Esther Inglis-Arkell poses a really interesting question over at io9:
Let's say you get a device, or perhaps a biological agent, or maybe even a weirdly specific wizard-wand. It has one function. If you use it, all the non-native species in your country would be gone. Would you use it? And if you're on the fence, what conditions would sway you either way?
Right now I'm in the middle of reading E. O. Wilson's The Future of Life, so my first response is a rapid-fire, "Of course!!"
But Inglis-Arkell points out an important element of the question: "The first thing to consider would be the method by which they would 'be gone.'" The point is made that there would be a variety of problems presented, based on how integrated the species is in its non-native environment, and how dependent other species (ahem, humans) have become on them. If so many domestic animals -- non-native to a country but raised as livestock for hundreds, if not thousands of years -- up and disappeared, there would be a lot of very hungry people. Similarly, many food crops would no longer be available.
And other questions to consider is how long a species is present in a place before it is considered native enough to be allowed to stick around. If it has been located somewhere for thousands of years, would it be part of the species that need to vanish at the wave of this wand? For instance, would domestic dogs be allowed to stay in North America? North American people were breeding domestic dogs as far back as 9,400 years ago. Would only ancestors of these breeds get to stay? Even if the gray area around this were accepted, the vast majority of dogs would have to high-tail it out of the U.S.
And as Inglis-Arkell notes, what would happen with the ecological niches left behind? Many invasive species have killed off native species that competed in its niche, so how might an area be affected if there were not species available who could take up the roles? Or what if a native species went nuts filling the newly opened niche, causing new problems? Just consider the Hawaiian Islands alone, where the majority of flora and fauna is invasive, with so many native species pushed into extinction. What would these islands look like, and how would they function after a wave of this magical wand? (And, importantly, as we question above, humans likely wouldn't be allowed to stick around on the islands to see the outcome!)
The question is fascinating and the answer is surprisingly complex. But even after thinking for awhile on the possibilities, what would you do? Would you wave that magic wand and vanish starlings from the North American skies, clear all the rats and pigs off of Pacific islands, and disappear zebra mussels from lake and river beds?