The CRC for Australian Weed Management submitted that
early eradication of invasive plants saves 83 native species (plants and animals)
from extinction for each $1 million spent. This compares with only seven
species saved per $1 million spent on the herbicidal and mechanical control of
weeds once they are widespread, or one species saved per $1 million spent on maintaining
environmental flows in rivers.
Clearly, the cost-benefit ratio of action outweighs inaction. For example, Bitou
bush (Chrysanthemoides monilifera ssp.
rotundata), a species from South Africa, dominates coastal vegetation in
eastern Australia and impacts on biodiversity as well as diminishing public
access to beaches. The Bureau of Rural Sciences argued that a preliminary
economic analysis of the cost-effectiveness of a program for the control of Bitou
bush estimated that the cost of loss and damage is 20 times greater than the
cost of control.
The cost of managing invasive species varies and is
difficult to quantify. The South
Australian Animal and Plant Control Commission noted the need to examine the
cost-effectiveness of various responses to pest management. The Committee considers below the
response options of eradication, containment, damage mitigation and inaction.
The Committee heard evidence that the early eradication
of pest incursions provides significant cost-benefit ratios and provides a
higher chance of success than other responses:
Costs are likely to be minimal
in terms of applied resources and there is a much higher chance of success....
Value for money is probably highest at this stage, particularly if the invasive
species has not established where it has impacted on the environment. 
In its submission to the inquiry the Bureau of Rural
Sciences noted that:
eradication is an ideal response but is technically extremely
difficult, if not impossible, for most invasive species.
However, the benefits of early eradication were
supported by the Weeds CRC which noted that the current eradication campaign
against branched broomrape is estimated to have a benefit/cost ratio of 7.9
with an internal rate of return of 22%.
The WWF argued that prevention and early control are
the least costly and most effective approach to managing invasive species. The
Prime Minister’s Science, Engineering and Innovation Council (PMSEIC) report, Sustaining our Natural Systems and
Biodiversity, concluded that limiting the spread of pests, weeds and
imported diseases is one of four areas of investment above all others that is
likely to return greatest impact in heading off the diminishing value of
Australia’s natural systems and biodiversity.
The table below illustrates the effectiveness of a $1
million investment over a range of intervention strategies.
Table 4.1 - Costs and benefits of intervention strategies
No. species secured/$1m
broadscale clearing of high ecological value communities in Queensland
broadscale clearing of communities in the MDB that have high multiple
ecosystem service value
ecological communities which have fallen below 10% back to 10% of their
original area, in the 5 IBRA regions that have <30% native vegetation
native vegetation in all IBRA sub-regions that have fallen below 10% back to
10% of their original area
the National Reserve System to achieve comprehensiveness targets
the health of rivers that are least disturbed
river health to rivers in poor condition
environmental flows are at least 15% of sustainable water yield.
the spread of Phytophthora
new outbreaks of naturalised plant species with weedy potential
control of weeds of national significance
and herbicidal control of weeds (Mimosa example)
control of vertebrate pests
control of feral predators (Earth Sanctuary example)
revegetation to prevent salinity from further affecting remnant vegetation
grazing of 10% of all arid and semi-arid grazing lands
grazing for conservation in threatened grasslands in South East Australia
fire management regimes in native vegetation which promote a diversity of
The Queensland Government submitted that:
Experience in Queensland
has shown that prevention and early eradication are significantly more cost
effective responses than containment/damage mitigation actions for invasive
species.... An essential component of any system must also be an early warning
monitoring and surveillance program. To date such programs have not been widely
included as part of the response to incursions. At the same time strategic
control programs have been carried out on established pests when it considered
that this would result in significant reductions in pest impacts. Awareness and
extension activities are very cost effective.
The Committee took evidence from the Quarantine and
Export Advisory Council which noted that the recent incursion in Queensland of
the exotic red imported fire ant required a commitment of $140 million to an
eradication program and the papaya fruit fly detection and eradication program
run over four years cost approximately $34 million (see case study on fire ants in
Chapter 5). The Queensland Government informed the Committee that:
A Benefit Cost Analysis was undertaken by ABARE in 2001 into the
proposed eradication program. This analysis found that the cost to the
community if the fire ant was not controlled would be $8.9 billion over a
30-year period. The major costs were from loss of property values, cost of
household repairs and treatment and the cost to agriculture. This study
provided a BCR of 25:1 based on a $124m, five-year program that is well above
the limit where eradication is considered worthwhile. However, this analysis is
very conservative - it did not include the costs from the loss of environmental
and lifestyle values that this ant would cause.
