This somewhat sentimental vocabulary lurches into lurid melodrama when Nussbaum likens animal predation to crimes in the human world: “To say that it is the destiny of antelopes to be torn apart by predators is like saying that it is the destiny of women to be raped.” Such rhetoric strikes me as in tension with what I take to be the utilitarian calculus underlying Nussbaum’s major argument. But other, more rigorous proponents of the moral exigency of the suffering of prey animals lapse into it too. “Viewed from a distance,” McMahan writes in “The Moral Problem of Predation,” which as far as I can discover is the most systematic defense of a strong interventionist position, “the natural world may present a vista of sublime, majestic placidity. Yet beneath the foliage and concealed from the distant eye, a continuous massacre is occurring.” (Darwin said it first, and better: “We behold the face of nature bright with gladness, we often see superabundance of food; we do not see or we forget that the birds which are idly singing round us mostly live on insects or seeds, and are thus constantly destroying life; or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds and beasts of prey …") William MacAskill, famous as a proponent of effective altruism, is even more gothic than Nussbaum and McMahan — in an essay co-written with Amanda MacAskill, he compares lions to human serial killers and suggests that their extirpation is no less justified.
Unlike Nussbaum, who tends to emphasize human sadism, McMahan focuses on human pity toward prey species: “There is some intuitive support for the idea that there is a moral reason to intervene against predation. If one were to happen upon a young animal that was about to be captured and slowly devoured alive, piece by piece, by a predator, one’s impulse would be to frighten off the predator, if possible.” And he is much less circumspect than Nussbaum about the moral duty to intervene in nature to eliminate predation and thereby reduce the sum total of suffering. On this topic, he permits himself flights of utopian (or dystopian) science-fictional fancy:
There are two ways in which the incidence of predation could be significantly reduced, perhaps eventually to none. One is to bring about the gradual extinction of some or all predatory species, preferably through sterilization, and with the exception of the human species, which is capable of voluntarily ending its predatory behavior. The other, which is not yet technically possible, is to introduce germ-line (that is, heritable) genetic modifications into existing carnivorous species so that their progeny would gradually evolve into herbivores, in fulfillment of Isaiah’s prophecy.
McMahan acknowledges that, given present limitations to both genetic intervention and our knowledge of ecological systems, this brave new world is not yet feasible. But he sees reason for hope; after all, science often advances much faster than expected, and in unpredictable ways: “What may now seem forever impossible may yield to the advance of science in a surprisingly short time — as happened when Rutherford, the first scientist to split the atom, announced in 1933 that anyone who claimed that atomic fission could be a source of power was talking ‘moonshine.’” (I am not sure the example proves just what he wants it to.)
Naturalists are so far immune to these arguments; in fact, the reintroduction of predator species to areas where humans had driven them out is a priority of many ecologists. Daniel Blumstein, an ecologist and evolutionary biologist at the University of California at Los Angeles who studies predator-prey dynamics, told me that although he considers it important to minimize animal predation when it is caused by human activity — for instance, when domestic cats decimate bird populations — he doesn’t think “natural predation justifies interventions to eliminate predation in nature.” As McMahan himself acknowledges, the moral intuition of almost all regular people strongly rejects the sort of intervention he advocates. For now, the heaven of the animals is a philosopher’s dream.
Read Martha Nussbaum’s “A Peopled Wilderness” and Jeff McMahan’s “The Moral Problem of Predation.”