests dominate speculative welfare equations. The full model used to determine these figures is here, and comments on the populations and discounts discussed are in the Notes section.

Model details

To create this model, I first divided the animal kingdom into two populations:

ALL: Many animals that might be considered moral patients: mammals, birds, reptiles, amphibians, fish, cephalopods (squids, octopi, etc.), terrestrial arthropods (insects, spiders, etc.), and copepods (zooplankton). Note that this estimate does not include many animals considered to plausibly have welfare, such as marine arthropods like lobsters and crabs, as I didn’t have good population estimates available for those species and was limiting my time working on this. Including them would only bolster the points made in this piece, so their exclusion makes the figures slightly more conservative in scale.

VERTS: Vertebrates and cephalopods: mammals, birds, reptiles, amphibians, fish, and cephalopods. These are animals often cited as the most likely to have valenced experiences, and only using them thus gives a more conservative estimate.

Then, I subdivided each of these populations into three categories: no discounting for animal welfare relative to human, applying discounts based on likelihood of sentience, or applying both discounts for sentience likelihood and some other arbitrary “moral weight”. I refer to the first type of discount as a “welfare credence,” or the degree to which you are confident that an average member of a particular animal taxa is a moral patient. The second type of discount (moral weight) is the amount you discount that animal’s moral worth, for whatever reason. For example, one might think certain taxa are worth less inherently, or think that some kinds of animals feel a diminished amount of pain and pleasure — both these beliefs would be captured by moral weight. Welfare credence and moral weight are labeled WC and MW accordingly.

So, if you believe with 100% certainty that every single animal has welfare, and has moral value equal to a human or the ability to feel as good or as bad as a human, use the figures in the row labeled ALL. If you believe that most invertebrates don’t have valenced experiences, and that we should consider humans to be much more important than other animals, or that animals experience good or bad feelings to a lesser degree than humans, you can use the most conservative figures, VERTSWCMW.

Personally, I would use the ALLWC figures. The welfare credences implemented in the model are broadly inferred from the sentience credences estimated by some researchers at Rethink Priorities where available, and they account for a broad range of possibilities. Note, though, that I extrapolated the authors’ values to entire taxa, while Rethink Priorities only reviewed the literature on specific species of animals. I also entered my own based on what I perceive to be general perceptions for taxa that Rethink did not study. Also note that I assumed that having sentience is perfectly correlated with having welfare, which I think is generally safe to do.

As far as I can tell, Rethink Priorities’ work is the most rigorous attempt to establish credences of sentience. I also generally think that there have not been strong arguments made for using moral weights to discount the value of animals, or strong arguments made to suggest that animals feel less pain or pleasure than humans. Even if you think consciousness is on a gradation, in some meaningful sense, further argument would be needed to demonstrate that the gradation also indicates less strong feelings of pain or pleasure, or the capacity for welfare is diminished. For example, if pain is an evolved behavior to learn what to avoid, animals with lower problem solving abilities might need even stronger pain signals to internalize how to respond to various negative stimuli. This is just speculation, but regardless, I think a positive case needs to be made for discounting animals’ moral worth on the basis of mental ability alone. So, I lean toward not using the moral weight adjusted figures.

Various arguments have been made for and against moral weights, and there’s enough ground for discussion for an entire post of its own, so I will leave that question and simply say that regardless of which set of figures you apply, the argument that animal welfare dominates total welfare seems to hold, even with significant discounts on the basis of welfare credence and moral weight.

Animal numbers

Table 1, below, shows two comparisons of animal populations to human populations, but not animal populations themselves. The second column shows how many times larger total animal populations are compared to human populations (animal populations discounted as described above). The third column shows the required human population to have an equal amount of human and animal welfare in each of these scenarios. Note that in the most conservative estimate here, a total utilitarian would need there to be ~1.6 trillion humans for animal welfare to not dominate welfare considerations.

Special considerations for negative utilitarians

If you’re a negative utilitarian, you might be less concerned about potential welfare, and more concerned about how much suffering there will be. Obviously estimating wild animal suffering is tricky, but we could estimate how many instances of a frequently painful, and possibly particularly dominant experience there might be — total deaths.

