Invasive species are a serious threat to endemic Australian species, and an ongoing cost to Australian agriculture. Numerous species arrived with European maritime exploration and colonisation of Australia and steadily since then. There is ongoing debate about the potential benefits and detriments of introduced species; some experts believe that certain species, particularly megafauna such as deer, equids, bovids, and camels, may be more beneficial to Australia's ecosystems than they are detrimental, acting as replacements for extinct Australian megafauna.Xavier La Canna, September 12, 2017, "Australia's introduced animals: Eradication programs under the spotlight", Australian Broadcasting CorporationMonique Ross and Ben Cheshire, November 4, 2024, Meet the defiant grazier using feral donkeys to regenerate his land at Kachana Station in an 'illegal' experiment, Australian Broadcasting Corporation
Management and the prevention of the introduction of new invasive species are key environmental and agricultural policy issues for the Australian federal and state governments. the management of weeds cost A$1.5 billion on weed control and a further $2.5 billion in lost agricultural production over the course of a year.Impact of Weeds Department of the Environment and Energy. Retrieved 22 November 2016.
Causes Both geological and climatic events helped to make Australia's flora and fauna unique.Egerton, pp. 14, 20. Australia was once part of the southern supercontinent Gondwana,Egerton, p. 20. which also included South America, Africa, Arabia, India, Antarctica and Zealandia. Gondwana began to break up 140 million years ago (mya); at 50 mya, Australia separated from Antarctica, and was relatively isolated until the collision of the Indo-Australian Plate with Asia in the Miocene epoch, 5.3 mya. As Australia drifted, it was isolated from the evolutionary pressures in the rest of the world. Other examples of island isolation include Madagascar, New Zealand, Socotra, the Galapagos and Mauritius. The geographic isolation of Australia created a sharp division between Australian fauna and Asian fauna at the Wallace line.
Humans arrived in Australia between 80,000 and 45,000 years ago, living alongside megafauna for 20,000–25,000 years before the megafaunal extinctions that were likely caused by, or partly contributed to by, late Pleistocene climate change; however, the full reason for the extinctions is still unclear and human hunting or habitat changes through fire-stick farming may also have contributed to the extinctions. This left Australia with much of its keystone species extinct, leaving the ecosystems altered and far more vulnerable to invasion.
Dingoes probably arrived in Australia between 5,400 and 4,600 years ago, long after the first humans, spread rapidly across the continent and probably contributed to the extinction of even more native species such as the thylacine and Tasmanian devil. The current period of invasive species introduction began in 1788 with the arrival of the first European settlers. The population density in Australia beyond the coastline and major cities has been very low since the arrival of European settlers, and there are large tracts of land where it is very difficult for people to manage even large feral animals like camels, horses, donkeys and water buffalos.
Invasive species
Fungi and bacteria Invasive fungi and bacteria in Australia affect many native plants and animals and agricultural crops. Citrus canker was found twice in the Northern Territory in the 1900s, and was eradicated each time. In 2004, an outbreak of citrus canker occurred in Australia, and many Queensland citrus orchards have been burned to remove the disease. The destruction worked; however, the disease was once again detected in April 2018 and confirmed in May 2018 in Northern Territory and Western Australia. The oomycete Phytophthora cinnamomi, commonly known as wildflower dieback or jarrah blight, has created a massive problem in some types of native vegetation – especially jarrah forest and banksia woodland.National Phytophthora cinnamomi . Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group. 2005 Global Invasive Species Database. Retrieved 17 July 2012.
Animals Australia is host to 56 introduced invasive vertebrate animal species. They can be categorised in the following ways:
Invasive – species has a tendency to spread their range into new areas or plague their range Ferals – defined as animals imported for domestic purposes (i.e. pets, recreational use – such as hunting – or beasts of burden) that have gone wild. Pests – animals that have a direct effect on human standard of living or the environment/ecosystems in areas where they are present, have a high rate of reproduction and are difficult to control
Animals causing most public concern and economic and ecological damage include:
Image Species Introduced Reason Introduced from Distribution Threat level Estimated proliferation Main control measures Notes / ref Blackbuck(Antilope cervicapra) 1900s (Western Australia)1980s or 1990s (Queensland) Livestock India Western AustraliaFormerly present in Cape York, Queensland ? Unknown Shooting Cat(Felis catus) 1849 Pets Europe Throughout Australia, except in tropical rainforests (extensive) Extreme Domestic: 3.8 millionFeral: 2.1 to 6.3 million Barrier fencing, shooting, trapping, toxic pellet implants. Control measures effective on small islands; less so on the mainland. Cats have contributed to the extinction of many species of mammals and birds. European rabbit (Oryctolagus cuniculus) 1857 Recreational hunting Europe Throughout Australia (extensive) Extreme 200 million + Rabbit-proof fence; Myxomatosis; Calicivirus (RHD) Prolific breeders that destroy land.Tropical fire ants (Solenopsis geminata)1800AccidentalSouth America Western Australia and Northern