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Invasive species in Australia are a serious threat to the native biodiversity, and an ongoing cost to Australian agriculture. [1] Numerous species arrived with European maritime exploration and colonisation of Australia and steadily since then. [2] There is much 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. [3] [4]
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 costs A$1.5 billion on weed control and a further $2.5 billion yearly in lost agricultural production. [5]
Both geologic and climatic events helped to make Australia's flora and fauna unique. [6] Australia was once part of the southern supercontinent Gondwana, [7] 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 [8] [9] [10] before the megafaunal extinctions that were likely caused by, or partly contributed to by, late Pleistocene climate change; [11] [12] 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 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.[ citation needed ] 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. [13]
Australia is host to 56 introduced invasive vertebrate animal species. They can be categorised in the following ways:
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 Australia Formerly present in Cape York, Queensland | ? | Unknown | Shooting | [14] | |
Cat (Felis catus) | 1849 | Pets | Europe | Throughout Australia, except in tropical rainforests (extensive) | Extreme | Domestic: 3.8 million [15] Feral: 2.1 to 6.3 million [16] | Barrier fencing, shooting, trapping, toxic pellet implants. [17] Control measures effective on small islands; less so on the mainland. | Cats have contributed to the extinction of many species of mammals and birds. [18] | |
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 ) | 1800 [19] | Accidental | South America | Western Australia and Northern Territory | Major | Unknown | ? | [20] | |
Red imported fire ants ( Solenopsis invicta ) | 2001 | Accidental | Southern USA | South East Queensland [21] [22] | Extreme | Unknown | Movement controls for specific organic materials in fire ant biosecurity zones. [23] | ||
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; [24] genetic [25] (under research) | Prolific breeders and bufotoxin kills native animals [26] | |
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. [27] | |
Feral goat (Capra hircus) | 1840 | Domestic livestock | Unknown | Throughout Australia (extensive) | High | more than 2.6 million in 1996 [28] | |||
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 [29] | |
Feral donkey (Equus asinus) | 1866 | Pack and haulage animals | Europe | Throughout Australia (extensive) | Medium to high | up to 5 million in 2005 [30] | 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 [31] | Helicopter culling | Grazer, though arid Australian conditions suit the camel perfectly. [32] | |
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 [33] | |
Banteng (Bos javanicus) | 1849 | Domestic livestock | Indonesia | Garig Gunak Barlu National Park | Medium | 8,000 - 10,000 | Brucellosis, tuberculosis, 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 Victoria [34] | |
Water buffalo (Bubalus bubalis) | 1829 | Domestic livestock | Indonesia | Top End | Medium | 150,000 in 2008 [35] | Brucellosis, tuberculosis, hunting | Environmental damage – soil erosion, channelling of floodwaters, increased intrusion of saltwater into freshwater habitats and destruction of wetland vegetation. [35] | |
Indian palm squirrel (Funambulus palmarum) | ? | Zoos and pets | India | Perth (feral) New South Wales (pets) | ? | ? | ? | [36] | |
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 | ? | ? | ? | [36] |
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.
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.[ citation needed ] 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.[ citation needed ]
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. [37]
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).[ citation needed ] 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.[ citation needed ]
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.[ citation needed ]
Insects are the second costliest class of invasive species in Australia, behind only the mammals. Fire ants in Australia (Solenopsis invicta) are estimated to cost A$ 1.72 billion (2021) (equivalent to A$1.83 billionor US$ 1.33 billion in 2022) [38] annually, making up 71% of the total costs of invasive insects. This is followed by the Queensland fruit fly (Bactrocera tryoni) making up 12% of the total costs, the Pacific fruit fly (Bactrocera philippinensis) making up 9%, and the bollworm (Helicoverpa) making up 7%. [39]
Yellow crazy ants (Anoplolepis gracilipes), black Portuguese millipedes (Ommatoiulus moreletii), Western honey bees (Apis mellifera), and European wasps (Vespula germanica; known elsewhere by the common name "German wasps") are considered to be problematic species.[ citation needed ] The elm leaf beetle (Xanthogaleruca luteola), discovered in Victoria in 1989, devastates exotic elm trees, [40] themselves imported, and a parasite wasp species as well as the beetle's natural enemy the parasitic fly ( Erynniopsis antennata ) were in turn introduced in 2001 in an effort to control the pest.[ citation needed ]
The red imported fire ant in particular, with its venomous stings, poses a direct threat to human lifestyle. Although control is extremely difficult and spread quickly, the species is currently effectively quarantined to South East Queensland. [41]
Both the honey bee and European wasp are well established and now impossible to eradicate in Australia. Honey bees take over potential nesting hollows for native animals and are very hard to remove once established.[ citation needed ] [42]
The yellow crazy ant is currently quarantined to Christmas Island where it has had a significant environmental impact. [43] The primary impact is the killing and displacing of crabs on the forest floor.
