Considering Evolution as a mechanism ensures the survival of the fittest gene pools, and well over 90% of all species ever to have existed have gone extinct, is it right for humans to put such an effort into preventing species from going extinct? Obviously excluding cases where the threat of extinction comes from man made causes such as pollution or destruction of their habitat, the theory of evolution would suggest that if a species naturally goes extinct, it's for the best.
Best for whom? The enviroment may change so that a particular species of tree is no longer very successful at propagating itself. If we do nothing, it will go extinct. But it might be much better for us if we did not let that happen, because the bark of the tree contains a chemical that is highly beneficial to us.