In Just Fodder, Milburn investigates the ethics, and politics, of feeding nonhuman animals. Following Palmer (2010), he agrees that, though all animals have negative rights that we have a duty not to violate, we only gain positive obligations towards animals in the contexts of our relationships with them. More specifically, we gain positive obligations towards others when we are morally responsible for making them vulnerable to, or dependent on us in some way. By choosing to bring a companion animal into your home you create a relationship of dependency between her and you. This is because you have closed off any other options that she might have had to take care of herself. She cannot find food for herself, for example, so she depends on you to provide it for her. In Palmer’s (p.91–92) terminology these are external dependencies. Furthermore, domesticated animals have been bred to have certain internal dependencies – after generations of selective breeding they are simply no longer capable of living independently in the wild. Although the individual who adopts a puppy isn’t directly responsible for breeding her, by adopting or purchasing the dependent animal he takes on responsibility for her. The important point here is that it is not simply the interest the companion animal has in being fed that grounds a duty in the owner to feed her. If an interest in being fed were sufficient to ground a duty to feed, then, Milburn argues, humans would also have duties to feed starving wild animals, whose interest in being fed is no less than that of domesticated animals (p.51). Rather it is the relationship between the dependent animal and the particular human being who has created the relationship of dependency that grounds her right to be fed by that human (52–53).

Palmer is primarily concerned with the moral obligations that arise though our individual relationships with animals. While she discusses the possibility that humans might have positive obligations towards domesticated animals generally, these obligations are grounded on either the benefits that individuals might incidentally gain from the general practice of animal use, or on their contribution to the social attitudes that maintain such institutions (106–113). Milburn explicitly argues that our normatively significant relationships can also be collective, political ones, grounded on our membership of morally significant groups such as states, or, perhaps, the human species. This is important, as it allows Milburn to maintain that even domesticated animals without any particular guardian have a right to be fed and protected. This is because domesticated animals, as a group, are dependent on human beings collectively. Human beings brought companion animals into their community by domesticating them, and bred them selectively to have certain features. Companions (and other domesticated animals, presumably) generally have both internal and external vulnerabilities to human communities or “the human community”, and humans collectively have “the lion’s share of responsibility for this” (p.72). Milburn draws an analogy between the individual responsibility created by an individual human deciding to bring an animal into his home, and the collective responsibility generated by humans as a whole “bringing a whole population into our society and cutting off alternative possible futures for all of its individual members” (p.72). This collective moral responsibility for the general relationship of vulnerability and dependency between domesticated animals and human beings justifies differential treatment of domesticated animals and free-living ones. A starving domesticated animal is the victim of an injustice if humans fail to help her, because humans collectively are responsible for her dependency and thus for her current plight. No such relationship, Milburn claims, exists between humans and free-living animals. Humans have not created any internal or external dependencies in free-living animals, nor are we usually responsible for their plight. So while we have strict negative duties not to harm free-living animals, we have no positive duties towards them (p.73).

In the following comments I will assume that the relational account is correct, and that positive duties only emerge in the context of certain morally charged relationships. I will also accept, as Milburn seems to, that it makes sense to say that humanity as whole can have collective responsibilities toward animals because of the actions of our ancestors. I will argue however that if his account of collective responsibility for historic wrongdoing is correct then we have a greater degree of moral entanglement with wild animals than is generally assumed, and that these entanglements plausibly generate collective obligations to assist them. The upshot is that even relational accounts of positive obligations may entail that we have significant duties towards wild animals. Furthermore, those who argue that we have reasons of beneficence to intervene in nature to help animals could bolster their arguments by arguing that we also have collective duties to rectify the wrongs we have historically done to animals.Footnote 1

