Invasive specie
The boa constrictor in Florida was mentioned in another thread .many species have been introduced by humans and the results have been disasterous .
E.g. The cane toad in Australia
Australia has no end of introduced pests ( not even counting the human variety
)
The cane toad was brought in to eat the cane beetle but found the local fauna more to its taste .
In the Uk we have lots of invaisve species some are pretty like the Munjac deer others are a disasterr like Japanese knotweed.