I have talked about why I believe that veganism is a an ethical position aligned with everyday ethical views about how we treat others. I have also explained how on these grounds we can evaluate which kinds of food production are most ethical. I concluded that we are almost always better to farm only crops than to farm crops AND other animals.

Nonetheless, pest control in cropping remains a significant concern. Given that we very likely cause substantial suffering and death to invertebrate species in particular and that pest management practices are threatening many species with extinction, I think we have to give further thought to how the decision to grow only crops can withstand scrutiny.

The basis for offering moral consideration to other species really rests on sentience. It can only be the case that we have that kind of ethical duty to other species when we can be reasonably confident that they experience the world from a first-person perspective. That is, there is something it is like to be them. Perhaps we might even restrict our concern to those species that can feel pain.

Today, evidence strongly suggests that many invertebrate species are sentient and some may even feel pain. Given it is possible that quadrillions of insects are killed worldwide each year to grow crops, we seem to be causing considerable harm to pest species such as insects and I have argued that it seems wrong to inflict unnecessary harm and suffering on other species. Where to from here?

One option I will propose is that we take into account certain biological factors. The one I am interested in here is reproductive strategy. Species tend to be either K or r strategists. I know that this idea is less favoured these days as an explanation about survival strategies in species, but as a broad-brush consideration I think it still holds some value. K-strategists are longer lived, have few offspring, care for them longer and invest greater resources in their survival. K-strategists tend to be larger animals. An example is cattle. R-strategists on the other hand are shorter-lived, have many offspring, often invest little effort in raising their offspring and are smaller animals. An example is insects. Rodents are also r-strategists.

Consistent with the natural “intent” inherent in the evolution of these two kinds of reproductive strtagey, I propose that we owe a greater duty to individuals of K-selected species and a lesser duty to individuals of r-selected species. K-strategists tend to experience pain in ways that support behaviour adaptation and learning, leading to greater concern for how the self and any offspring go in the world. R-strategists may not even feel pain in many cases (insects) and often show less concern for individual experiences. As K-strategists hope to achieve species success from individual success, we can see why worrying about each animal as an individual is very important. R-strategists on the other hand achieve species success from an overall maximal reproductive potential – many offspring lead to many survivors, even if many die young (which they do).

At the individual level then, we owe a greater duty to K-strategist individuals than we do to r-strategist individuals. Just the same, in both cases, we owe a collective duty to the species to prevent unnecessary harmful impacts such as extreme thinning of populations and/or extinction. On that view, killing pest insects (and rodents) to protect crops is defensible on practical grounds (we have to grow food to live and insects threaten our success) and on relative ethical grounds of least harm (the experiences of individual insects matter sufficiently less that we can ignore this concern for all practical purposes – we are doing less harm to kill r-strategist individuals than to kill K-strategist individuals).

However, our duty to the species and the environment is such that we cannot be indiscriminate in pest control when the results affect biodiversity, ecosystems and threaten species with extinction. We should encourage improved pest control techniques in order to minimise risks to insect populations and prevent species extinction, but not feel that we have to apologise for killing individual r-strategist pests.