<<I do however question the underlying assumption that in any given habitat the species now present somehow belong and new species do not, as if we have reached the end of evolution. Some species thrive and some falter, species arise and perish. So it goes.>>

I guess one’s response to this ethical issue depends in part upon what one thinks or cares about biodiversity loss, about the “ecosystem services” provided by such diversity, etc.  even if only from an anthropocentric perspective.  See IUCN re. invasive species - https://www.iucn.org/theme/species/our-work/invasive-species

“An alien species is a species introduced by humans – either intentionally or accidentally - outside of its natural past or present distribution, however not all alien species have negative impacts, and it is estimated that between 5% and 20% of all alien species become problematic. It is these species that are termed ‘invasive alien species’ (IAS)….Invasive alien species are a major driver of biodiversity loss.” 

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