Many animals are much shorter lived than humans. This means that not only are they greater in number, their entire population might die out many times over the course of a single human lifespan. We can’t just look at population size to estimate deaths over time. We can estimate it with something like “deaths per year” over time. Since in a stable population, this would be about the same as births per year, you could use fecundity data from a database like COMADRE, and calculate the deaths: D_x = D_0 + B*D_0*X where D_0 is the population of animals at time 0, B is the average number of births per individual per year, and X is the number of years you’re measuring.

While I didn’t complete this estimate for this piece, with some reasoning we can quickly see that animal deaths will outpace human deaths by a greater degree than animal welfare outweighs human welfare. Most animals are simply born more frequently than humans for a similar-sized population. B will be much higher for many animal populations, especially for small species with high population sizes, and therefore we can expect deaths per year in animals to dominate human deaths per year to an even greater degree than population size does.

From the table above and this reasoning, we can see that even when discounting liberally, animal welfare and plausibly suffering dominate human welfare and suffering. However, these numbers are just a snapshot of the present. Additional concerns are present for the future.

Could human welfare dominate animal welfare in the future?

For my estimation of the future, I assume that animals neither leave Earth, nor decline massively in population (averaged over the long run). This is obviously a risky assumption, but assuming that net-primary productivity does not change massively, such as a massive increase in human-appropriated NPP, and as animal body sizes probably take millions of years to change (in terrestrial mammals, for example, a 100-fold increase in size takes approximately 1.6 million years), it seems like a safe assumption for the future, even if at present we believe some animal populations are currently declining due to climate change caused habitat loss.

Using these assumptions, we can ask the following question: at reasonable human population growth rates, how long until human welfare or suffering (by this metric), overtakes animal welfare or suffering, if ever?

Of course, human population size will never reach anything near the numbers cited in the third column of the above table (Table 1) while humans are confined to Earth. My estimates assume that animals don’t join humans in space. If there will be a large-scale space colonization effort in the future, it seems unlikely that animals would not also colonize other planets along with humans. However, colonizing space without animals is the only realistic scenario where humans stand a chance to dominate total welfare considerations — most animals seem to be just much more efficient carriers of welfare than humans (in terms of mass per mind), and were we to settle any place to a large degree, it seems plausible that we’d also, actively or inadvertently, settle many more animals than humans, but this is pure speculation.

For growth rates, I used a range between 0.25% and 1.25% per year. The current population growth rate is about 1.08% per year, and it has been declining steadily for decades. Note that this is an average over the very long term, so unless we expect human population to explode, ideally the correct number will be in or below this range. My full calculations are at the bottom of this model.

Note that this continuous growth scenario seems unlikely. Human population on Earth is capped by resources, possibly below 10B people. In the solar system, it seems likely that for a long time, Earth will remain the primary home of humans, suggesting that no other planet will have greater than 10B humans. In the most conservative case, where we only count vertebrates and cephalopods as having moral weight, discount their experiences heavily, and use the lower bounds on our estimates of population size, there would need to be around ~160 locales with 10B humans for their welfare potential to match that of the animals on Earth alone. Of course, this still assumes that these 170 new colonies have no animals, making this situation increasingly dubious. Additionally, for their argument in favor of longtermism, Hilary Greaves and Will MacAskill assume a per-century human population of 10 billion, and assume a total human population (in expectation) over the future to be 10^15 , a notably smaller number than even many of my estimates (see Table 1) of welfare confidence and moral weight adjusted animals alive today.

Regardless, say human population was going to just grow continuously — how long would it take at the stated rates to dominate animal welfare?

Under this model, even if the vast minority of animals have moral significance, and we discount those animals’ welfare heavily, and we think human population growth will proceed at an extremely high 1.25% rate indefinitely, human welfare potential will not dominate animal welfare for a minimum of ~500 years. Of course, another possibility is that human population will never reach the 1.7T required for human welfare to overtake animal welfare as being of dominant concern. Or, it will take far longer than the upper limit of 9400 years if human population growth becomes much lower or stalls entirely. Of course, all of the foregoing analysis assumed that animals will not accompany humans to space. However:

Space colonization will probably include animals

Since the populations of humans that are required for animal welfare to no longer be of dominant concern to a total utilitarian seem likely to be over 1 trillion, the space colonization required to sustain such a large population would probably involve large scale terraforming or free floating space settlements. It seems possible that these habitats would have animals, especially if they reach the scale needed for human welfare to dominate (i.e. a human population of ~1.6T). While the figures above assume animals will remain on Earth, even a small chance that they join humans in space means that it would be unlikely that human welfare will ever dominate animal welfare, or that the expected value of acting solely to benefit humans will ever outweigh acting to help animals.


