I'd never heard the word michaelr until I saw it on here. They've always been 'coypu' to me.
That's the problem when a species not indigenous to an area is introduced. It will cause changes in the habitat and native population.

Here in UK the arrival of the grey squirrel reduced the population of our red squirrels markedly. The muntjac, fallow and Chinese water deer (not native to UK) have caused a lot of damage to woodlands. They nibble away at young trees and also remove the bark all around the trunk, eventually killing the tree.
There's also the harlequin ladybird, which is affecting our seven native ladybird species.
When I was last up in Edinburgh a couple of years ago, I saw quite large areas of that wretched Japanese knotweed. The authorities had blasted it with everything they'd got (strong chemical herbicides) but it seems it still bounces back. If there was another nuclear war, after the Apocalypse I bet there would be shoots of Japanese knotweed jauntily poking through the blackened earth!