Unfortunately I think this post is otherwise not very relevant, mainly because no one uses Contrapest [...]
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Since Iām not sure Evolve works either, it may be that any fertility control product used in the future has an entirely different formulation, making speculation here quite difficult.
Do you agree replacing the rodenticide bait with ContraPest may impact soil animals much more than rodents for my estimate that it decreases cropland by 0.413 m2-year per initial rodent? If so, how much smaller do you think the change in cropland would have to be for replacing the rodenticide bait with Evolve to robustly increase animal welfare (in expectation, and accounting for all animals)?
Here is an illustration of how to quickly estimate the effects on soil animals for other fertility control baits. Imagine replacing the rodenticide bait with Evolve increases or decreases cropland by 10 %. I estimate full depopulation with the rodenticide bait increases cropland by 0.481 m2-year per initial rodent. So replacing the rodenticide bait with Evolve would increase or decrease cropland by 0.0481 m2-year per initial rodent (= 0.10*0.481). This means the effects on soil animals would be 11.6 % (= 0.0481/ā0.413) as large as for replacing the rodenticide bait with ContraPest. For effects on soil animals 10 % as large (a round fraction to simplify the calculations), depending on the biome replacing the cropland, my estimates for the change in the living time of soil animals per initial rodent for full depopulation with fertility control instead of rodenticide bait would range from:
1.52 to 43.7 soil-ant-years.
9.46 to 68.5 soil-termite-years.
65.1 to 3.00 k soil-springtail-years.
134 to 5.07 k soil-mite-years.
466 to 8.01 k soil-arthropod-years.
To clarify, the reason I viewed (at time of writing of the previous post) that rodenticide replacement on islands might be approximately ecologically inert is that conservationists use products until rats are entirely eradicated and then stop. [...]
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I strongly doubt that comparing ācost [cropland] to prevent one birth/ācause one deathā is the right comparison. The population dynamics of suppressing fertility are different than those from killing adults, so the timeline to eradication (in the island context) and the application volumes would likely be different, among other things.
Lorenzo Buonannoās comment made me update the post in agreement with the 1st paragraph above, although I only read this paragraph after my update. I am now using the amount of rodenticide and fertility control bait for full depopulation per initial rodent instead of the amount needed to kill one rodent, and prevent one rodent birth.
[...] You have this short duration of time during the eradication, and then a long period after where conditions on the island are basically the same. [...]
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If weāre talking about use in settings other than islands, I want to reiterate that those are definitely not ecologically inert even to some approximation, and there are tons of things youād have to look at besides production method if you wanted to estimate total animal effects. Age structure changes in rat populations, food web dynamics, most rodent fertility control agents appear to have reasonably strong insecticidal effects while brodifacoum doesnāt affect most invertebrates weāve studied, etc.
I neglect differences in the population of rodents between the 2 depopulation methods for simplicity, and underestimating the effects on soil animals.
although I do wonder if the limited duration of these eradications and amount of use for island conservation relative to overall production is high enough to make a meaningful impact on land use? I donāt think these things are continuous so a small enough demand shift signal might not have any impact? Just speculating...
I agree cropland changes in steps, but I do not think this changes the overall picture. Relatedly, it may naively seem that decreasing the consumption of chicken by 0.1 kg does not change the production of chicken if this can only be adjusted by multiples of e.g. 1 k kg. However, in this case, a better model would be that decreasing the consumption of chicken by 0.1 kg would increase by roughly 0.01 pp (= 0.1/ā(1*10^3)) the probability of the production of chicken decreasing by 1 k kg. So the expected reduction in the production of chicken would still be roughly 0.1 kg (= 1*10^-4*1*10^3).
The dosages are difficult to determine. [...]
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Other complications: The dosing requirements also seem to be quite different between species of rats. [...]
Accounting for considerations like these would increase uncertainty. However, the final conclusion would still be that controlling the fertility of rodents instead of killing them can easily increase or decrease welfare, even on islands?
I think Iām just generally more comfortable than you balancing my uncertainties with a combination of direct work on arthropods, and work on things that have (1) high non-arthropod upsides and (2) where Iām clueless about the effects on arthropods. [...]
Thanks for the comment, Mal.
Do you agree replacing the rodenticide bait with ContraPest may impact soil animals much more than rodents for my estimate that it decreases cropland by 0.413 m2-year per initial rodent? If so, how much smaller do you think the change in cropland would have to be for replacing the rodenticide bait with Evolve to robustly increase animal welfare (in expectation, and accounting for all animals)?
Here is an illustration of how to quickly estimate the effects on soil animals for other fertility control baits. Imagine replacing the rodenticide bait with Evolve increases or decreases cropland by 10 %. I estimate full depopulation with the rodenticide bait increases cropland by 0.481 m2-year per initial rodent. So replacing the rodenticide bait with Evolve would increase or decrease cropland by 0.0481 m2-year per initial rodent (= 0.10*0.481). This means the effects on soil animals would be 11.6 % (= 0.0481/ā0.413) as large as for replacing the rodenticide bait with ContraPest. For effects on soil animals 10 % as large (a round fraction to simplify the calculations), depending on the biome replacing the cropland, my estimates for the change in the living time of soil animals per initial rodent for full depopulation with fertility control instead of rodenticide bait would range from:
1.52 to 43.7 soil-ant-years.
9.46 to 68.5 soil-termite-years.
65.1 to 3.00 k soil-springtail-years.
134 to 5.07 k soil-mite-years.
466 to 8.01 k soil-arthropod-years.
Lorenzo Buonannoās comment made me update the post in agreement with the 1st paragraph above, although I only read this paragraph after my update. I am now using the amount of rodenticide and fertility control bait for full depopulation per initial rodent instead of the amount needed to kill one rodent, and prevent one rodent birth.
I neglect differences in the population of rodents between the 2 depopulation methods for simplicity, and underestimating the effects on soil animals.
I agree cropland changes in steps, but I do not think this changes the overall picture. Relatedly, it may naively seem that decreasing the consumption of chicken by 0.1 kg does not change the production of chicken if this can only be adjusted by multiples of e.g. 1 k kg. However, in this case, a better model would be that decreasing the consumption of chicken by 0.1 kg would increase by roughly 0.01 pp (= 0.1/ā(1*10^3)) the probability of the production of chicken decreasing by 1 k kg. So the expected reduction in the production of chicken would still be roughly 0.1 kg (= 1*10^-4*1*10^3).
Accounting for considerations like these would increase uncertainty. However, the final conclusion would still be that controlling the fertility of rodents instead of killing them can easily increase or decrease welfare, even on islands?
I agree.