If you are a longtermist, a total utilitarian, and believe that at least some animals have valenced experiences, these figures ought to incline you toward the following beliefs:

  • If you think animals on average have net-positive lives, existential risks to animals are vastly more important to prevent than x-risks that just impact humans. In fact, x-risks that eliminate human life, but leave animal life unaffected would generally be almost negligible in value to prevent compared to preventing x-risks to animals and improving their welfare. Additionally, not only should your primary focus be on preventing x-risks to animals, you ought to work to ensure that animal welfare is highly resilient.

  • If you think animals on average have net-negative lives, the primary value in preventing x-risks might not be ensuring human existence for humans’ sake, but rather ensuring that humans exist into the long-term future to steward animal welfare, to reduce animal suffering, and to move all animals toward having net-positive lives.

  • Whether or not you think animals have positive or negative lives overall, you still ought to think that the primary impact of x-risks will be reducing humanity’s ability to improve the lives of animals, and that x-risks only impacting humans are of much less concern (such as, an advanced pro-welfare AI that eliminates humans but takes great care of animals).

  • Additionally, you might be inclined against fostering human welfare into the far future without fostering concern for animal welfare, as that risks future humans not acting appropriately to preserve wild animal welfare.

If you are a longtermist and a negative utilitarian, and believe that at least some animals have valenced experiences, these figures ought to incline you toward the following beliefs:

  • The primary motivation for preventing x-risks ought to be ensuring humans exist to steward animal welfare, and decrease animal suffering.

  • The s-risks of greatest medium-term concern could be dramatic changes in animal populations, such as space colonization that includes animals, or changes in Earth’s environment leading to smaller animals that trap fewer resources in their bodies.

And, no matter your particular brand of utilitarianism, you ought to be inclined toward supporting wild animal welfare research and work, and support designing and implementing resilient, cost-effective interventions to reduce wild animal suffering.

Beliefs that might lead one to disagree with these conclusions

Discounting or rejecting animal welfare to an extreme degree

You could plausibly make a case that human welfare should dominate the calculations by demonstrating that we ought to discount animal lives to a much greater degree than I did in the model. The welfare credences I used were generally inferred from Rethink Priorities’ work and my own sense of how people view various taxa, and the moral weights were somewhat arbitrary but seemed reasonable. I haven’t seen a better attempt than Rethink Priorities’, so setting welfare credences aside, I’ll explore objections to my moral weights.

First off, it’s worth pointing out that even under the scenario in my model in which human population is the greatest percentage of adjusted animal population, it is less than 0.5% of the total. This scenario already completely removed invertebrates (besides cephalopods) from the equation, and discounts animals like fish, mammals, and birds heavily. So, at a minimum, if you believe my moral weights are too high, you need to believe that they are 200x too high for expected human welfare to equal animal welfare.

Further progress toward human welfare supremacy might be made by removing fish, by far the most numerous in our restricted category, from the equation, but this would seem to go against a growing scientific consensus that fish are sentient and feel pain. Arguments for moral weights seem dubious at best, but even looking at classic reasons given for believing in them, such as human’s high brain to body mass ratio, we ought to expect many smaller animals like fish, and rodents to perform at least as well as humans.

It seems like utilitarian and longtermist views that hinge on believing animals deserve very little moral consideration need to build a very strong case for heavy discounts via moral weights for animals or otherwise remove animals from consideration. I haven’t seen such a justification, although I would welcome an attempt. I suspect that making such an argument will be really difficult, but this is just based on what I perceive to be the general weakness of the approaches that have been offered before. Because no one has rigorously tried, I don’t think that I can offer a good critique of the concept outside of generalized suspicion of arbitrary discounts and the belief that given the apparent evidence that animals feel pain, we ought to take their welfare seriously.

Belief in high likelihood of extreme human population growth

Another reason to think that animal welfare shouldn’t be the main consideration in evaluating and reducing existential risks would be if you thought that human population was likely to suddenly grow enormously (and simultaneously that the likelihood of x-risks during the growth phase was low). If you think x-risks are at least somewhat likely in the near future, this growth would have to happen sooner or be much faster. Then you might expect human population to soon overtake our welfare credence and moral weight adjusted animal populations, and human welfare to matter more than animal welfare.

