Removing invasives is more a human preference than a scientifically grounded prerogative, argues Mark Davis, an ecologist at Macalester College in St Paul, Minnesota. "There is a huge amount of arbitrariness here," he says. "Can't we just forget about where they came from, identify species that are causing us problems according to our values, and then deal with them?" (From Nature.)I, for one, can't forget. I like places to be distinct. I enjoy visiting distant places because they look so different from home, and because they reflect so different histories. Invasive species are ruining the distinctiveness of places. I dislike invasive species and, yes, this is an arbitrary preference.
The fact that invasive species are causing problems other than erasing the marks of history and eroding the diversity of landscapes is a wholly different matter. In this regard, Mark Davis is right that invasive and native species deserve the same treatment.
Do invasive species cause more such problems than native species? Well, that is the question. We don't know the answer because it just doesn't cross the minds of ecologists to argue that a "native" species living in its "natural" environment is doing harm because it increases fire frequency, decreases fire frequency, depletes underground water, clogs waterways, decreases water quality, or displaces other native species. We avoid applying this kind of utilitarian analysis to natural ecosystems. We do apply utilitarian analyses to native species and ecosystems, but biased ones that systematically ignore their negative effects.