The Anthropocene Challenge

Milburn argues that humans generally aren’t entangled with wild animals in the way that we are with domesticated animals. In short, since we haven’t created a relationship of dependency or vulnerability with them, and since we aren’t responsible for their plight, then we don’t have any duties of justice to help them. Though life for wild animals is hard, and there is much we could do to help them, we aren’t obligated to do so. He acknowledges however that the claim that we have had little or no impact on the lives of wild animals is open to challenge. It has been proposed that we are currently living in the ‘Anthropocene’, a distinct geological epoch in which human influence on the natural world is “both pervasive and defining” (p.172). If our impact on the natural world is sufficiently pervasive, then we can no longer assume that we are not entangled with the lives of wild animals in morally relevant ways. If we have created vulnerabilities in wild animals, and if we are responsible for some of the apparently natural harms which they endure, then it may be that we owe them positive duties of assistance, just as we do domesticated animals. He uses climate change as a salient example. It is clear that humans are both morally and causally responsible for climate change. If it is the case that the changes to the planet are having negative effects on wild animals, then we can no longer claim that we have no duties to help them.Footnote 2

Climate change poses severe challenges to wild animals, and our collective responsibility for it certainly entangles us in their lives in morally relevant ways. At the very least, it gives us a duty to help animals to adapt to the changing climate, and perhaps to feed those animals who are no longer capable of feeding themselves because of it. Our duties in this regard though are limited to mitigating or rectifying the negative effects that anthropogenic climate change has on wild animals. So, though we may have duties to assist some wild animals, such as those niche specialists who cannot effectively adapt to climate change on their own, we have no general duty to help wild animals who suffer from harms unrelated to climate change.

Climate change is far from being the only impact that humans have had on the lives of wild animals, however. Below I will suggest some other ways in which pervasive human effects on the planet have made us collectively responsible for the plight of wild animals. These involve significant changes to the landscape and to the species composition of various ecosystems that human beings have caused from prehistoric times up to the present day. One might object that it is implausible that human beings today bear any responsibility for the actions of their ancestors thousands, or even tens of thousands of years ago. I agree that this is counterintuitive. There seems to be little connection between us and our distant ancestors, and it sounds harsh that we would inherit the guilt for actions they performed. However, if Milburn’s arguments about our collective duties to companion animals depend on our ancestors having domesticated them, then it should follow that we also bear responsibility for these other harms caused to wild animals by our ancestors. That is, if modern humans somehow bear collective moral responsibility for the domestication of animals thousands of years ago, then it’s not obvious how we could avoid the conclusion that we also bear some responsibility for the various harms that our ancestors inflicted on wild animals.

Extinction of Large Herbivores

As prehistoric humans spread across the globe, a trail of extinctions of large animals followed them. The ‘overkill’ hypothesis suggested that as humans arrived in each new part of the world, the extinction of that area’s megafauna quickly followed, as humans either hunted them to extinction, or outcompeted them (Martin 1967). A 2022 study from Tel Aviv suggests that humans have always preferred to hunt the largest animal available to them in any given environment, as it gave the greatest yield of food per unit of effort. When the largest animal was hunted to extinction, humans moved onto the next largest, and so on (Dembitzer et al. 2022). Though it has not been decisively proven, the evidence points towards human responsibility for these extinctions. This wave of extinctions not only caused suffering to the animals our ancestors killed, but it also changed the nature of those ecosystems in several ways. First, large herbivores like woolly mammoths, mastodons, and giant ground sloths contributed to maintaining open landscapes, by feeding on sprouting trees and shrubs. Once they went extinct, this open land became forested (Bakker et al. 2015). Secondly, it is plausible that the extinction of these large herbivores meant that there was more plant material available to be eaten by smaller animals, and so their numbers likely increased.

It is plausible that both these changes had an enduring negative impact on the welfare levels of wild animals. First, if one believes that there is net suffering in nature, then, all else being equal, one should prefer ecosystems with lower levels of primary productivity, as this ultimately results in fewer animals, and less suffering. Tomasik (2022) has argued that forests generally have higher primary productivity than open habitats such as grasslands. If this is correct, then the newly forested areas may have had more animal life and hence more suffering than the open habitats maintained by the large herbivores.