Achieving early eradication requires a number of
conditions, these include: proper planning, commitment to complete the process,
putting the entire population of the target species at risk, removing them
faster than they reproduce and preventing reinvasion. Although the up front
costs of early eradication programs may be significant, the cost of weed and
pest control activities after the pest is widespread and established are
usually significantly more costly and time consuming.
The Bureau of Rural Sciences argued that six criteria
that must be met for an eradication to be successful. These are:
The rate of removal must exceed the rate of
increase at all population densities
Immigration must be zero or the probability of
reinvasion should be considered
Target species must be detectable at low
All reproductive individuals must be at risk
Discounted cost-benefit analysis must favour
eradication over control; economics should favour eradication
There must be a suitable socio-political
environment; adequate resources must be committed to see the eradication
project through to completion; and clear lines of authority must be
The following is an example of a successful eradication
program which illustrates a number of the criteria outlined above.
Case study: Eradication
of the Black-striped mussel
The fouling mussel, Mytilopsis sp., colloquially known
as the black-striped mussel, are small marine bivalve mollusc originating from
Central and South America. They have spread to several countries in the
Indo-Pacific region, and are considered a serious pest because of their ability
to rapidly establish large populations and cause significant environmental and
economic impacts This mussel is a fast growing filter-feeder that clings to
boats and pilings and has the capacity to jam water intake pipes. It is closely
related to the freshwater zebra mussel that costs the United States $100 million a year to control in the Great Lakes alone.
The black-striped mussel was discovered in three loched marinas within
The Port of Darwin - Cullen Bay Marina, Tipperary Waters Marina and the Frances Mooring Basin (also known as the ‘duck pond’) in March
1999 at densities up to 23,650 m-2 during a opportunistic port survey. It had
reached those densities in less than six months. The mussels were probably
introduced into Darwin on the hull of a commercial or recreational vessel travelling from
infected ports in other parts of the world.
On discovery of the invasion the Northern Territory government reacted rapidly to quarantine the infected
area within three days of being informed by CSIRO of the presence of the black
striped mussel in a Darwin marina. The mussel was seen as a major environmental and economic
threat to the Northern Australian coastline (between Sydney to Perth) and also a major threat to the local $40 million pa
pearl oyster fishery.
The response management committee coordinated the
on-ground containment and treatment actions (involving over 300 personnel). The
main actions undertaken included the tracking and treatment of vessels that had
left infected sites, the treatment of three sites and almost three hundred
vessels in the Darwin area and the initiation of a public awareness program to
meet local and national needs. Commonwealth agencies led by Agriculture
Fisheries and Forestry - Australia (AFFA) established a national working group
on 6 April 1999 to coordinate national action to prevent the spread of the
mussel to other States. Other agencies involved included Environment Australia
(EA), Commonwealth Scientific and Industrial Research Organisation’s
(CSIRO) Centre for Research on Introduced Marine Pests
(CRIMP), the Australian Fisheries Management Authority (AFMA), the Australian
Quarantine and Inspection Service (AQIS), the Australian Maritime Safety
Authority (AMSA), the Australian Customs Service (ACS), the Australian
Government Solicitor (AGS) and the Department of Defence (Navy). A local
scientific sub-committee comprising representatives from CSIRO CRIMP, NT Museum
and Art Gallery, DPIF and the Northern Territory University developed national
protocols to detect and treat the Black Striped Mussel at the Darwin sites and
on vectors considered to be at risk.
Between 31 March and 19 April 1999, chlorine (calcium and sodium hypochlorite) and
copper sulphate were added to the marina waters at a cost of over $2 million in
materials alone. Both treatments killed mussels but the copper sulphate proved
more effective. On 23 April 1999, 100% of the exotic Black Striped Mussels were deemed
successfully eradicated and , all three marinas were re-opened for normal use.
Procedures were established for continued monitoring to detect possible new
infestations. No further infestations have been detected to date.
response to the Black Striped Mussel outbreak
September 1998 Divers from CSIRO
CRIMP and the NT Museum & Art Gallery surveyed Darwin Harbour and marinas, including Cullen Bay Marina,
(as part of the Port
of Darwin baseline survey) and did not detect any
Black Striped Mussels (BSM).
27 March 1999 CSIRO
divers conducted the second component of the baseline survey and detected
massive infestations of BSM in Cullen Bay Marina.
29 March 1999 NT
Museum & Art Gallery alerted NT Department of Primary Industry and
Fisheries (DPIF) of BSM detection. The Minister and Chief Executive Officer of
DPIF were b
30 March 1999 Follow-up
dive surveys were coordinated by DPIF to determine the extent of the outbreak
outside Cullen Bay Marina A special meeting of the NT Cabinet to pass
regulatory amendments, approved the establishment of the Taskforce and the
expenditure of funds.
