What are the effects of introduced species into Australia?

A successful introduced species eradication scheme is one that, once the intro. species has "done it's job" then it dies because there is no more pest/ feral organisms for it to survive on. However, some schemes are unsuccessful and the introduced species becomes a pest, a good example of this in Australia is the well known cane toad, some of the effects this organism has had on the Australian environment is that, because the toads are in fact poisonous, because of their warts, their poison has killed alot of Australia's natural, carnivorous, species, such as the chuditch, and also household pets. The toad also takes over some environments and drives out other species that live there.

Another is the magnificent brumbies, they were once farm horses for the migrants from England, but broke free and became "feral" (once domesticated) these horses also drive out other organisms not on purpose, but because of natural competition for food. They are also the main culprit for soil erosion on the hills due to their galloping along in big herds, this obviously will have a huge impact on the "compactiveness" of the soil.