“All species have a value to nature and thus in turn to humans,” says Dr Stuart:
Although the value of some species may not appear obvious at first, all species in fact contribute in their way to the healthy functioning of the planet.
This is just silly
Nature doesn't 'value' things.
And the healthy functioning of the planet does not seem to have been affected by any of the previous extinctions.
If we know or suspect something might be useful to us it is entirely reasonable to try to preserve it. Same goes for cute things - if we want pandas, well, fine, let's try to keep some (might be simpler to breed fat raccoons or something but whatever people want).
If there's anything ugly and of no, or unknown and unguessable, utility then I don't see what justifies the impulse to interfere with nature and prevent its extinction but if anyone wants to try I don't suppose it would do much harm either.