Second, philosophers researching welfare biology have speculated about what kinds of ecosystems are more conducive to positive wellbeing for wild animals. Looking at modern day ecosystems, Faria and Horta (2019), Tomasik (2022), and Hecht (2020) have all argued that, all else being equal, when it comes to wild animal welfare, we should favour ecosystems with large herbivores like elephants over ecosystems without them. The main reason for this is that large herbivores consume huge amounts of plant matter, reducing the amount available to other animals. This prevents the presence of large numbers of small animals who reproduce in vast numbers. Large herbivores, like modern elephants or the extinct woolly mammoth, plausibly have generally good lives. They have few offspring in whom they invest a great deal of parental care, unlike smaller animals which are generally r-strategists with very high infant mortality rates.Footnote 3 They are also generally relatively long-lived, and are safer from predators than smaller animals. As Hecht puts it, “[t]he concentration of biomass into high-welfare individuals is the ideal function of food chains in wild animal welfare” (Hecht 2020). The extinction of so many large herbivores around the world may have allowed more numerous small r-selecting animals to take their places instead. Since these smaller animals generally have much lower levels of welfare, it is possible that by eliminating large herbivores in many ecosystems across the world, human beings may have inadvertently helped create persistent ecosystems with much more animal suffering than the ones they replaced. If we have replaced higher-welfare ecosystems with lower-welfare ones, then this is a clear way in which we have made ourselves responsible for some of the harms endured by animals. In human terms, it is as if we have eliminated safe neighbourhoods in which inhabitants generally live good lives, and replaced them with more dangerous and unpleasant neighbourhoods in which people’s lives are generally less good.

It might be objected that this is all highly speculative. The case for human-caused extinction of megafauna is still controversial, and even if it were proven it is also not certain whether ecosystems with large herbivores are generally more conducive to positive animal welfare than ecosystems without them. I certainly agree that this is highly speculative. However it seems plausible enough that it is worth taking seriously. It may be the case that future research into welfare biology will decisively prove that ecosystems with large herbivores do contribute to higher welfare, and if this is the case then a ‘backward looking’ welfare biologist might conclude that the actions of prehistoric humans did indeed have a long-lasting negative effect on the welfare levels of wild animals. In any case, if we are unsure about what effects we have had on animals, and hence are uncertain about our current obligations towards them, it seems fair that we should err on the side of taking too much, rather than too little, responsibility for our actions.

Introduction of Species

As humans spread across the planet, they often brought stocks of domesticated animals and plants with them, and this has changed the species composition of those ecosystems significantly. A particularly extreme case is Australia. Dingoes are considered a native species, but they were introduced to Australia by humans around 8,500 years ago. They are the largest extant terrestrial predator on the continent, and there are between 10 and 50 thousand of them across Australia. Subsequently humans have also introduced red foxes (current population around 7 million), cats (of which there are around 2.8 million feral individuals), European rabbits (of which there are around 200 million), and cane toads (between 200 million and 1.5 billion). Given the vast numbers of these introduced animals, which often outnumber ‘native’ animals many times over, in what sense can we really say that Australian wilderness is something natural, rather than the outcome of human choices? It may not be the case that we have created a dependency relationship in these animals, at least in the sense of internal dependency. But it is very clear that these animals wouldn’t be there had we not deliberately chosen to bring them to the continent, and so we may well be morally responsible for many of their external dependencies.

First, by introducing rabbits to the continent, we created a new vulnerability in the native animals. European rabbits were introduced to the continent in 1859, when Thomas Austin had 13 wild rabbits sent to him. In only 50 years rabbits had spread across the entire continent, and today there are estimated to be 200 million of them. Rabbits are extremely adaptive and breed in very large numbers. This has allowed them to outcompete native animals, who found themselves unable to find sufficient food, with some species going extinct. It is clear that humans are responsible for the plight of these animals. However we have also created vulnerability in the rabbits themselves, as they are preyed upon by the dingoes and red foxes, which we also introduced. Our introduction of cats to the continent has also been a disaster for the native animals – it has been estimated that feral cats kill 1.5 billion native animals in Australia each year. Milburn accepts that humans can become responsible for the predatory actions of animals. For example, by rehabilitating and releasing injured predators we thereby become causally and morally responsible for the killings they go on to perform (p.155).Footnote 4 If humans can be individually responsible for predatory killings, then it seems that by collectively introducing predators to new habitats we must also become collectively responsible for those killings, and so we may have duties, grounded in the negative rights of prey animals, to protect them from the actions of the predators we have introduced.