31 March 1999 NT
Cabinet and Executive Councils convened and legislative changes were approved.
A second BSM outbreak was found at Tipperary Waters Estate Marina. Six vessels
were contained within Tipperary waters. An emergency management committee was convened, response teams
were established, an information campaign commenced (including telephone
hotline, Internet site, public meetings), and marina locks were dosed with
sodium hypochlorite to create a sterile plug. One hundred and forty seven
vessels were contained within Cullen Bay Marina.
1 April 1999 A
vessel originally from Cullen Bay Marina moored in Frances Bay Mooring Basin was found to be carrying BSM. 70 vessels
were contained within Frances
Bay. An interstate alert was issued to owners of
vessels from Cullen Bay Marina to check vessels and not scrape hulls. The NT
Government quarantined the three infected marina sites to prevent further
spread of BSM, using a combination of the powers in the NT Fisheries Act
1988 and the Commonwealth Quarantine Act 1908.
2 April 1999 Four
vessels from Cullen Bay Marina moored in Sadgroves Creek were found to have BSM
and were removed from the water. Dive teams checked potential contamination
sites around Darwin
Harbour. A list of potentially contaminated vessels
that had left the marinas was developed by AQIS with the support of Australian
Fisheries Management Authority.
3 April 1999 Two
vessels from Cullen Bay Marina lifted at Spot On Marine were found to have BSM
and were removed from the water. Another contaminated vessel located at Frances Bay Mooring Basin was also removed from the water. Trial of
copper sulphate treatment commenced in Tipperary Waters Marina Estate.
4 April 1999 Chlorine
treatment of Cullen Bay Marina. Further copper sulphate treatment of Tipperary
Waters Marina Estate was undertaken. A vessel tracking database was established
and 420 vessels were identified as “at risk” of contamination (either those
still in the marinas or those which had left since the infection period).
Treatment of internal systems of vessels was trialled.
5 April 1999 Further
chlorine treatment of Cullen Bay Marina. Fish species killed during treatment
of the marinas were identified by the NT Museum. No further sign of BSM
infestation were found outside the three marinas.
6 April 1999 Further
chlorine treatment of Cullen Bay Marina. The National BSM Taskforce was
established led by Agriculture, Fisheries and Forestry - Australia. Copper sulphate was found to have a 100%
kill rate of mussels in Tipperary Waters Marina Estate. Four boats were slipped
and found to be infested with BSM.
7 April 1999 Copper
sulphate treatment of Cullen
Bay. Vessel cleaning protocols were released.
Scientific sub-committee of the National BSM Taskforce met to develop National
Protocols for treatment of vessels and anchorages between Fremantle and Sydney potentially infected with the BSM. Chlorine
treatment of Frances Bay Marina. Second public meeting at Cullen Bay.
8 April 1999 Copper
sulphate added to Frances
Bay. Gove Harbour was declared clear of BSM. NT DPIF staff
commenced checking the internal systems of Cullen Bay Marina vessels with
9 April 1999 Further
chlorine treatment of Cullen Bay Marina after heavy rain during previous 24
12 April 1999 Some
cleaned vessels were allowed to leave Cullen Bay Marina after a check of
monitoring areas in the marina revealed no live mussels.
15 April 1999 A
recently dead mussel found on a yacht from Cullen Bay Marina when lifted at
16 April 1999 Surviving
mussels were detected on vessels leaving Cullen Bay Marina. Both Cullen Bay and Tipperary Waters marinas were again
closed and quarantined. Intensive re-surveying and re-sampling commenced in
Cullen Bay Marina. National Protocols formally released.
17-19 April 1999 Intensive sampling of Cullen Bay Marina revealed two
live mussels, followed by two recently dead mussels in amongst hundreds of
thousands of dead mussels. Copper sulphate was added at specific sites in
Cullen Bay Marina.
20 April 1999 Cullen
Bay Marina reopened at high tide for limited access in and out of the marina.
Clearance dives were conducted in Tipperary Waters Marina Estate.
22 April 1999 Clearance
dives were conducted in Frances Bay Mooring Basin.
23 April 1999 Quarantine
conditions were lifted from Cullen Bay,
Frances Bay and Tipperary Waters marinas and all
were re-opened for normal use. Monitoring and sampling surveys continued.
29 April 1999 National
BSM Taskforce ceased operation.
8 May 1999 21 day “all
clear” issued for all three marinas. Precautionary vessel checking and
treatment arrangements remained in place.
