It's really because irresponsible people release non-native animals into the wild.
In many cases, the animals simply perish. In other cases (far too many) the animals are well-adapted enough to a new environment, that they sometimes breed prolifically. In the absence of their normal predators, they can cause serious problems and wreak havoc on native ecosystems.
The list is a very long one: striped zebra mussels, pretty much everywhere, Asian carp in the Great Lakes, red-eared sliders pretty much everywhere, cane toads in Australia, Burmese pythons in the Florida Everglades, brown snakes in the tropics, Nutria in Europe,...I could go on - just ask Hawaii! Islands are particularly vulnerable. And we are not even mentioning plants like Kudzu and 100's of others.
Then, there is a certain virus making its way around the globe...
I'll bet the UK certainly has restrictions on many species...or they should!
I wish you a Happy New Year!
