All species have an inherent right to exist, insist the 8,000 scientists from the International Union for Conservation of Nature who have just compiled a list of the world’s 100 most endangered species. Since all the life-forms listed are unique and irreplaceable, they argue, there is an ethical imperative which places on society an obligation to save them.

But is this so? Many certainly feel that way, particularly when the animal concerned is cute or cuddly. And there is a clear logic to ensuring the survival of those species which are of demonstrable use to humankind. But where does that leave the three-toed pygmy sloth, of which only 500 remain on an island off the coast of Panama?

Without doubt, we are not sentimental about the eradication of some species – the smallpox virus, for example, or the mosquito which carries the deadly malaria micro-organism. Not only would too absolutist a position protect them. According to some, such as Dr Sarah Chan of the Institute for Science, Ethics and Innovation at Manchester University, it would even place upon us an obligation, when it is technically possible, to resurrect long-gone species like the dinosaur.

That said, extinction is a natural phenomenon not an ethical one, and there is a difference between natural extinctions and those driven by the behaviour of humans. All the mammals, plants and fungi on the endangered 100 list are at risk because their habitats are appropriated for human use. A clearer case can hardly be made for our moral obligation to preserve for future generations the species we inherited.

There are also good grounds to question a utilitarian “what’s in it for us?” approach. Nature is more than a commodity to be valued and placed in the marketplace for its disposal to the highest bidder. In any case, such is the character of scientific discovery that we cannot afford to be dismissive of the willow blister fungus, which grows only on trees in Pembrokeshire, whose habitat is being squeezed. It may well have a use of which we as yet are ignorant. If it becomes extinct we will never know.