Of course, for the reasons I mentioned in a previous section, this seems unlikely to happen in near future timescales due to resource constraints, unless we were able to simulate very large numbers of minds. This is outside my area of expertise, and I’d be interested in reading speculation on the future of human population size, but reaching a population of over 1 trillion without also increasing animal populations strikes me as extremely unlikely, and were it to happen, it would be an event that would not happen for an extremely long time.

Belief that wild animal populations will massively decline or disappear entirely

My model assumed that animal populations would basically stay around the same size they are today for the indefinite future. This is probably unlikely, but given that I don’t know whether or not they will grow or shrink, it seems reasonable that the best bet is that animal populations will on average, be about the same size they are now.

There might be a few reasons that you think animal populations will decline massively. The first would be that a major event (like climate change or human caused habitat destruction), will decrease populations. Of course, animal species are shrinking in number at an alarming rate currently, and some populations are also decreasing (such as insects in some regions, or birds in others). But climate change is having the opposite effect on other animals, including squids. There isn’t yet reason to believe that overall animal populations are decreasing. And, given that animal populations recovered following a massive asteroid strike 66 million years ago, there isn’t any particular reason to think that the current round of climate change and animal habitat loss will reduce animal populations in the long term.

Another reason you might think animal populations will decline is that humans might intentionally reduce them. Perhaps this would be due to trying to limit suffering in the wild, or for other reasons. But doing this could actually be really difficult. Humans could take measures to encourage animals to trend toward larger sizes, or try to reduce or appropriate net-primary productivity. But regardless, given the near certainty that animal populations will continue existing for the time being, it seems odd to consider this a primary objection to this argument.

Rejecting total utilitarianism or longtermism

One other way to reject these conclusions would be to either reject total utilitarianism, in which case you might not think welfare is additive or comparable in the ways described above, or not think that we ought to focus on doing the most good on the margin. Or, you might reject arguments for longtermism, and argue we should focus on the present or near future. But even if you are a total utilitarian, “short-termist”, and think animals have experiences, the same evidence presents you with overwhelming reason to prioritize animals in the present unless you reject total utilitarianism as well.

Tractability concerns

Finally, you might be concerned that addressing wild animal welfare is intractable. This strikes me as too broad of a statement to be particularly meaningful, and one that needs to be nuanced and specify specific populations. However, even if taken as a whole, it doesn’t give us reason to not prioritize preventing x-risks that pose specific threats to animals over those that only pose threats to humans. And, longtermism as a whole is justified based on the value that the future might hold, despite it being difficult to affect it. The point I’m trying to make in this piece is not that this argument is wrong, but that the value is even greater than previously described. So, if you think we ought to work on the long-term future, this might incline you toward thinking the future is even more valuable, and that our priorities in addressing future wellbeing should be animal-focused.


Discounting animal lives

This piece discusses two kinds of discounts for animal lives — welfare credence discounts and moral weight discounts. Neither of these are related to the idea of discounting future beings, which is often (seemingly rightfully) dismissed in discussions of longtermism.

Below, I define these two terms, comment on how I arrived at the numbers that I used, and then discuss their overall impact on this analysis.

Welfare credence discounting

Welfare credence discounting is a discount to an animal’s moral worth, using expected value calculations, on the basis of one’s confidence that it has welfare. For example, I may be 100% certain (or 99.999% certain), that a fellow human has welfare, 95% certain that my dog has welfare, and 50% certain that a random fish has welfare. If I’ve got one room with 3 people, and another with a fish, my dog, and a human in it, I can say that the total number of welfare in each room might be 1*.99999 + 1*0.99999 + 1*0.99999 = 2.99997 moral patients in the first room (or basically 3), while in the other has 1*0.99999 + 1*0.95 + 1*0.5 = 2.44999 moral patients.

This suggests that there is a bit more capacity to do good in the first room. Maybe if I give all 3 people in that room an equally good experience, I’m fairly confident I’ve created the equivalent of 3 units of good (the exact units of good is not important here), while in the other room, giving 3 equally good experiences, I only expect to create 2.45 units of good.

Welfare credence might be determined by looking at the physiological, morphological, and behavioral features of an animal you expect to indicate the potential for having welfare, and then comparing it with an animal you have a lot of confidence in (like a human). So, if ants consistently avoid painful stimuli after experiencing it for the first time, that’s slightly more evidence to believe ants feel pain. You might try a variety of tests of relevant features and behaviors, and if the ant keeps passing your tests, your confidence in it having a welfare should grow. Rethink Priorities has explored this topic at length.