The case of introducing the dingo to Australia also illustrates something important about the moral relationship we have towards wild animals whose lives we have impacted. That is, it needn’t be the case that our actions make things worse for wild animals in general for us to bear moral responsibility for the harms that they endure. Before the dingo outcompeted it (and humans helped kill it off), the thylacine was the apex terrestrial predator in Australia. It undoubtedly inflicted a great deal of death and suffering on the native animals of the continent before humans ever set foot there. If human beings had never set foot in Australia, then it seems likely that the thylacine would still be terrorizing its prey today. Humanity however would bear no obligations of justice to protect prey animals from the thylacine, as we would not have been morally or causally responsible for the vulnerability of these animals. By replacing the thylacine with predators we introduced, and indeed by introducing many of the prey animals that these predators prey on, we have entangled our lives with the lives of these ‘wild’ animals in such a way that we take on duties of justice to protect them.

Finally, though the Australian case is a particularly egregious example of humanity introducing new species, it is far from being an anomaly. Humans have introduced new species all over the world.Footnote 5 Harms caused by introduced species include predation, the spread of disease, and the outcompeting of native animals.Footnote 6 If we thereby take on positive obligations towards and regarding these introduced species, then it seems that we are much more entangled with the natural world, and with the lives of animals, than we ordinarily think.

Land Use

Wild animals obviously depend on having viable habitats to survive. Since the agricultural revolution, humanity has changed the landscape of the Earth almost beyond recognition. This is primarily due to deforestation for farmland. Of the Earth’s habitable land (land that isn’t covered by glaciers, deserts, exposed rock, or beaches) approximately 50% is used for agriculture, and about 37% is forested. This means that many animals have been robbed of the kind of habitat that they need to survive. If we think that animals have a right to their habitats, then this constitutes a rights violation on a massive scale.Footnote 7 Having essentially stolen land from the ancestors of modern-day animals, it may be reasonable to think that we have some kind of duty to pay them reparations. It would be difficult to repay wild animals by simply rewilding more land for them to live on. First, that might violate the rights of human beings who now depend on that land. Second, by rewilding we might become responsible for the harms endured by animals on that land, as we would be deliberately introducing animals to lands on which they would predictably come to harm, either from starvation or from predation. But if we cannot rectify these rights violations by rewilding land, what can we do? I propose that the best currency with which to rectify the harms done to animals by driving them from their land is to try to increase the welfare of wild animals suffering from various naturogenic harms.Footnote 8

Furthermore, it is not just the fact that humans have collectively laid claim to most of the land surface of the planet that entangles us with wild animals. Human infrastructure, such as roads, railway lines, shipping lanes, buildings, and so on significantly impact the lives of wild animals, often in fatal ways. It has been estimated that in the UK over 300,000 hedgehogs die on the roads each year, and a 2023 study demonstrates that road mortality is a significant factor in reducing mammalian populations globally.Footnote 9 Our infrastructure also contributes to habitat fragmentation, by dividing up large natural areas smaller, fragmentary habitats, separated by roads and other kinds of infrastructure. This has significant effects on animal behaviour, including on foraging and mating behaviours, sometimes also resulting in greater predator–prey overlap when prey animals are less able to avoid their predators.Footnote 10


Milburn argues that the domestication of animals by our distant ancestors is sufficient to ground collective positive duties towards domesticated animals for modern humans. However, we have no relationship with wild animals, and so we generally have only negative duties towards them. I have argued that human beings have been entangled with the lives of wild animals for thousands of years. By driving some species to extinction and introducing other species into new lands, and by claiming and transforming most of the planet’s habitable land, we have had long-lasting and pervasive effects on the lives of wild animals. These impacts on wild animal lives are sufficient to ground positive obligations towards them. While this may not be sufficient to show that we have general duties to feed and protect all wild animals from harm, it does suggest that we may have many more positive obligations to wild animals than we think. Even if Milburn is correct that in the absence of relationships with them our only obligation to wild animals is to leave them alone, the fact is that we have not, do not, and arguably cannot leave them alone. We have created vulnerability in wild animals and are in many cases either directly or indirectly responsible for the harms that they endure, and as such we may well have positive duties to rectify those harms, and perhaps to feed and protect those animals whom we have made more vulnerable or dependent than they would have been in the absence of our actions. The wild, like our companion animals, may have become ‘inextricably tainted with human agency’ (p.73). Even on a purely relational account of animal rights then, it seems possible to support a program of large-scale intervention in the natural world.