As essentially an anthropocentrist I am entirely comfortable with the notions of useful and harmful species (which correspond with ecosystem services and disservices, respectively). However, I fiercely oppose the notion of “(invasive) alien” species, which is quite popular in the conservation discourse. Notwithstanding its obvious popularity, I think that it is flawed in being xenophobic and arbitrary.
(Invasive) alien species, also called neobiota, neophytes, neozoen, exotics, non-native or introduced species are “species living outside its native distributional range, which has arrived there by human activity, either deliberate or accidental.” In journals devoted to conservation biology, ecology and environmental management, you can find a lot of papers that include lists of (invasive) alien species, instructions how to get rid of them and how to prevent their arrival in the first place. While in the scientific discourse the focus is mostly on invasivity, the typical environmentalist considers all non-native species potentially “bad” for native ecosystems. I consider this what might be called phyto- or zoo-xenophobia. This is not to say that some species are not harmful – they often are, as for example giant hogweed. What I am opposed to is the framing of the problem as harm from “non-native” species, which puts into suspicion all “aliens” – a stunning parallel to xenophobia in human relations. Meanwhile, there are many harmless or even beneficial neobiota out there, just as there are harmful natives.
An important point is the non-obvious answer to the question of what constitutes harm. Basically, there are two possibilities. Either one means harm to human health or, more generally, human well-being (as in the cases of ambrosia and giant hogweed), or harm to ecosystems. This is essentially the distinction between anthropocentric and non-anthropocentric perspectives, respectively. The former approach has some usefulness, though not when it is framed in terms of natives (harmless) vs. non-natives (harmful), for reasons outlined above. The latter is absurd regardless of the ethical standpoint invoked, as it implies a nonrealistically static view of ecosystems. Ecosystems change continually, this is the natural way things work – sometimes called evolution. The static point of view can only be defended by means of the exclusion of homo sapiens from nature, because then unintended evolutionary changes triggered by the introduction of “alien” species could be considered an “abhorration”. I don’t think, however, that this is a defensible standpoint – human beings are part of nature, our interactions with other species differ from those between themselves only in terms of magnitude. Still, if the focus is on nature and natural processes, our actions constitute nothing else than another evolutionary pressure. It would be highly arbitrary to say that evolution and natural selection are OK, unless they are triggered by human activity.
Last but not least, there is the question of what constitutes an alien species. Ecosystems are dynamic systems, which change at a fast pace even without human activity. Yes, the latter increases that pace because we are an extremely mobile species and take other species with us – sometimes with intent, more often without – wherever we go. Still, when talking about alien species, there is no obvious reason why this should be restricted to species introduced by humans (not least because it is not always clear how large the human contribution was in a specific case). Also, many species that we now consider native are in fact alien – if we look back far enough. In some countries, such as Great Britain, anything is “non-native” if it has arrived after 1492 – which is an extreme case of arbitrariness.
In summary, I think that the concept of (invasive) alien species is heavily flawed in many respects and should thus be abandoned. And I say that as an anthropocentrist, even though, as shown above, I believe that anthropocentrism supports at least some components of the alien species concept, particularly a more or less coherent harmfulness concept. I don’t see how it could be defended in any respect under a different, more encompassing ethical perspective.