May 1999 The Aquatic
Pest Management Program was established to monitor the impacts of BSM response
activities and oversee a continuing program of pest surveillance and control in
July 1999 The
National Taskforce for the Prevention and Management of Marine Pest Incursions
was established to examine improvements to all aspects of introduced marine
pest management. The Taskforce’s report was delivered to Government Ministers
on 23 December 1999.
Measures to effectively halt or minimise the spread of
invasive species can involve either keeping species within a fixed area
(containment) or keeping species out of an area (exclusion). Responses range
from physical barriers (e.g. fences or high security facilities) to chemical
barriers (e.g. poison baited buffer lines) through to virtual containment lines
(e.g. mapped containment areas). The cost of these activities is often greater
than prevention and it is likely that these actions will be integrated with
damage mitigation for many species. The Tasmanian Weed Society argued:
Containment costs can range from minimal expenditure associated
with early eradication extending to on-going high levels of cost associated
with restricting an established invasive to a particular area as eradication is
not considered possible or is considered too difficult or expensive. The latter
reason is flawed, as containment is very expensive when applied over a long
period. Additional expenses are incurred where containment provisions impact on
business enterprises in the containment area and restrict movement of people
and products. Environmental costs are higher as the invasive species will
continue to impact on the environment to a greater or lesser extent depending
on mitigation actions in the containment area. However, for many invasive
species present in Australia
this will be the most likely option for management.
As an example of the complexities of containment and
the difficult in achieving successful outcomes the CSIRO submitted:
Attempts to confine spiralling whitefly to the northern tip of Cape
York Peninsula proved ineffective. There were no serious attempts
to combine containment with eradication and the infestation, which soon spread
south to Cairns and beyond, is now
too widespread to contemplate eradication. In retrospect, there was little
point in bothering with a containment policy for this pest in the absence of
any clearly defined commitment to fund an eradication program.
The following case study provides an example of the
difficulty of containment with a view to eradicating established weed species.
Case study: Containment
of Branched Broomrape - Orobanche ramosa
Branched Broomrape (Orobanche ramosa) is a parasitic
weed of broad leaf crops and is found throughout many parts of Europe,
Central Asia, South Africa, North and Central America.
Broomrapes are root parasites that extract all their nutrient requirements from
their host plants. They have no leaves or chlorophyll and do not
photosynthesise. The weed is only detectable during a short flowering period
and is underground for the remainder of the life cycle. Infestations have been
masked by grazing and other factors, which would limit the detection of the
flower stalks and seed heads. Broomrape species infest 16 million hectares
world wide, which is 1.2% of the world’s arable land. They affect 51% of the
world’s sunflower crops, 35% of the world's faba bean crops, and 45% of the
world’s lentil. It can directly reduce yields up to 40% in some crops.
The potential impact of broomrape in Australia is very serious in terms of both production losses
and threats to export markets. The main industries at risk are oilseeds, field
peas, vegetables, lupins and vetch, and in particular, the seed industry for
Branched Broomrape was first detected in Australia in 1992 near Bow Hill South Australia. Until 1997, South Australian officials have conducted
an ongoing management program. In October 1998 South Australian authorities
detected a further spread to over 160 ha. The Commonwealth Chief Plant
Protection Officer (CPPO) was notified in February 1999 of the new
Further surveys were carried out and a national
Orobanche ramosa consultative committee, chaired by the CPPO was convened to
assess the infestation in March 1999. In early 1999 the infestation area had
grown to over 100 ha and the Australian Weed Committee (AWC) and Standing Committee
on Agriculture and Resource Management (SCARM) agreed on a national eradication
program. A decision to eradicate was delayed until the distribution of the weed
was clearly determined. A strategy to conduct a national awareness program,
delimiting surveys in South
research on the host range of the weed was developed.
Surveys in the springs of 1999 and 2000 established
that the known infestation was contained within an area of about 70 x 70 km,
northeast of Murray Bridge in south Australia. Infested Paddocks in 130 properties total about
11,000 ha. A national survey and awareness campaign has not revealed the
presence of branched broomrape elsewhere in Australia.
Unlike other weeds, broomrape species are spread by
millions of minute spore-like seeds and, except for a few weeks in the
flowering season, grow underground. The weed is spread mainly by soil
contamination through cultivation machinery and livestock. Its control requires
a similar strategy to the control of a disease epidemic, that is, isolation and
sterilisation of infested sites.
In South Australia the SA Government committed to a program of
fumigation to eradicate Branched Broomrape and to compensate the landowners who
make their living from the land hit by infestations. The fumigation and
incentive program for the eradication of Branched Broomrape will cost $7.6
million over four years.
