Hi Michael. Thanks for sharing your thoughts.

I don't think welfare interventions targeting vertebrates will necessarily look worse than doing nothing on "Avoiding the worst" views, because they don't specifically, AFAIK, increase the risks of worse cases than inaction.

Interventions which cost-effectively increase the welfare of vertebrates will change land use much more than inaction, and a greater change in land use increases the probability of causing lots of suffering? Are you assuming that i) such interventions would increase agricultural land, and that ii) this decreases suffering?

On i), such interventions may decrease agricultural land due to increasing the price of animal products, and therefore decreasing their consumption? I estimate that replacing Ross 308 (fast growth broiler breed) with Rebro (slower growth) decreases cropland by 0.102 m²-year/Ross-308-chicken-kg, and that replacing replacing eggs from battery cages with those from barns or aviaries decreases cropland by 0.529 m²-year/battery-cages-egg-kg. These estimates neglect increases in the consumption of other foods, but I believe accounting for this would increase uncertainty, and therefore further increase the risk of the worst outcomes.

On ii), increasing agricultural land may increase suffering by increasing the number of soil macroarthropods/nematodes? I think effects on these may dominate (given the large uncertainty about welfare comparisons across species), and they may have negative lives (although I can easily see them having positive lives too).

Hi Laura. Thanks for the reply. I very much agree effects on soil invertebrates resulting from land use changes have very uncertain magnitude and direction. However, they should not be neglected under the types of risk aversion you studied?

1. “Avoiding the worst” risk aversion: All else equal, we are averse to the worst states of the world arising and want to take actions that prevent them or lessen their badness.
2. Difference-making risk aversion: All else equal, we are averse to our actions doing no tangible good in the world or, worse, causing harm.
3. Ambiguity aversion: All else equal, we should be particularly cautious when taking actions for which the probabilities of the possible outcomes are unknown and quite uncertain. 

"world" in 1 and 2, and "possible outcomes" in 3 should include effects soil invertebrates?

Do you agree that cage-free campaigns for laying hens may decrease the welfare of soil invertebrates much more than they increase the welfare of chickens, thus decreasing animal welfare a lot? I think this is very much on the table (although I can also see the effects on soil invertebrates being negligible). So I believe inaction is better than such campaigns for a sufficient level of “avoiding the worst”, or difference-making risk aversion. In addition, I infer inaction is better for a sufficient level of ambiguity aversion because the effects on soil invertebrates are very uncertain.

Here is a related comment from @Michael St Jules 🔸.

If we give extra weight to net harm over net benefits compared to inaction, as in typical difference-making [and "Avoiding the worst"] views, I think most animal interventions targeting vertebrates will look worse than doing nothing, considering only the effects on Earth or in the next 20 years, say. This is because:

1. there are possibly far larger effects on wild invertebrates (even just wild insects and shrimp, but also of course also mites, springtails, nematodes and copepods) through land use change and effects on fishing, and huge net harm is possible through harming them, and
2. there's usually at least around as much reason to expect large net harm to wild animals as there is to expect large net benefit to them, and difference-making gives more weight to the former, so it will dominate.

Hi Hans. I wonder whether the bulls may have positive lives despite the suffering they experience in the bullfights. In addition, the effects of producing their feed on soil invertebrates may be much larger or smaller than the effects on the bulls. I estimate that producing 1 kg of beef changes the living time of soil invertebrates by 1.39 billion animal-years, and of soil arthropods by 27.8 M animal-years.

@NickLaing, I am tagging you because I just updated this comment.

I suspect they will have a similar answer about soil invertebrates

Nitpick. I think you meant "about any soil invertebrates" or "about soil macroarthropods", as they have already commented on soil nematodes and microoarthropods (which are soil invertebrates).

we will see

I am not sure. I made a related comment 2 months on the post Introducing Rethink Priorities’ Cross-Cause Prioritization Series by @Marcus_A_Davis, and there has been no reply so far.

Hi Nick. Do you know about any public explanations of why indirect effects on macroarthropods like soil ants and termites are not included? I suspect you have in mind the comments below. However, they apply to plants, microorganisms, nematodes, and microarthropods, not to macroarthropods like soil ants and termites. 

