Just as I suspect that multiculturalists have a lot of different restaurants and cuisines in mind when they praise multiculturalism, so I suspect that most of those who espouse biodiversity as a good in itself are thinking mainly of attractive or at least of harmless creatures, rather than, say, Ascaris lumbricoides, the giant (and repellent) roundworm that infects children and can cause intestinal obstruction, or Dracunculus medinensis, the Guinea-worm that, once it emerges from the skin of the foot, must be wrapped round a stick and pulled out slowly and painfully over weeks or months. It is not difficult, in fact, to think of many species that would not much be missed.
The espousal of biodiversity as a good in itself, then, is a form of pagan theodicy, in which Nature is ultimately benevolent and knows best, appearances to the contrary notwithstanding. It is the belief that organisms such as Taenia solium, the pork tapeworm, fulfill a function in the great, but unspecified, scheme of things. No one wants this kind of biodiversity in or for himself, of course.
None of this implies that the destruction of species is never, often, or even usually regrettable; but that is quite another matter from the new paganism of biodiversity.