Common invasive species in the Adelaide Hills: olive, artichoke thistle, fennel and bamboo
A European rabbit (Oryctolagus cuniculus) in Tasmania
Invasive species are a serious threat to the native biodiversity of Australia and are an ongoing cost to Australian agriculture. Numerous species arrived with European colonisation of Australia and steadily since then.
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.
Causes
Both geologic and climatic events helped to make Australia's fauna unique. Australia was once part of the southern supercontinent Gondwana,
which also included South America, Africa, India and Antarctica.
Gondwana began to break up 140 million years ago (MYA); 50 MYA Australia
separated from Antarctica and was relatively isolated until the
collision of the Indo-Australian Plate with Asia in the Miocene era 5.3 MYA. As Australia drifted, it was isolated from evolutionary pressures in the rest of the world. Other examples of island isolation include Madagascar, New Zealand, Socotra, the Galapagos and Mauritius.
The placental mammals made their reappearance in Australia in the Pleistocene, as Australia continued to move closer to Indonesia,
both bats and rodents appearing reliably in the fossil record. The
geographic isolation of Australia created a sharp division between
Australian fauna and Asian fauna at the Wallace line.
Humans arrived in Australia between 65,000 and 80,000 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 & 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 4,600 and 5,400 years ago, long
after the first humans, spread rapidly across the continent and probably
contributed to the extinction of even more native species. 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. Recently citrus canker was introduced into Australia, and many Queensland citrus orchards have been burned to remove the disease. The fungus 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.
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 for domestic purposes (i.e. pets, recreational use – such as hunting – or beasts of burden) which have gone wild.
- Pests – animals which 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
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. Foxes 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. Camels and 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 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 and is considered a pest to livestock.
Invasive birds
Feral rock pigeons are common pests in public spaces in cities
Introduced birds considered pests include the common myna, the common starling, the spotted dove and rock pigeon (common pigeon).
Initially introduced to control locust plagues, 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). The bird has caused human health
concerns due to the spread of mites and disease and it has also been
known to force native birds and their eggs from their nests.
The rock pigeon in particular has acidic faeces and can damage human property, including historic stone buildings.
Control
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.
Invasive freshwater fish species
Invasive freshwater fish species in Australia include carp, brown trout, rainbow trout, redfin perch, mosquitofish (Gambusia spp), 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, 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.
Insects and other invertebrates
Fire ant
Problem insects include red imported fire ants (Solenopsis invicta), 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").
The elm leaf beetle (Pyrrhalta luteola), discovered in Victoria in 1989 devastates exotic elm trees, 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.
Control
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.
The 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.
The yellow crazy ant is currently quarantined to Christmas Island where it has had a significant environmental impact. The primary impact is the killing and displacing of crabs on the forest floor.
Invasive marine species
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.
Invasive plant species
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. A list of Weeds of National Significance (WONS) was created in 1999 and updated in 2012 and now has 32 taxa.
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.
Management of invasive species
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.
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. It has also led to much public concern and caution when considering the introduction of new biological controls.
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.
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 bush fly
number by 90%, as well increasing soil fertility and quality by
recycling the dung back into the soil.
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). 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.
World Trade Organisation and Australia's quarantine regulations
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 or bananas from the Philippines.
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.
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. 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.
