The concept of ecosystem services is a way of visualizing the instrumental value that nature has for human beings. Most ecosystem services can be performed by more than one species. This fact is sometimes used as an argument against the preservation of species. However, even though substitutability does detract from the instrumental value of a species, it also adds option value to it. The option value cannot make a substitutable species as instrumentally valuable as a non-substitutable species, but in many (...) cases, it can add enough value to make the species more valuable than the projects that threaten its existence. (shrink)

Species are thought by many to be important units of evolution. In this paper, I argue against that view. My argument is based on an examination of the role of species in the synthetic theory of evolution. I argue that if one adopts a gradualist view of evolution, one cannot make sense of the claim that species are units in the minimal sense needed to claim that they are units of evolution, namely, that they exist as discrete entities over time. (...) My second argument is directed against an appeal to Eldredge and Gould's theory of punctuated equilibria to support the claim that species are units of evolution. If one adopts their view, it may be possible to identify discrete temporal entities that can plausibly be termed species, but there is no reason to claim that those entities are units of evolution. Thus, on two plausible interpretations of the role of natural selection in the process of evolution, species are of no special importance. I then consider some of the reasons why species have been thought to be important evolutionary units by many contemporary evolutionary biologists. Finally, I discuss briefly the implications of this conclusion for evolutionary biology. (shrink)