Summary

• I would say the total welfare of soil animals is overdetermined to be much larger than that of farmed invertebrates in absolute terms. The individual welfare per animal-year of soil ants and termites should not differ much from that of farmed invertebrates, and I calculate the population of soil ants and termites is 3.93 M times that of farmed black soldier fly (BSF) larvae and mealworms, and 652 k times that of farmed shrimps.
• Projects targeting soil animals receive way less funding than ones targeting farmed invertebrates. The Wild Animal Initiative (WAI) granted 460 k$ to projects targeting invertebrates until 7 November 2025. In contrast, the Shrimp Welfare Project (SWP) received 2.9 M$ in 2024.
• I believe interventions changing land use can increase welfare much more cost-effectively than ones targeting farmed invertebrates accounting for effects on soil animals. I estimate funding the Centre for Exploratory Altruism Research’s (CEARCH’s) High Impact Philanthropy Fund (HIPF), which I calculate increases agricultural land by 1.29 k m2-years per $, changes the welfare of soil ants, termites, springtails, mites, and nematodes 3.43 k times as cost-effectively as SWP’s Humane Slaughter Initiative (HSI) increases the welfare of shrimps.
• I recommend research on the welfare of soil animals in different biomes over pursuing whatever land use change interventions naively look the most cost-effective. I have little idea about whether funding HIPF, or any other way of changing land use increases or decreases welfare. I am very uncertain about what increases or decreases soil-animal-years, and whether soil animals have positive or negative lives.
• There is no escape from the uncertainty of the effects on soil animals if one wants to increase animal welfare accounting for all animals. I do not know about any interventions which robustly increase animal welfare due to dominant uncertain effects on soil animals. I conclude electrically stunning farmed shrimp changes the welfare of soil animals more than it increases the welfare of shrimps if it results in the replacement of more than 0.0374 % of the consumption of the affected farmed shrimp by farmed fish. I can easily see this happening for even a slight increase in the cost of shrimp.
• I know about one project proposal for researching the welfare of soil animals. It is not public, but it will most likely start next year. I hope there will be more related projects. You are welcome to fill this very short form if you are interested in funding research informing how to increase the welfare of soil animals.

The total welfare of soil animals is much larger in absolute terms

As illustrated below, I estimate the absolute value of the total welfare of soil animals is much larger than that of farmed invertebrates for individual welfare per animal-year proportional to “number of neurons”^“exponent of the number of neurons”. In the graph below, 1E+N means 1*10^N. For example, 1E+2 means 1*10^2 = 100. For my preferred exponent of the number of neurons of 0.5, the absolute value of the total welfare of soil ants, termites, springtails, mites, and nematodes is 2.04 billion (= 9.77*10^5/(4.80*10^-4)) times that of farmed BSF larvae and mealworms, and 3.46 M (= 9.77*10^5/0.282) times that of farmed shrimps.

Animals with fewer neurons matter more for a low exponent. Holding the quality of living constant, for an exponent of:

• 0, all animals have the same individual welfare per animal-year.
• 0.5, the number of neurons has to become 100 (= 10^(1/0.5)) times as large for the individual welfare per animal-year to become 10 times as large.
• 1, the individual welfare per animal-year is proportional to the number of neurons, such that the number of neurons has to become 10 times as large for the individual welfare per animal-year to become 10 times as large.

As illustrated below, an exponent of 0.188 explains pretty well the welfare ranges in Bob Fischer’s book about comparing animal welfare across species, which contains what Rethink Priorities (RP) stands behind now. The blue dots are the welfare ranges from Bob’s book, and the red line represents the estimates for welfare ranges proportional to “number of neurons”^0.188. Shrimps have 9.30*10^-7 times as many neurons as humans, and are estimated to have a welfare range of 8 % that of humans in Bob’s book, and of 7.36 % that of humans for welfare ranges proportional to “number of neurons”^0.188.

Individual welfare per animal-year might approach 0 much quicker once the number of neurons drops below a certain threshold. Bryan Caplan sets this threshold between cows and humans. Many in the effective altruism community may set it somewhere between nematodes and shrimp. I worry people are coming up with arbitrary thresholds which support their preexisting views. The above power law of the number of neurons explains the welfare ranges in Bob’s book pretty well over 6.03 (= -LOG10(9.30*10^-7)) orders of magnitude (OOMs) of the number of neurons. I calculate the number of neurons of soil nematodes, the soil animals with the fewest neurons, is 8.55 (= -LOG10(2.79*10^-9)) OOMs lower than that of humans. So a power law from soil nematodes to humans only covers 1.42 (= 8.55/6.03) times as many OOMs of the number of neurons as one from shrimps to humans.

In any case, I estimate the absolute value of the total welfare of soil animals is much larger than that of farmed invertebrates even if all soil animals with fewer neurons than shrimps had a total welfare of exactly 0. I calculate soil ants and termites have 2.91 (= 250*10^3/(86.0*10^3)) and 1.16 (= 100*10^3/(86.0*10^3)) times as many neurons as shrimp, so they would still matter. For my preferred exponent of the number of neurons of 0.5, I estimate the absolute value of the total welfare of soil ants and termites is 14.0 M (= 6.74*10^3/(4.80*10^-4)) times that of farmed BSF larvae and mealworms, and 23.9 k (= 6.74*10^3/0.282) times that of farmed shrimps.

