Many conservation measures in environmental biology such as the IUCN red list or measures against invasive species are done on the level of species rather than on the level of individuals. Often, individuals of a invasive species are killed to protect (rare) native species (e.g. ferral cats are killed in Australia). In some way this seems strange to me because in human ethics, we are very much concerned about the rights of individuals. This approach strikes me as natural because only individuals can have positive or negative experiences whereas the construct of species cannot.

As a thought experiment, let's assume that an invasive species A slowly displaces the native species B because species A is more "successful" than species B in this ecological niche. The harm done by species A is in the form that species B is not as successful in reproduction as species A. Conservation biologists are upset about this scenario and decide to kill member of species A to protect species B. But in this way, more harm to individuals is done compared to the scenario where species A just displaces species B. This is because killing is more harmful to individuals than simply not reproducing.


  • How can we defend the killing of individuals of a species A in order to protect the survival of species B (in the thought experiment above)?
  • How can we defend the concept of species in animal rights? For example: What exactly is the moral difference of killing 2 giraffes out of a total population of 1 million versus killing the last 2 giraffes on earth?
  • Can an abstract construct such as a species even have rights of itself, like a right to survive (as a species)?

Thank you.

3 Answers 3


These are some interesting questions.

I'll start with the third one:

Can an abstract construct such as a species even have rights of itself, like a right to survive (as a species)?

Here you're importing a pretty strong assertion in the "abstract construct" language. There's a lot of different ways of parsing what a species is. On the one hand, it's a type. Classically, it was a Form or Essence. We'll skip Plato here, but for Aristotle's idea of an essence. What happens is that we are recognizing something in giraffes when we look at them that makes the giraffes. To simplify that, it's not that we are making up "giraffe", Aristotle thinks it's an empirical observation.

Not everyone agrees, but the modern biological classifications building on Linneaus took species to be real kinds out there in the world. As we've refined that, we've realized he was wrong on some. And we've gotten some blurry realities where two species can intermate or even one's where they have to.

But bringing us back to ethics, I'm going to make a claim: only abstractions have rights at all, because rights are abstraction. Again, what matters is if they are mere abstractions. Abstracting is kind of what humans do and need to do in order to think.

But this question is centrally important to your other questions because it provides the scope of what we are answering. So now we can return to your middle question:

How can we defend the concept of species in animal rights? For example: What exactly is the moral difference of killing 2 giraffes out of a total population of 1 million versus killing the last 2 giraffes on earth?

On a spectrum, if we take species to be merely abstract constructs with no substantive reality behind them, then it's going to be hard to explain why any sort of action towards things based on this arbitrary distinction would matter. On the other hand, if we take them to be abstract constructs with some basis in reality, we could begin to add diversity concerns. If we take them to be real kinds (like Aristotle), we might be able to strengthen that further.

At a minimum to make it matter it cannot be merely arbitrary (or rather if merely arbitrary species matter, then we're just writing pure fiction here and we could make our ethical theory center on dice and wood grain directions). Setting that aside, there are several different but related motives I can imagine using:

  1. Valuation of a specific species [e.g., humans]
  2. Valuation of a specific kind of species [i.e., ones that seem to demonstrate some rationality: e.g., humans, dolphins, monkeys, bears ?]
  3. Valuation of diversity of species
  4. Valuation of biodiversity with species seen as integral to that
  5. Valuation of the planet and a belief biodiversity is important such that we need differing species.

Now the why of the valuation could be anything. It could be a utilitarian calculation. It could be Singer's pain minimization view. It could be religious. It could be spiritual but not religious. It could be Kantian. It could be intuitionalist. It could be purely economic.

Depending on the reasoning, it might be acceptable to kill of the last two hawks to save millions of momonga. Say for instance, if your preference is the cuteness of the animal or its relative intelligence. Alternately, you might consider some species to have prices and others to have worth but not price. (I for instance place the price of mold at about 200 yen).

This moves us to your first question:

How can we defend the killing of individuals of a species A in order to protect the survival of species B (in the thought experiment above)?

It would depend on our reasons for valuing specific species. To give an example of where it might be permissible, consider Peter Singer's view that what we want to do is minimize pain and suffering and that animal pain and suffering are not that different from our own (i.e., they count). If that's the reason we should kill, then it seems we would just need to calculate the net suffering produced by keeping invasive species A around.

Again, for some reason to value animals, it won't matter. If for instance, the invasive species are humans and the existing species are dolphins and you think both are rational, then it's unacceptable to wipe one out to help the other.

  • This was an interesting read. Thank you very much shedding light on this! Nov 9, 2014 at 6:54

I think these arguments fall back on biodiversity as a basis. (I am not a biologist, so this is kind of wooly, and the wording may not be adequately precise.)

Killing off a species, or even a bloodline matters much more than killing of a relatively large number of individuals, because the ability for the system to adapt to future changes comes from preserved inefficient diversity among the individuals in each species. As environments shift more, the need for genetic diversity needed to adapt to unexpected change grows, but competition eliminates 'unprepared' species faster. The likelihood then increases that some major and important aspect of an interdependent system will go unfulfilled, because a single species lacks the diversity to adapt to some change. For the want of some preserved atavism or mutation in a species or narrow range of species, an entire system collapses, and other systems may not be able to extend efficiently into that vacated space.

We eliminate invasive species without predators because they will crowd out indigenous species and reduce the total biodiversity of the system. They are not going to be lost in their native habitat, and they are going to reduce the numbers among species in their new habitat, perhaps so much that important bloodlines or whole species will be lost. So the overall adaptability of whole systems in the larger region will decline.

If the imported species is endangered at home, or if it develops local predators, or if it balances out against the natives on the basis of some kind of niche competition, we would no longer work to eliminate it. Both species are likely to survive in reasonable numbers.

Edit: Relation to Human Ethics

I think that we can relate to this on a human level as well. We are more appalled by genocide or family-execution vendetta than random violence. And at the same time we defend ourselves, and even sometimes other people quite distant from ourselves, against hostile invaders or unnatural competition aimed specifically at specific sub-populations (q.v. World War II...)

We have a focus on individuals that animals do not. But we instinctively see the extra danger and greater evil in destroying whole extended families, or whole differentiated gene pools (which we perceive as races or nations), or in letting invading hordes eliminate whole native populations (except when we happen to be among the invaders).


Some of your questions are answered by my answer (and the answers of others) to this question on extinction.

Since I argue in that answer that extinction is really really bad, it pretty much covers your questions also. In brief (also pretty brief there):

  • Yes, a species can have "rights" (at least the right to not go extinct due to our actions), at least if we accord any rights at all to any non-human animal.

  • Giraffes exist first and foremost to make more giraffes. 999,998 giraffes can make more giraffes--not quite as many as 1,000,000 can, but you likely won't notice the difference in a couple of generations. 0 giraffes cannot make any more giraffes. Even 2 is probably not enough due to genetic bottlenecks, but 0 certainly isn't. So it's not equivalent at all.

  • If A is making B extinct, and it's doing so because we brought A into a place where it can make B go extinct, it may be very appropriate to kill A to try to rectify the problem.

It is true that philosophy tends to focus on individual rights, but I am not entirely sure that this isn't an error. Philosophy hasn't taken very much stock of evolution so far (aside from silly titles of books like "Freedom Evolves"). For instance, if some system of morality might lead to a situation where murder is condoned, it provokes consternation. But people don't typically ask if the system of morality might advocate for the extinction of the human race.

  • Thanks Rex. This (i.e. biodiversity) is the argument I as a biologist would probably value strongest. Nov 9, 2014 at 7:21

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