In this post, I lay out some different ways of looking at what’s alive right now. 

This seems worth knowing about to me, but also hard to grasp because of how huge the numbers are. A lot of what I’m doing in the post is trying to find ways to get my human brain to understand big numbers about how the world is.

I don’t have a considered view on which organisms are sentient or how much, or on how much different organisms matter morally compared to other organisms.

Biomass

I like this graphic a lot:

It’s from Our World in Data article on Biodiversity and Wildlife [I recommend following the link so you can zoom in on the graphic], which pulls from a 2018 paper by Bar-On, Phillips and Milo.

Some of the headlines that OWID pull out:

The reason to look at life on earth in terms of biomass rather than individual organisms is an intuition that this makes it more comparable: otherwise the numbers get dominated by loads and loads of tiny things, and the bigger things (which most people care more about) barely show up.[1] 

Numbers

I’m still kind of interested in the absolute numbers though. I think this is partly because my brain is better at conceptualising ‘individual organisms’ than ‘weight in tonnes of carbon’.

Bar-On, Phillips and Milo do give estimates for the absolute numbers (which they call ‘abundance’), to the nearest order of magnitude:[2]

TaxonBillion tonnes of carbonAbundance
Total for subclassTotal for class
PlantsTrees 45010^13
BacteriaTerrestrial deep subsurface60 10^30
Marine deep subsurface7 10^29
Soil7 10^29
Marine1.3 10^29
Total 7010^30
Fungi  1210^27
ArchaeaTerrestrial deep subsurface4 10^29
Marine deep subsurface3 10^29
Soil0.5 10^28
Marine0.3 10^28
Total 710^29
Protists  410^27
AnimalsChordatesFish0.7 10^15
Livestock0.1 10^10
Humans0.06 10^10
Wild mammals0.007 -
Wild birds0.002 10^11
ArthropodsTerrestrial0.2 10^18
Marine1 10^20
Annelids0.2 10^18
Molluscs0.2 10^18
Cnidarians0.1 10^16
Nematodes0.02 10^21
Total 210^21
Viruses  0.210^31

(See also this post by Brian Tomasik for another set of estimates and much number crunching.)

I want to zoom in on the animals part of this table. First, for people who like me don’t intuit how big the difference between 10^10 and 10^18 is, here is the animals part of the same table with zeros:

ChordatesFish

1,000,000,000,000,000

Livestock

10,000,000,000

Humans

10,000,000,000

Wild mammals

-

Wild birds

100,000,000,000

ArthropodsTerrestrial

100,000,000,000,000,000

Marine

10,000,000,000,000,000,000

Annelids

100,000,000,000,000,000

Molluscs

100,000,000,000,000,000

Cnidarians

10,000,000,000,000,000

Nematodes

100,000,000,000,000,000,000

So for every one human, there’s something like 10 billion nematodes. 

The estimates Bar-On, Phillips and Milo give are orders of magnitude (which makes sense given how big most of the numbers are). For some of the smaller numbers, we can get more precise estimates. Here’s a table I made with some more numbers I was interested and able to find:

 Order of magnitude from Bar-On, Phillips and Milo EstimateYear
Fish1 quadrillion (a million billions)Farmed fish126.5 billion[3]2015
Wild fish999,873.5 billion (999.9 trillion)[4]-
Livestock10 billionPoultry25.7 billion[5]2018
Cows1.5 billion2018
Sheep1.2 billion2014
Goats1 billion2014
Pigs1 billion2018
Humans10 billion-8 billion2022
Wild mammals--550 billion[6]-[7]

My brain can track these numbers better than the raw orders of magnitude. But even smaller numbers would be even easier for me to make sense of.

One way of getting smaller numbers is to think about how many organisms of different types there are for every individual human. So for each human alive today, there are:

  • <1 cow, sheep, pig, and goat, respectively
  • ~3 poultry in farms
  • ~16 fish in farms
  • ~70 wild mammals
  • ~127,000 fish

What’s dying right now?

Another way of getting smaller numbers is to look at how many individual organisms die each year, or day, or minute. This is grim, and I feel a bit bad raising it, but it also seems important to have a sense of. Please skip this part if it’s too much for you.

The graph below shows an estimate for the number of deaths each minute, for humans and some kinds of farmed animals:

Deaths per minute, humans and some kinds of farmed animals

[Spreadsheet form here.]

That’s 2 people every second of every day.

Of the 116 humans who die each minute, roughly 2 have been deliberately killed by other humans. All of the fish, chickens, pigs, sheep and cows represented in the graph above are farmed animals who have been deliberately killed by humans.

Again, we can make these numbers smaller by asking how many deaths there are for each human death.

If I were to die in the next minute, more than 100 other humans would probably die with me. And in that minute, for each of those human deaths (including my own), the following animals would die:

  • 5 cows
  • 9 sheep
  • 25 pigs
  • 1,150 chickens
  • 1,800 farmed fish
  1. ^

    Brian Tomasik suggests that respiration might be an even better way of looking at life on earth, given that a lot of the biomass of trees is essentially dead. See here.