Introduced birds considered pests include the common myna, the common starling, the spotted dove and rock pigeon (common pigeon). [44]
Initially introduced to control locust plagues, [45] the Indian myna breeds prolifically in urban environments in the eastern states. The myna poses a serious threat (such that it has been listed in the World Conservation Union's world's 100 worst invasive species). [46] The bird has caused human health concerns due to the spread of mites and disease. It has also been known to force native birds and their eggs from their nests. [47]
The rock pigeon in particular has acidic faeces and can damage human property, including historic stone buildings. [48]
Historically, control programs have struggled to curb the expansion and proliferation of invasive bird populations in Australia. A new program in Canberra has reversed this trend regarding mynas. Since 2006, the Canberra Indian Myna Action Group (CIMAG) has implemented an effective control scheme, based upon large-scale trapping conducted by volunteers. As of June 2013, the Action Group has recorded over 45,000 myna captures in the Canberra region since 2006. This has reduced the myna's prevalence in the Canberra region from a ranking of third most prevalent bird species in 2006, to twentieth in 2012. This has correlated with anecdotal evidence of increased nesting activity and prevalence of native species in the Canberra region. Other volunteer organisations in Australia have begun to adopt the CIMAG model with similar success.
Starlings and sparrows are currently closely monitored in south-eastern Western Australia.
Despite the number of rock pigeons, many people continue to feed the birds bread crumbs and assist them to breed in great numbers. It is not illegal to feed pigeons in Australia, and many local proposals to cull pigeons have been rejected.
Programs promoting indigenous plantations to attract native birds are an alternative method of promoting native species rejuvenation though this has caused issues with the explosion in the Noisy miner population. [49]
Invasive freshwater fish species in Australia include carp, brown trout, rainbow trout, redfin perch, mosquitofish (Gambusia spp), [50] weather loach, and spotted tilapia among others. Some introduced freshwater fish species have had devastating impacts on Australia's endemic freshwater fish species and other native aquatic life. For example, in much of south eastern Australia's freshwater systems introduced carp (often incorrectly called "European" carp) dominate the lowland reaches, [51] while introduced trout species almost completely dominate the upland reaches. While the damaging impact of carp is well recognised, little in the way of control measures have been employed to control their spread. Their ability to colonise almost any body of water, even those previously considered to be beyond their physical tolerances, is now well established.[ citation needed ]
A number of marine pests have arrived in Australia in the ballast water of cargo ships. Marine pests include the black-striped mussel (Mytilopsis sallei), the Asian mussel, the New Zealand green-lipped mussel, and the European shore crab. The Northern Pacific seastar in Tasmania, Inverloch, and Port Phillip has caused much localised environmental damage.
Weeds invade natural landscapes, waterways, and agricultural land. Originally, plants were most likely to be considered weeds if they had a direct economic impact, especially on agricultural production. However, growing environmental consciousness since the 1970s has led to the recognition of environmental weeds; plants which have adverse effects on the natural ecosystem of an area. [52] A list of Weeds of National Significance (WONS) was created in 1999 and updated in 2012 and now has 32 taxa.
Not just the prickly pear: Hudson's Pears - Cylindropuntia tunicata and C. rosea - are also cacti of agricultural significance in Queensland. [53]
Weed management costs the Australian economy A$4 billion yearly; weeds are considered the second greatest threat to biodiversity after land clearing. Almost half of Australia's 220 declared noxious weeds (under legislation) were introduced deliberately, one third of these as garden ornamentals.
The management of invasive species is carried out by individuals, conservation groups, and government agencies.