Laura Duffy said on 17 July 2025:

We didn’t do the welfare range calculations for plants, protists, nematodes, etc, because we don’t think the methodology is appropriate for organisms that lack a complex brain and/or nervous system

Bob Fischer said on 28 July 2025:

1. It's true that we don't think you can take our methodology and extend it arbitrarily. We grant that it’s very difficult to draw a precise boundary. However, it's standard to develop a model for a purpose and be wary about its application in a novel context. Very roughly, we take those novel contexts to be ones where the probability of sentience is extremely low. We acknowledge that we don’t have a precise cutoff for “extremely low,” as establishing such a cutoff would be a difficult research project in its own right. There are unavoidable judgment calls in this work.

[...]

3. We don't think that the assumptions of our "mainline welfare ranges" imply anything about the welfare ranges of plants, nematodes, and microorganisms, as the models simply aren't intended to be used the way you are using them. That's why we aren’t replying to you about the welfare ranges of plants, nematodes, and microorganisms. We would need to do an independent project to form opinions on your questions. Right now, we don’t have the funding for that project.

Bob said on 21 November 2025:

On the macro-level issue of priorities, I've gathered some of my thoughts here.

From the doc linked above:

Second, I want to do good, not just good in expectation. So, as the probability of sentience drops, I become more wary. Insects are fairly close to my limit. Right now, we have some evidence for sentience in some insect orders, which I find reasonably compelling. However, it isn’t compelling primarily because it checks some number of boxes in Birch’s precautionary framework; instead, it’s compelling because of its breadth and richness. We have nothing like the evidence for sentience in Drosophila [small fruit fly] for mites, springtails, thrips, and the like. For that reason, we can respond to the stock objections to sentience in insects. We can’t do anything analogous for these smaller arthropods. (And recall that their brains are one or two orders of magnitude smaller than the brains of many insects. I doubt there’s a linear relationship between sentience and any such neurophysiological feature; at some point, I’m inclined to think that the probability falls off a cliff.)

As I commented above, I estimate the effects of chicken welfare campaigns on ants and termites are much larger than those on chickens for the sentience-adjusted welfare ranges presented in Bob's book. For this not to hold, I think the sentience-adjusted welfare ranges of ants and termites would have to be much lower than that of black soldier flies (BSFs). I would be surprised if this was the case under the methodology of Bob's book. Godfrey et al. (2021) estimated 90 k neurons for a desert ant, and 92.5 k for a fruit fly (“vinegar fly”), and “individual number of neurons”^0.188 explains pretty well the welfare ranges in Bob’s book, as illustrated below.

Thanks, Ryan. Buck and Ryan, do you see any bet I could make with any of you against short transformative AI (TAI) timelines, or what they supposedly imply, that is beneficial for both of us?

Have you considered accounting for effects on soil invertebrates? One of the "key takeaways" from your work on risk aversion was that "Spending on corporate cage-free campaigns for egg-laying hens is robustly[8] cost-effective under nearly all reasonable types and levels of risk aversion considered here". However, I suspect the vast majority of interventions perform worse than inaction accounting for effects on soil invertebrates under moderate levels of any type of risk aversion you considered (“avoiding the worst” risk aversion, difference-making risk aversion, and ambiguity aversion). I estimate cage-free campaigns for laying hens change the welfare of soil ants and termites much more than they increase the welfare of chickens for the sentience-adjusted welfare ranges presented in Bob Fischer's book about comparing welfare across species. I have little idea about whether those campaigns increase or decrease the welfare of soil ants and termites. So I do not know whether they increase or decrease animal welfare.

Of course, inaction is not the solution. I would like to see more research on comparing welfare across species. I can easily see effects on soil ants and termites being negligible, although I believe this would also imply a very low cost-effectiveness for interventions targeting invertebrates (like electrically stunning shrimps). In addition, I would prioritise building capacity to help soil invertebrates. They may well matter.

we aim to include more topics (which could include “meta” work and research) in future iterations of the model

Good to know.

Hi Nick. I agree it is important that the questions are easy to answer. However, I would say there are simple ways of letting users express their uncertainty. For the question about how much animal welfare should factor into funding decisions, there could be an option saying something like "I am very uncertain about which of the 4 views above I should pick", or users could be allowed to give weights to each of the 4 views (instead of giving a weight of 1 to a single view). Then these answers could be used to define distributions for the probability of sentience, and welfare range conditional on sentience. Wider distributions would tend to result in a higher expected value of perfect information.

Thanks for the links, Laura. To clarify, I meant to ask whether you have considered making recommendations that specifically target decreasing the key uncertainties that matter for cross-cause prioritisation. For example, decreasing uncertainty about welfare comparisons across species by supporting work like RP's moral weight project.