"Des Higgins" wrote in message
...

[snip]

Bad means making a mess of other species which are native or
poisoning the
kids.

That is an untenable generalisation. South Africa imported, from
Australia, the insect Cactoblastus cactorum in order to destroy large
areas of prickly pear in the Little Karoo, thereby making hundreds of
thousands of acres available for grazing land.

Franz