Another method for establishing a welfare credence might be using something like how much empathy you feel for various animals or people. This seems like a worse method to me, but it is another approach that some people have defaulted to.

For this paper, I generally used the approximate welfare credences produced by Rethink Priorities for various animal species, generalized across taxa. This is not a particularly precise method, and the generalization is risky, but given the lack of better information on invertebrate sentience, for example, it seems like a good place to start.

Moral weight discounting

Another concept often discussed in EA is discounting based on the “moral weight” of an animal. I personally think that this concept is fairly incoherent, or at least poorly defined. While it can be formally described in a variety of ways, I used single discount rates that are fairly arbitrary, but seem conservative and something most utilitarians who think animals matter morally might accept.

Moral weight seems to be used to refer to a few different things. One is just a sentiment like “animals deserve less consideration,” and discounting appropriately on grounds external to the animal. Another would be something like “animals have diminished mental abilities, and therefore less capacity for welfare.” This would be a claim like: humans feel in the range −1 to +1, while dogs, for example, feel only in the range −0.1 to +0.1. Therefore a dog has ~1/​10th the moral worth of a human.

The second of these definitions seems like the more coherent, but also seems to break down when scrutinized. The usual reasons that are given that animals might have less moral weight are things like “they have fewer neurons,” “they have a lower brain to body mass ratio,” or “they have a lower square root of the brain to body mass ratio” and scaling to that root accordingly (usually never explaining why morality would magically scale to the root of a random physiological features). While none of these explanations seem to have any root in science or ethics, and frequently don’t leave humans at the top (which I assume is the motivation behind them), they still are widely stated.

I think the most coherent description I’ve heard of why animals could have lower moral weight or diminished welfare in a meaningful sense is that as a matter of history, consciousness evolved, and probably the first beings that were conscious were “less conscious” in some meaningful sense than humans today. This is interesting, though it doesn’t necessarily imply that those animals felt, for example, significantly less pain from painful experiences. And, it is important to note that all (or most) animals living today have been evolving since those first animals, and have had just as long as humans to develop consciousness (~900 million years ago, neuronal genes were present in some single celled individuals, millions of years prior to the oldest macroscopic animal fossils, which themselves are from prior to the Cambrian explosion). Ants and their progenitors have had neurons for the same amount of time as humans and hominids, and have had the same amount of time to develop consciousness as humans. Our common ancestor with ants likely had neurons too. The fact that animals that existed at the beginning of consciousness’s evolution might have had diminished consciousness isn’t necessarily evidence that animals today do, or evidence that they had less moral worth.

Additionally, there is some reason to think diminished consciousness might actually lead to more moral worth. Perhaps animals that have worse pattern recognition or puzzle solving ability need stronger motivation to avoid negative stimuli, and feel even worse pain, for example. Applying moral weights strikes me as needing a lot more justification than just neuron counts, or something similar.

Another note is that even if you think my moral weights are too high, for human welfare in expectancy to equal total animal welfare you’d need to think they are 200x too high. This to me strikes me as an unreasonably high discount to apply to the many animals who do seem to feel positive and negative experiences strongly.

But, because there is widespread belief in moral weights, I applied the above weights in some of the estimates.

Animal groupings

I used the following groups of animals in my analysis:

  • Mammals

  • Reptiles

  • Birds

  • Amphibians

  • Fish

  • Cephalopods (squids, octopi, nautilii, cuttlefish)

  • Terrestrial Arthropods (insects, spiders, etc)

  • Copepods (most zooplankton)

This group is referred to as all ALL (all animals).

I also created a subpopulation without animals that are frequently considered to not have welfare — terrestrial arthropods and copepods. This group is referred to as VERTS (vertebrates, though it includes cephalopods, since many believe squids and octopi to have welfare).

Finally, I assigned a range of welfare confidences (WC) and moral weights (MW) to these groups (outlined above).

Then, I estimated populations for both ALL and VERTS using pure animal numbers (e.g. you believe all animals have a moral weight of 1 and are completely confident in that), discounting only for welfare confidence, and discounting for both moral weight and welfare confidence.

This gives us 6 populations, called respectively:



As I conclude in my summary, my argument seems to hold for all 6 groups, though to different degrees. The most conservative estimate is VERTSWCMW. My opinion is that the most meaningful numbers are ALLWC.

