It's not just the individuals causing the problems...Parrots in Florida came from area attractions and they never tried to recapture them, had a large macaw land on our tv antenna in '65 and bent the heck out of it... and the noise !!! and green budgies that are 10in tall are everywhere (they nest in palm trees).
These same attractions had ponds of tropical fish that the preditor birds would catch and dropped them in other ponds while cleaning them... or during heavy rains the ponds would flood and out go the fish...same thing at the tropical fish farms.
Oh yea, don't forget the government and all their wisdom (read: game & fish commission).
Used to have an old lfs here for about 40 yrs with a drainage canal beside it that had a variety of tropicals in it and they always remained close to the store ( no one ever fest up to that ) still see a few there 5 yrs and ten large storms later.
Somewhere around here I've got a 3.5ft lizard hiding (not mine).
and the D@MN chickens ( foreigners think they have to have them for luck or their religon, then they move and leave them)
Geeeese, now that I reread this I think I see the benifit of living up north, everything dies off with the cold!
Mother nature tries, but we can screw things up faster than she can fix them.
Now if I were made supreme leader of this planet..hhmmm