Australia's threatened species
Box 2 | The aliens
Many species have been brought into Australia deliberately or accidentally. In the 1800s animals and plants were deliberately brought in from Europe so that people would feel more 'at home' here.
Species from other countries are technically referred to as 'alien' or 'exotic'. The word 'introduced' is used to refer to species that occur outside their previous, natural range, and so can be used for alien species as well as for native species that have been moved to regions where they did not occur naturally – for example, koalas in Western Australia.
Alien species often thrive in their adopted homelands because they have escaped the competitors, parasites and predators that kept them in check in their countries of origin.
Feral animals are destructive
'Feral' is used to refer to animal species that are domesticated but which have been able to establish wild populations. Rabbits, foxes, cats and goats are particularly successful. The extent of the effects of feral cats on native animals is still under investigation. It is known that feral cats prey on various native bird and mammal species. Foxes are also serious predators and have been implicated in the decline, and possibly extinction, of some of our native species. Goats and rabbits have affected native vegetation cover and compete with native fauna for scarce resources. In some areas rabbits take over the burrows of native animals such as bilbies and bandicoots.
Other major feral mammals are dogs, horses, water buffalo, pigs, donkeys, cattle, sheep and camels. Rats and house mice were probably brought in accidentally but have been very successful.
Other problem species
Exotic fish are common in most waterways. Trout, goldfish and European carp are particularly widespread. Exotic fish have been implicated in the decline, endangerment and extinction of several native fish species.
Many invertebrates have also been introduced, but less is known of their effects because they are less obvious. However, some insect immigrants are very worrying. The European wasp, for example, probably came here as recently as the 1970s and is now spreading rapidly in south-eastern Australia. The wasps prey on native insects, including some which are important for pollinating native plants or crops.
Exotic plants have also thrived, with non-native species accounting for about 15 per cent of our flora. Many of these alien species invade native vegetation and so are a serious cause of habitat change, which may in turn threaten native animals in the area.
Boxes
Box 1. The hidden species at risk
Box 3. Australia's biodiversity
Box 4. The mathematics of reserve systems
Box 5. Survival of the cutest?
Related site
Feral animals in Australia (Australian Government Department of Sustainability, Environment, Water, Population and Communities)
Australian pests – photo gallery (Australian Broadcasting Corporation)
Page updated January 2012.