TerritoryMajorUnknown ?Red imported fire ants (Solenopsis invicta)2001AccidentalSouthern USASouth East QueenslandExtremeUnknown Movement controls for specific organic materials in fire ant biosecurity zones. Cane toad (Rhinella marina) 1935 Biological control (cane beetle) Americas via Hawaii Queensland (extensive), the Northern Rivers (New South Wales), the Top End (Northern Territory), the Kimberley Extreme 200 million + Culling; trapping;Cane Toad Home. Frogwatch. Retrieved 17 July 2012. geneticKilling off the cane toad . Institute Molecular Bioscience. Retrieved 17 July 2012. (under research) Prolific breeders and bufotoxin kills native animalsThe Feral Cane Toad (Bufo marinus) – Invasive species fact sheet Red fox (Vulpes vulpes) 1855 Recreational hunting Europe most of mainland Australia; small numbers in Tasmania Extreme 7.2 million + 1080 baiting; hunting Elusive prolific predator of native animals and livestock. Feral goat (Capra hircus) 1840 Domestic livestock Unknown Throughout Australia (extensive) High more than 2.6 million in 1996 Feral pig (Sus scrofa) 1788 Domestic livestock Europe Throughout Australia, except in deserts (extensive) High up to 23.5 million in 2011 Musters, ground and helicopter culling, trapping, poisoning, fencing Prolific breeders that destroy land and have the potential to spread disease Feral donkey (Equus asinus) 1866 Pack and haulage animals Europe Throughout Australia (extensive) Medium to high up to 5 million in 2005 Musters, ground and helicopter culling, fertility control Grazers that damage sensitive lands Dromedary camel (Camelus dromedarius) 1840 Beast of burden India Outback Medium to high 300,000 in 2013 Helicopter culling Grazer, though arid Australian conditions suit the camel perfectly. Brumby (Equus ferus caballus) 1788 Farm and utility work Europe; some later imports from South Africa and Indonesia Throughout Australia (extensive) Medium to high more than 300 thousand Musters, ground and helicopter culling, fertility control Grazers that damage sensitive lands Banteng (Bos javanicus) 1849 Domestic livestock Indonesia Garig Gunak Barlu National Park Medium 8,000 - 10,000 Hunting Environmental damage – soil erosion, channelling of floodwaters, increased intrusion of saltwater into freshwater habitats and destruction of wetland vegetation. Common ostrich (Struthio camelus) 1980s Farming for meat, feathers, oil and eggs South Africa Found only in outback South Australia near the Birdsville Track Medium 20,000 None due to them being rare in Australia. All wild ostriches in Australia are descendants of escaped farmed populations in the 1980s. Only one ostrich farm is active in Australia now, Hastings Ostrich Farm in VictoriaLysaght, Gary-Jon, Ostriches roam the outback after failed attempts to farm the flightless birds ABC News, 2 September 2018. Retrieved 10 January 2021. Water buffalo (Bubalus bubalis) 1829 Domestic livestock Indonesia Top End Medium 150,000 in 2008 Hunting Environmental damage – soil erosion, channelling of floodwaters, increased intrusion of saltwater into freshwater habitats and destruction of wetland vegetation.The feral water buffalo (Bubalus bubalis) . Fact Sheet. Department of Sustainability, Environment, Water, Population and Communities. Retrieved 17 July 2012. Indian palm squirrel(Funambulus palmarum) ? Zoos and pets India Perth (feral)New South Wales (pets) ? ? ? Northern palm squirrel(Funambulus pennantii) ? Zoos and pets India Perth (feral)New South Wales (pets)Feral populations formerly present in Sydney (until 1976) and Melbourne ? ? ?
Control
Various programs exist to control invasive species in Australia. A cane toad control program aims at preventing the spread of the species towards Darwin and Western Australia, and involves trapping. Red Foxes, feral cats, feral dogs and feral pigs are often baited, although the use of 1080 (sodium fluoroacetate) is also known to affect native animals such as the quoll and Tasmanian devil, though the most common and effective method is shooting. 1080 is ideal in the south-west of Australia because a native plant contains the same toxin – therefore most native animals have developed immunity to it. Other species are either open to hunting as a sport (such as the deer) or subject to government sponsored culling programs. Dromedary Camels and Water buffalo are often shot from helicopters.
Bounties Several bounty programs have assisted in the eradication of larger sized pests in Australia.
Ironically, many early bounties were paid for the extermination of native species that were considered a pest to farmers. The Tasmanian tiger or thylacine was one such program that caused extinction, whilst the Tasmanian devil, spotted quoll, and Tasmanian wedge-tailed eagle all became seriously threatened by bounties.
At various times, bounties have been in place for invasive species such as wild-living domestic dogs (including the dingo) and fox. A beer-for-toads bounty has been publicised for cane toad control in the Northern Territory.
In 2002, a Victorian Fox Bounty Trial began to test the efficacy of fox bounties which have been in place intermittently since 1893 (only 30 years after introduction). The study showed no reduction in fox impacts, and that the project may even have been counterproductive. The evaluation also found that a sustained annual reduction of 65% is required to achieve real declines in red fox populations.
Feral cat bounties in Queensland have also been considered to counter the growing problem. The dingo is subject to various controversial bounty systems in Australia. The Australian dingo was itself introduced before European settlement, yet has been considered native of the mainland in most cases both the pure breeds and the dingo-dog hybrids are considered pests to livestock.
Invasive insects and terrestrial arthropods