The Australian Quarantine and Inspection Service is responsible for ensuring that no new species with the potential to become invasive species enter Australia. To raise public awareness, Australian Quarantine has featured Australian celebrity nature lover Steve Irwin on a series of television commercials, with the message Quarantine – Don't mess with it.[ citation needed ]
Several scientific bodies are involved in research for the control of invasive species. The CSIRO has released several successful biological pest control agents and developed chemical agents for pest and weed control. For example, the CSIRO released myxoma virus to control wild rabbits in Australia. Rabbit haemorrhagic disease escaped containment from an Australian Government research facility and spread across Australia. Rabbit hemorrhagic disease was subsequently legalised for the control of wild rabbits. The moth Cactoblastis cactorum was introduced for the control of prickly pear, and the salvinia weevil Cyrtobagous salviniae for the control of aquatic weed Salvinia . More doubtful biological controls were the cane toad, which was introduced to control the sugar cane destroying cane beetle; instead the cane toad ate anything and everything else—the beetle was not its preferred food source given choice. The cane toad in Australia has become the biological control that is most infamous for having been a complete failure as well as becoming an environmental nightmare. Walter Froggatt, an economic entomologist, warned of this likelihood at the time. [54] It has also led to much public concern and caution when considering the introduction of new biological controls.[ citation needed ]
Another example of a poorly researched introduced biological control is the sap sucking lantana bug (Aconophora compressa) also from South America that was introduced into Australia in the 1995 to eat the lantana. Unfortunately, the lantana bug also attacks other trees including fiddlewood trees which has caused distress to some gardeners. The lantana bug had been tested for six years on 62 different plants. Aconophora compressa was the 28th insect introduced to control lantana in about 80 years.[ citation needed ]
More successfully, the Australian Dung Beetle Project (1965–1985), led by Dr. George Bornemissza of CSIRO's Division of Entomology, introduced 23 species of dung beetle to Australia in order to biologically control the pestilent population of bush flies. These flies, along with other species of fly and parasitic worm, use the dung as a breeding and feeding ground. The rolling and burying activity of the dung beetles means that the dung is removed from the pasture land, which had the effect of reducing the bush fly population by 90%, as well increasing soil fertility and quality by recycling the dung back into the soil. [55]
Cooperative Research Centres for weed management and pest animal control, have been established by the federal government. They coordinate research and funding between a number of university and government labs for research into control of invasive species.
Non government organisations have also been established to fight invasive species, for example, the Invasive Species Council (ISC). [56] The ISC are a policy, advocacy, lobbying, research, and outreach group on matters related invasive species.
Volunteer groups, such as SPRATS, have also made very significant contributions to fighting invasive species, in their case removing sea spurge from large areas of Tasmanian coastline. [57]
While negative impacts by introduced flora and fauna are often featured, some researchers argue that there could be positive aspects of introduced species to provide ecological benefits to native ecosystem in Australia. [58]
Herbivores in general may benefit local biodiversity by creating mosaics of vegetation and helping native plants to expand their ranges, and may contribute to decline wildfires; mega-herbivores most notably the feral camels may fill lost ecological niches of extinct Australian megafauna including Diprotodon and Palorchestes , where this may also apply for others (such as cattles and horses and donkeys and deers), and would also drop fire risk, [3] [4] [59] [60] [61] and smaller herbivores such as hog deer or feral goats may also suppress introduced grasses and wildfires. [62] [63]
Carnivores such as the introduced red foxes or cats may control the number of rats – and rabbits – and eradication of these carnivores may damage native ecosystem indirectly. [64] [65] [66] [67]
A 2021 study looking at the economic impact of invasive species estimated that invasive species had cost Australian farmers A$390 billion in the past 60 years, with feral cats way ahead of the pack at nearly A$19 billion. Rabbits are next, at around A$2 billion, followed by fire ants, annual ryegrass, pigs, parthenium, foxes, ragwort, cucumis melons, and common heliotrope. [68]
The World Trade Organisation specified quarantine regulations are weaker than Australia's fairly stringent regulations controlling the importing of raw produce. Following Australia's membership of the WTO, many forms of raw produce once banned have commenced import, with potentially adverse effects and controversy; for example, regarding proposals to import apples from New Zealand [69] or bananas from the Philippines. [70]
Australian quarantine regulations such as those limiting banana imports from developing economies have been recognised as protectionist trade barriers by economists including Kevin Fox, head of Economics at the Australian School of Business. [71]
The weakening of restrictions on importing raw produce into Australia mandated by the World Trade Organisation Future may pose risks of introducing exotic disease organisms. [72] Case examples include, Chytrid fungus that is threatening numerous Australian frog species with extinction and mass pilchards deaths in the Southern Ocean from 1995 onwards that are suspected to have been caused by a virus that may have been brought in with imported pilchards.
The cane toad, also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania and the Caribbean, as well as Northern Australia. It is a member of the genus Rhinella, which includes many true toad species found throughout Central and South America, but it was formerly assigned to the genus Bufo.
Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.
A feral animal or plant is one that lives in the wild but is descended from domesticated individuals. As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in some cases, contributed to extinction of indigenous species. The removal of feral species is a major focus of island restoration.
Lantana is a genus of about 150 species of perennial flowering plants in the verbena family, Verbenaceae. They are native to tropical regions of the Americas and Africa but exist as an introduced species in numerous areas, especially in the Australian-Pacific region, South and Northeastern part of India. The genus includes both herbaceous plants and shrubs growing to 0.5–2 m (1.6–6.6 ft) tall. Their common names are shrub verbenas or lantanas. The generic name originated in Late Latin, where it refers to the unrelated Viburnum lantana.