I would say the total welfare of soil animals is overdetermined to be much larger than that of farmed invertebrates in absolute terms. The individual welfare per animal-year of soil ants and termites should not differ much from that of farmed invertebrates, and I calculate the population of soil ants and termites is 3.93 M (= 1.50*10^17/(3.82*10^10)) times that of farmed BSF larvae and mealworms, and 652 k (= 1.50*10^17/(2.30*10^11)) times that of farmed shrimps.

Projects targeting soil animals receive way less funding

Projects targeting (optimised for increasing the welfare of) soil animals receive way less funding than ones targeting farmed invertebrates. I am not aware of any ongoing project targeting soil animals. More broadly, WAI granted 460 k$ to projects targeting invertebrates until 7 November 2025, although I got no results for “springtail”, “mite ”, and “nematode”, the most abundant soil animals, on their grantees page. In contrast, SWP received 2.9 M$ in 2024. I think they are the organisation receiving the most funds targeting farmed invertebrates.

Interventions changing land use can increase welfare much more cost-effectively than ones targeting farmed invertebrates

Increasing welfare as much as possible per $ need not imply targeting the animals with the most total welfare in absolute terms, and whose projects account for the least funding. However, I believe interventions changing land use can increase welfare much more cost-effectively than ones targeting farmed invertebrates accounting for effects on soil animals. For my preferred exponent of the number of neurons of 0.5, I estimate funding HIPF, which I calculate increases agricultural land by 1.29 k m2-years per $, changes the welfare of soil ants, termites, springtails, mites, and nematodes 3.43 k (= 70.6*10^3/20.6) times as cost-effectively as HSI increases the welfare of shrimps. I estimate funding HIPF changes the living time of soil animals by 5.07 billion animal-years per $, whereas I concluded HSI helps 15.0 k shrimps per $.

I recommend research informing how to increase the welfare of soil animals

I recommend research informing how to increase the welfare of soil animals over pursuing whatever land use change interventions naively seem to achieve that the most cost-effectively. I have little idea about whether funding HIPF, or any other way of changing land use increases or decreases welfare. I am very uncertain about what increases or decreases soil-animal-years, and whether soil animals have positive or negative lives. Research on the welfare of soil animals in different biomes would decrease the uncertainty about which land use changes increase their welfare.

Some may argue any attempts to research the welfare of soil animals are hopeless. I do not see how one can be so confident of this. There have hardly been any such attempts.

There is no escape from the uncertainty of the effects on soil animals

Lots of research may be needed before there are robust recommendations about how to increase the welfare of soil animals. Nevertheless, there is no escape from the uncertainty of the effects on soil animals if one wants to increase animal welfare accounting for all animals. I do not know about any interventions which robustly increase animal welfare due to dominant uncertain effects on soil animals. For my preferred exponent of the number of neurons of 0.5:

• I reckon GiveWell’s top charities change the welfare of soil ants, termites, springtails, mites, and nematodes 610 k times as much as they increase the welfare of humans.
• I calculate decreasing the consumption of chicken changes the welfare of soil ants, termites, springtails, mites, and nematodes 83.7 k times as much as it increases the welfare of chickens.
• I estimate cage-free welfare reforms change the welfare of soil ants, termites, springtails, mites, and nematodes 1.15 k times as much as they increase the welfare of chickens.

I suspect electrically stunning shrimp is one of the interventions outside research which more clearly increases welfare, as it narrowly focuses on decreasing pain during slaughter. Nonetheless, I still do not know whether it increases or decreases animal welfare due to dominant uncertain effects on soil animals. For my preferred exponent of the number of neurons of 0.5, I determined electrically stunning shrimp increases the welfare of these by 0.00144 QALY/shrimp. There are 94.3 shrimps per shrimp-kg. So I infer electrically stunning shrimp increases the welfare of these by 0.136 QALY/shrimp-kg (= 0.00144*94.3). For my preferred exponent of the number of neurons of 0.5, I estimate replacing farmed shrimp with farmed fish changes the welfare of soil ants, termites, springtails, mites, and nematodes by 364 QALY/shrimp-kg (= 522 - 158). So I conclude electrically stunning farmed shrimp changes the welfare of soil animals more than it increases the welfare of shrimps if it results in the replacement of more than 0.0374 % (= 0.136/364) of the consumption of the affected farmed shrimp by farmed fish. I can easily see this happening for even a slight increase in the cost of shrimp. Moreover, there are 3*10^29 soil bacteria, 613 M (= 3*10^29/(4.89*10^20)) times as many as soil nematodes (the most abundant soil animals). I would not be surprised if the effects on soil bacteria were much larger than those on soil animals, which further contributes to my very large uncertainty about whether electrically stunning shrimp increases or decreases welfare.

Interested in funding research informing how to increase the welfare of soil animals?

I know about one project proposal for researching the welfare of soil animals. It is not public, but it will most likely start next year. I hope there will be more related projects. You are welcome to fill this very short form if you are interested in funding research informing how to increase the welfare of soil animals.

Acknowledgements

Thanks to Anonymous Person for feedback on the draft. The views expressed in the post are my own.