> We should define "invasive species" to mean "species which gets transported to another ecosystem via means beyond its control or natural behavior" and therefore exclude humans.
Why?
And what is the fixed reference point that defines "natural" behavior in contrast to what I would assume you would call "unnatural"? Isn't everything that happens within the constraints of the earth's ecosystem by definition "natural"?
> or a spider which accidentally hitches a ride on a piece of driftwood and populates a distant island.
How and why is that different? If conditions in the natural ecosystem result in the spider ending up in the new island, and its extant traits prove to be a good match to the ecosystem there, resulting in it thriving and reproducing extensively, how is that more like the toad and than the human?
It seems like you are drawing distinctions based on the particular normative ideas that you hold, which are in turn both antropocentric at the macro level, and subjective to you specifically at the micro. I'm not sure this normative framework is a good analytical model for understanding objective reality.