The common myna or Indian myna, sometimes spelled mynah, is a bird in the family Sturnidae, native to Asia. An omnivorous open woodland bird with a strong territorial instinct, the common myna has adapted extremely well to urban environments.
A number of introduced species, some of which have become invasive species, have been added to New Zealand's native flora and fauna. Both deliberate and accidental introductions have been made from the time of the first human settlement, with several waves of Polynesian people at some time before the year 1300, followed by Europeans after 1769.
The ecological restoration of islands, or island restoration, is the application of the principles of ecological restoration to islands and island groups. Islands, due to their isolation, are home to many of the world's endemic species, as well as important breeding grounds for seabirds and some marine mammals. Their ecosystems are also very vulnerable to human disturbance and particularly to introduced species, due to their small size. Island groups, such as New Zealand and Hawaii, have undergone substantial extinctions and losses of habitat. Since the 1950s several organisations and government agencies around the world have worked to restore islands to their original states; New Zealand has used them to hold natural populations of species that would otherwise be unable to survive in the wild. The principal components of island restoration are the removal of introduced species and the reintroduction of native species.
Lantana camara is a species of flowering plant in the verbena family (Verbenaceae), native to the American tropics. It is a very adaptable species, which can inhabit a wide variety of ecosystems; once it has been introduced into a habitat it spreads rapidly; between 45ºN and 45ºS and less than 1,400 metres in altitude.
The cane toad in Australia is regarded as an exemplary case of an invasive species. Australia's relative isolation prior to European colonisation and the Industrial Revolution, both of which dramatically increased traffic and import of novel species, allowed development of a complex, interdepending system of ecology, but one which provided no natural predators for many of the species subsequently introduced. The recent, sudden inundation of foreign species has led to severe breakdowns in Australian ecology, after overwhelming proliferation of a number of introduced species, for which the continent has no efficient natural predators or parasites, and which displace native species; in some cases, these species are physically destructive to habitat, as well. Cane toads have been very successful as an invasive species, having become established in more than 15 countries within the past 150 years. In the Environment Protection and Biodiversity Conservation Act 1999, the Australian government listed the impacts of the cane toad as a "key threatening process".
The Ascension scrub and grasslands ecoregion covers the dormant volcano, Ascension Island in the Atlantic Ocean. As well as shrubs and grasses wildlife on the island includes a range of unique flora and fauna. In particular the surrounding islets are important havens for many seabirds. However the seabird populations on Ascension Island itself have been severely affected by introduced species, especially cats, which were the subject of an eradication campaign between 2002 and 2006.
Feral goats are an invasive animal species in Australia. First arriving in the 18th century with European settlers, feral goat populations originated from escaped domestic individuals. Today, feral goats are found across Australia, where they cause economic and environmental damage through overgrazing and competition with livestock and native marsupials.
Red foxes pose a serious conservation problem in Australia. 2012 estimates indicate that there are more than 7.2 million red foxes, with a range extending throughout most of the continental mainland. The species became established in Australia through successive introductions, by settlers, beginning around the 1830s. Due to its rapid spread and ecological impact, it has been classified as one of the most damaging invasive species in Australia.
As with a number of other geographically isolated islands, Hawaii has problems with invasive species negatively affecting the natural biodiversity of the islands.
Feral cats are an invasive species in Australia. Because they are not native to Australia and were only introduced by European colonists as pets in the early 1800s, native Australian animals did not co-evolve with them. As of 2016, some 3.8 million domestic cats and up to 6.3 million feral cats continue to live in Australia.
Australia has a population of about 26 million while the Commonwealth Government estimating there are 640,000 recreational hunters in the country. There are around 6 million legally owned guns in Australia, ranging from airguns to single-shot, bolt-action, pump-action, lever-action or semi-automatic firearms.
Native to both South and Central America, Cane toads were introduced to Australia in the 1930s and have since become an invasive species and a threat to the continent's native predators and scavengers.
The Invasive Species Council is an Australian environmental non-governmental organisation founded in 2002 to provide a specialist policy and advocacy focus on reducing the threat of invasive species that threaten the environment.
The Froggatt Award is presented to people who have made a major contribution to protecting Australia's native plants and animals, ecosystems, and people from dangerous new invasive species.
The red imported fire ant is an invasive species in Australia originating from South America but imported to Australia, New Zealand, the United States of America and several Asian and Caribbean countries. Fire ants are listed by the International Union for Conservation of Nature (IUCN) as one of the world's most invasive species.