There is also an additional population, called humans. This is the number of humans alive today (~8 billion). The human population is never discounted.

Animal populations and assumptions

While there is a lot of uncertainty on total wild animal populations, Brian Tomasik’s estimates seem reasonable enough to use as a starting point for this exercise. The uncertainty on population lowers the confidence in this argument a bit.

For this exercise, I used Brian’s estimates on the following taxa and groups of animals: humans, mammals, birds, fish, reptiles, amphibians, terrestrial arthropods, and copepods. I don’t use his estimates for a variety of other taxa for various reasons. For long-term purposes, I assumed animal farming and testing will end soon, so removed the livestock and lab animal estimates. I also didn’t use the numbers for coral polyps, rotifers, gastrotrichs, and nematodes since the chances they have valenced experiences might be low, and relatedly, am not using Tomasik’s estimates of bacteria populations for the same reason.

Note that recently, some have argued Tomasik’s estimates of bird and mammals are too high. Since in all of my estimates, this makes a fairly small difference in the totals, I chose to just use Tomasik’s numbers, though would welcome someone to make a copy of my model with more conservative population estimates.

Also, note that Tomasik does not have estimates for the populations of some molluscs and crustaceans that some consider to have experiences — cephalopods, gastropods (snails and slugs), and decapods (lobsters, crabs, prawns, and shrimp). There are also a variety of other animals left out of these estimates — aquatic insects, for example. Note however that given that it’s possible the animals not included have welfare, their inclusion would only make the conclusions of this piece stronger, so for the time being I’m exclusively using animals where attempts have been made at estimating population, with the exception of cephalopods, whose populations I estimated myself. Below are outlines of how I estimated cephalopod populations. I didn’t estimate gastropod and decapod populations because I didn’t easily find figures to use quickly to do so, and the argument stands without them.

Cephalopod population estimate

I used biomass estimates to get a quick sense of the number of cephalopods. For mass, I generally used the mass of the young, though the biomass would likely change throughout the year depending on the number of juveniles.

I don’t think this estimate is particularly accurate, as it is much smaller than the number of fish by several orders of magnitude. But, I suspect that the cephalopod population is at least 190B to 1.9T individuals. My math can be found here.

Digital welfare

Some have expressed concern that most future suffering (and most s-risks) will primarily affect digital minds, and not organic ones. If it were the case that digital mind were possible, the same populations of digital minds would be required as human minds (discounted if appropriate) for digital minds to be of predominant concern. I don’t try to assess whether or not this seems likely. My intuition is that it isn’t, but I don’t have particularly strong reasons for believing that — I’m mostly just not well read in this area.

Cephalopod population estimate sources

Boyle, P. (2001) Cephalopods. Encyclopedia of Ocean Sciences. pp. 524–530. doi: 10.1016/​B978-012374473-9.00195-8.

Domingues, P., Sykes, A., Sommerfield, A., Almansa, E., Lorenzo, A., Andrade, J. (2004). Growth and survival of cuttlefish (Sepia officinalis) of different ages fed crustaceans and fish. Effects of frozen and live prey. Aquaculture, 229:1–4, (239–254).: doi: 10.1016/​S0044-8486(03)00351-X.

Foskolos, I., Koutouzi, N., Polychronidis, L., Paraskevi, A. Frantzis, A. (2020). A taste for squid: the diet of sperm whales stranded in Greece, Eastern Mediterranean. Deep Sea Research Part I: Oceanographic Research Papers. 155: 103164. doi: 10.1016/​j.dsr.2019.103164.

Huang, C.Y., Kuo, C.H., Wu, C.H., Ku, M.W., Chen, P.W. (2018) Extraction of crude chitosans from squid (Illex argentinus) pen by a compressional puffing-pretreatment process and evaluation of their antibacterial activity. Food Chemistry. 254 (217-223). doi: 10.1016/​j.foodchem.2018.02.018.

Sinclair, E. H., Walker, W. A., & Thomason, J. R. (2015). Body Size Regression Formulae, Proximate Composition and Energy Density of Eastern Bering Sea Mesopelagic Fish and Squid. PloS one, 10(8), e0132289. doi: 10.1371/​journal.pone.0132289.


Thanks to Simon Eckerström Liedholm, Luke Hecht, and Michelle Graham for feedback, editing, and assistance with math.