There is not enough consideration of non-human animals in the longtermist debate. This essay argues that when animals are properly included in longtermist calculations, depopulation emerges as the most morally defensible path under a utilitarian framework. I agree with Mogensen when he says that humans must have humility when considering this debate and thus take into considerations the effects of humanity’s existence on other species. I assume for the purpose of argument that animals have enough sentience for their lives to be considered in this debate. This essay adopts a broadly utilitarian framework, holding that the moral value of future outcomes depend on the balance of pleasure and suffering they contain. I begin by arguing that the argument for neutrality is the strongest argument and that negative utilitarianism is too negative of a framework. Then, I argue the case for depopulation and why it is important to consider animals in the debate, concluding that a moderate stable low population provides the most beneficial outcome for humans and animals. This essay critiques Longtermism rather than is completely against it as a concept. 

The neutrality argument used by Steele in Chapter 5 to defend longtermist views, that future worthwhile lives are inherently neutral, is an argument I will use to critique Longtermism. The possible existence of extra human lives don’t automatically make the world a better place on their own, instead we should focus on current lives and the fate of people who will be worse off. This argument is convincing because it is not overly optimistic: It does not lose sight of the fact that a lot of the lives in the future may not bring about positive welfare and instead cause suffering to other people or animals. Steele uses welfare and quality of future lives to argue that the longtermist debate should not be about maximizing future humans, but instead maximizing future welfare. Therefore, in maximizing this welfare we must take into account the welfare of future animals. This argument supports the conclusion that a smaller, happier population could be better than a larger one with mixed welfare, reframing the longtermist argument to prioritize the well-being of existing and certain future beings. The argument of neutrality, if correct, would mean that there is no moral reason to create more humans, instead stabilizing the population may increase the average welfare and reduce harm to animals.

Negative utilitarianism as a concept would argue that there is more pain than pleasure in the continued existence of humans, due to our suffering as well as the suffering we inflict on non-human animals. This theory focuses on minimizing suffering so it would argue the case that the most moral solution is human extinction. But, it prioritises reducing suffering so much that it justifies extinction, this overlooks the positive value of flourishing. Depopulation avoids this outcome by preventing catastrophic suffering without ending human value.

If neutrality is correct, then we have no moral obligation to create additional humans, instead reducing population pressure may increase total welfare by mitigating suffering, particularly for non-human animals. Longtermist make the assumption that more humans means more value, but this is rejected by neutrality. Depopulation may actually reduce existential and moral risks, as presented in Chapter 21. For example, fewer humans would mean less factory farming which would reduce the suffering of the animals. Additionally, less humans would slow down climate change, reduce the risk of pandemics and put less pressure on animals habitats. Considering these arguments it seems persuasive to consider that depopulation may be the best outcome, especially when bringing the welfare of animals into view. The argument for depopulation does not mean extinction, just stability at sustainable levels.

Although with less humans there may be less innovation, this would be outweighed by the welfare gains for humans as well as animals. The trade-off of prioritizing the existential risks of overpopulation rather than the civilization resilience brought about by more humans makes sense because risks from overpopulation are a greater concern. Additionally, arguing that depopulation would weaken civilization resilience due to it reducing innovation and economic productivity assumes that human continuity depends on constant growth, which is empirically and morally questionable. A smaller but technologically stable population could maintain the essential knowledge to mitigate existential risks while dramatically lowering ecological pressures. Therefore, depopulation solves the risks to humanity and does not pose problems to humanity’s long-term security, but instead may increase it. 

Once we move beyond a purely anthropocentric framework, the moral stakes of population ethics expand exponentially. Including non-human animals in longtermist calculations radically alters the outcome, since the scale of their potential welfare vastly exceeds that of humans, this is detailed in Chapter 25. Longtermism neglects non-human animals almost entirely, with MacAskill’s book only having one subsection of a chapter on animals. This is axiologically incomplete because there are over 100,000 vertebrates for every human; vertebrates being the animals that we can reliably assert are sentient. Even if we assume that animals have less possible maximum welfare than humans, the total possible welfare of future animals will be several orders of magnitude higher than the possible maximum welfare of all future humans. Due to the number of animals to exist in the future, we must work to improve the quality of life for these animals so they will have the highest positive welfare. Even though many animals’ lives involve suffering, such as vulnerability to predation or scarcity of food and water, their net welfare still exceeds humans due to the vast number of animals, so animal welfare interventions can vastly change long-term outcomes. Depopulation will greatly help with this due to less factory farming and more habitat restoration. Therefore, when considering animals, depopulation seems like the condition where the most positive welfare is created.

This argument exemplifies what Mogensen calls “longtermist humility”: recognising that human welfare is not the only or even primary determinant of moral value in the distant future. A genuinely impartial utilitarianism must weigh all sentient welfare equally, which may lead us to prioritise ecological balance and population restraint over expansion.

To conclude, when non-humans animals are included in the considerations of the Longtermist debate the calculations for future welfare are fundamentally changed. The argument for neutrality implies that there is no welfare lost and therefore it is morally sound to have fewer humans through controlled, steady depopulation. The effect that humans have on animals’ welfare also supports the conclusion of depopulation. By properly prioritising welfare, rather than sheer population growth, as Longtermism should, it is clear that the best solution is not simply the most humans possible. Therefore, a sustainable, low population future, guided by longtermist humility and inclusive utilitarianism, offers the most ethical vision for both human and non-human animal flourishing.