Many animals were brought to Australia by humans. Some, such as the sheep and cattle, have been vital to the Australian economy. Others have caused serious problems to the Australian environment, native animals and plants. This has led to the demonisation of these hapless creatures and attempts to eradicate them in some very cruel and inhuman ways.
Humans have been the most destructive animals ever introduced to Australia.
Australia has been isolated and insulated from the rest of the world for millions of years. In its isolation many specialised plants and animals evolved that were uniquely adapted to its particular environment. Up until the arrival of Europeans settlers starting in 1788, only one non-indigenous animal was introduced to Australia. This was the dingo which arrived about 4,000 years ago. Since 1788 however more than 25 mammals, 20 birds, 4 reptiles, 1 frog, 34 fish, hundreds of marine species, an unknown number of invertebrates and more than 2,800 weeds have been introduced to Australia.
The introduction of foreign plants and animals have sometimes had unforeseen impacts on native flora and fauna. These impacts have ranged from negligible to catastrophic. Many of these introduced species damage and degrade the ecosystem, bring new diseases, prey on native species, and compete with native plants and animals for food and shelter.
Until Europeans came in 1788, there were no hoofed animals (like horses, cattle, goats, deer etc.) in Australia.
Also Rats and mice were the only animals that the Europeans didn't bring intentionally. They arrived in Australia as stowaways on sailing ships.
It is important to remember that these introduced animals never attempted to come to Australia on their own. We humans brought them to Australia without due consideration for the impacts of our actions. These animals are only following their natural instincts to survive into their new environment. Yes, some have killed native plants and animals. Yes, they out-compete the natives. But we brought them here and failed to manage them from the very outset.
Some ludicrous unsubstantiated claims have also been made. For example, it is claimed that feral cats kill 20 billion Australian native species each a year! This is surely scaremongering. Sure, there is an issue with introduced species, but very little unbiased scientific research has been done to determine the true impact of introduced animals on the Australian ecosystem.
The impacts of the various introduced animals on the the Australian ecosystem have been broadly classified below. Sometimes an animal can be in more than one group. For example the rabbit is classified as both feral and a pest.
Beneficial - These species have been useful to humans or the environment.
Benign - These creatures have had no noticeable adverse impact on the Australian ecosystem.
Invasive - species have a tendency to spread their range into new areas
Feral - Domestic animals brought to Australia that have gone wild and significantly impact the ecosystem.
Pests - These animals have a direct negative effect on the Australian ecosystem and are difficult to control.