According to classical utilitarianism, the only intrinsic good is happiness; the only intrinsic bad is pain. That implies no intrinsic value in preserving nature, that preserving an endangered plant is valuable only if it benefits humans or other animals. Intuitively, that seems wrong but perhaps I shouldn't trust my intuition here.
Peter SingerIn appropriate circumstances we are justified in using humans to achieve goals (or the goal of assisting animals).
Peter SingerThe newspapers do little better. Their coverage of nonhuman animals is dominated by "human interest" events like the birth of a baby gorilla at the zoo, or by threats to endangered species; but developments in farming techniques that deprive millions of animals of freedom of movement go unreported.
Peter SingerPain is pain, and the importance of preventing unnecessary pain and suffering does not diminish because the being that suffers is not a member of our own species.
Peter Singer