Australia’s Major Invasive Species
Taking species from natural environments and introducing them to foreign ones can, and has caused many unintended consequences. The following cases have caused considerable destruction of Australia’s environment and natural ecology. While the issue needs to be addressed at a national level, individual farmers may be able to resist some pests’ damaging effects through the use of protective canopies
Cane toads were introduced from their native South America, to control the native cane beetle, which damages sugar cane crops. In addition to being unsuccessful in this pursuit, the cane toad has gone on to become a major national menace. From their limited introduction in Northern Queensland in 1935, they have procreated rapidly, up to a population of over 200 million. They have also spread dramatically, right through Queensland, into New South Wales, and west into the Northern Territory.
Unlike the cane toad, foxes were introduced to Australia for leisure, namely hunting, in the mid 19th century. Ironically, more hunting than ever is needed to try and reduce the out of control population of feral foxes. Baiting is also used to try and control a population numbering over 7 million. Foxes have been responsible for the extinction of several native Australian animals, for which foxes became a predator.
Around the same time that foxes were being introduced for hunting, so too were rabbits, for the same purpose. By eating native plants, rabbits have been responsible for exposing topsoil, making land susceptible to erosion. The use of Myxomatosis helped reduce Australia’s rabbit population from an estimated 600 million to 100 million. Unfortunately, rabbits became resistant to myxomatosis and populations recovered to possibly 200-300 million. A similar experience unfolded with the accidental release of calicivirus, which reduced rabbit populations, until rabbit populations became resistant.
Cats have been in Australia since the time of the convicts, and continue to be a popular pet. With cats being very adept at catching small animals, it is believed that Australia’s large feral cat population has had a very negative effect on Australia’s native fauna. In an interesting twist, feral cats have, however, been helpful in also feeding off wild rabbits, another introduced pest. Feral cats cover much of Australia’s territory, with the exception of regions with dense rainforest.
Most Australians will recognise the ubiquitous Indian Mynah, so prevalent due to its prolific breeding. It was introduced into Australia to control locust plagues. Indian Mynahs can disrupt native bird populations, by forcing them from their eggs and nests. Common starlings and rock pigeons are also introduced pests.
Australia’s native freshwater fish populations have been decimated by the introduction of more powerful species from overseas into local river systems. Such fish include very damaging carp and trout, as well as redfin perch and mosquitofish.
Other types of introduced pests include insects such as wasps, bees and fire ants. Marine pests include mussels and the crown of thorns starfish, the latter being extremely deadly to coral on the Great Barrier Reef.
On the flora side of things, introduced weeds also threaten elements of Australia’s natural environment. While many programs aim to try and bring most of the above pests under control, managing their negative effects will be an ongoing battle.
It can be seen that introduced species have had a devastating effect on Australia’s environment. Without natural predators, many species like the Indian Mynah are free to breed prolifically. At least bird netting is effective in protecting valuable produce against attacks and damage by that particular bird.