  2. ^

    On p. 89 of their supplementary materials.

  3. ^

    This is the midpoint of their range.

  4. ^

    This is just the order of magnitude minus the estimate for farmed fish.

  5. ^

    NB this is slightly lower than some estimates I've seen for just chicken populations. Not sure what's up with that.

  6. ^

    This is the midpoint of Tomasik's range.

  7. ^

    Post last updated in 2019; Tomasik is pulling from various sources and I don't think it makes much sense to give a year.

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Regarding whether to focus on numbers or biomass, I think the following articles  could be relevant:

Brian Tomasik's Is Brain Size Morally Relevant? explores arguments for brain-size/complexity weighting and for 'equality weighting' (equal consideration of systems). Despite the title, it's not just brain size that's discussed in the article but sometimes also mental complexity ("Note: In this piece, I unfortunately conflate "brain size" with "mental complexity" in a messy way. Some of the arguments I discuss apply primarily to size, while some apply primarily to complexity.").

The question of whether complexity matters is related to the intensity of experiences. Jason Schukraft's Differences in the Intensity of Valenced Experience across Species explores this and seems to conclude that for less familiar systems (well, animals -- I think only animals are explored in that piece) it's really unclear whether the "intensity range" is larger or smaller. They could potentially suffer more intensely. They could potentially suffer less intensely.

Another article by Brian Tomasik: Fuzzy, Nested Minds Problematize Utilitarian Aggregation raises the question of how to subset/divide physical reality into minds. Like Brian, the approach that's most intuitive for me is to "Sum over all sufficiently individuated "objects"" and count subsystems (e.g. suffering subroutines) too. Although, I think the question is still super confusing. It's also written in the article that "[p]erforming any exact computations seem intractable for now" although I don't know enough math to say.

I think it's ultimately all quite subjective though (which doesn't mean it's not important!). For me, I don't see how we can definitively show that some approach is correct. (Brian Tomasik describes this problem as a "moral question" and frames it as there's "[n]o objective answer" but I feel like his language is slightly confusing. Rather, I think there is an answer regarding suffering/sentience, but it's just that we might not ever have the tools to know that we've reached it. In the absence of those tools, a lot of what we're doing when saying "there's more suffering here" or "there's more suffering there" might be or might be compared to a discussion of morality.) We're also using a bunch of intuitions that were shaped by factors that don't necessarily guide us to truths about suffering/sentience (I explore this in the Factors affecting how we attribute suffering section in my recent microorganism post).

Thanks for writing this. Now I have a clearly-written, concise piece to share with people whenever I go on a rant about the absolutely absurd number of nematodes. (They're the average animal! By the numbers, Animalia is~worms!)

I had no idea there were this many nematodes—is wild animal welfare just nematode welfare?! Do Rethink, WAI, or others have any research on them?

They're surprisingly well-studied - I think because they have very simple & highly centralised nervous systems. I also liked this Microcosmos video on them :)

What's the significance of the two different columns under the heading "Billion tonnes of carbon" in the first table?  What does it mean for the number to be in one or the other?

I think the numbers on the right column are supposed to be the 'totals' of the biomass of the domains/kingdoms/viruses as entire groups.

The original table is on page 89 of the supplementary materials document of the Bar-On, Phillips, and Milo paper. 

Thanks Elias, I think you're right.

Isaac, I've tried to make this clearer in the table in the post.

[Also by happy chance this process made me notice that I'd lost all of my footnotes in the process of transferring from google docs, which I've now fixed. Thanks both for indirectly causing me to notice this.]

Thanks for writing this! The very last sentence seems off. Did you mean to say every second (instead of minute)? Also, the number of farm animals that die every second should be 1/60 (not 1/120) of that in the “minute” table above.

This last sentence was quite shocking for me to read. It’s sad…but very powerful.

Thanks for picking this up Wayne!

The mistake I made was number of people: it should have read 115 other people, not one. I did mean minute, and the number of animals is 1/116 to get a number of animals per human, rather than 1/60 to get a number of animals per second.

I've corrected the number now. (Thanks also to someone else who messaged me about the error.)

Got it. But I think the phrasing for the number of animals that die is confusing then. Since you say "100 other human [sic] would probably die with me in that minute," the reference is to how many animals would also do during that minute.  I think what you want to say is for every human death, how many animals would die, but that's not the current phrasing (and by that logic, the number of humans that would die per human death would be 1, not 100).

I'd suggest making everything consistent on a per-second basis as smaller numbers are more relatable. So  1 other human would die with you that second, along with 10 cows, etc.

I've changed the wording to make it clearer that I mean deaths per human per minute. I don't want to change it to second; for me dying in the next minute is easier to imagine/take seriously than dying in the next second (though I imagine this varies between people).

New phrasing works well!