The management of established pests generally involves reducing
the impact from the species (damage mitigation). In Queensland
it is estimated that these activities make up 30% of the programs funded by the
Department of Natural Resources and Mines and Local Government (AEC 2002). Control
activities include; chemical, mechanical or physical control, biological
control or habitat modification depending on the species. The Committee heard
that European foxes, feral cats and pigs, lantana and parkinsonia are all managed
to some level. The Tasmanian Weed
This course of action is one of the most difficult to employ as
by the nature of choosing this management option it is understood the invasive
species cannot be fully checked. Often not been feasible to eradicate from a
site or keep from reinvading without ongoing management input. It requires the
development of adequate means of control and a rationale to determine where
efforts should be focused. In many instances expensive biological control
programs are required to manage the impacts of weeds that fall into this
category. Localised efforts at damage mitigation by manual, herbicide and other
integrated techniques are similarly costly and cannot be applied on a large
scale by individual landholders or governments. A targeted approach based on a
strategic focus on the assets at risk is the most effective way of applying
The Bureau of Rural Sciences also noted the complexity
of a damage mitigation strategy in the management of invasives.
Damage mitigation through sustained control is a more complex
strategy than eradication or containment. Optimal management depends on knowing
when and where to intervene with optimal levels of control, and this depends on
a good understanding of the relationships between vertebrate pest densities and
resource conditions. The benefits need to be predicted or measured to optimise
The following case study illustrates the use of
biological control as a method of damage mitigation once an invasive species is
established and eradication and other forms of control are no longer a viable
Case study: Biological control
of bridal creeper
Bridal creeper, Asparagus
asparagoides, is an environmental weed that was introduced from South Africa into Australia in the middle of the 19th century as an
Bridal creeper is now a major weed and has become naturalised in many
temperate Australian ecosystems, ranging from wet and dry sclerophyll forests
to riparian and coastal vegetation systems. Its climbing vegetation smothers
native plants and it forms a thick mat of underground tubers which impedes the
root growth of other plants and often prevents seedling establishment. In many
instances it forms dense monocultures, and is regarded as a very serious threat
to biodiversity. Bridal creeper is regarded as one of the worst weeds in Australia because of its invasiveness, potential for
spread, and economic and environmental impacts and has been declared a weed of
national significance (WONS). Mr Peter Mirtschin from Venom Supplies in South Australia told the Committee that:
weed is now at epidemic proportions in southern Australia. In South Australia it abounds on the West Coast,
Eyre Peninsula, Yorke Peninsula, Adelaide Hills, Barossa valley, the southeast
and parts of the Riverland ... The weed is the dominant understorey plant in many
areas. Not only does it smother and replace low native plants but large trees
also succumb to its advance (see pictures on Kangaroo Island and Waikerie above).
Creeper threatens to cover all of southern Australia in the next 15 years.
Once invasive plants are established and widespread, the most
cost-effective control method is biological control using insects or plant
diseases introduced from the country of origin of the weed. Biological controls
deliver high cost-benefit ratios, are sustainable in the long-term and have
very few undesirable non-target effects. Biological control programs are
long-term, typically requiring funding for 5 to 10 years as well as expensive
Three biological control agents of bridal creeper have been released in
Australia: the leafhopper Zygina sp. in 1999, the rust fungus Puccinia myrsiphylli in 2000 and the leaf beetle Crioceris sp. in 2002.
A national redistribution program established in 2002, with the
financial assistance from the Natural Heritage Trust, has fast tracked the
release and spread of the leafhopper and rust fungus across the entire range of
bridal creeper infestations.
The bridal creeper leafhopper has been released at more than 700 sites
throughout southern Australia since 1999. The adult insect is white, 2-3
mm long and lives on the underside of bridal creeper leaves. Both the adult and
juvenile stages feed on the leaves of the weed, causing them to turn white and,
in severe cases, fall off. The plant will continue to grow but with much less
vigour. Continual damage over several years will reduce new tuber production,
making it less competitive.
The bridal creeper rust fungus was released in 2000 and more than 700
releases have been made across Australia. The rust fungus attacks leaves and stems,
reducing the amount of green plant material.
The bridal creeper leaf beetle (Crioceris
sp.) was first released in 2002 in Western Australia. The grubs of the beetle can cause major
damage to bridal creeper by stripping the shoots and leaves that enable the
plant to climb. Stopping it climbing will stop it fruiting and spreading to new
areas. Nursery sites of the leaf beetle are being established and monitored in
order to support future redistribution efforts.
In June 2004 CSIRO Entomology announced it had received funding from
the Natural Heritage Trust to support the continued delivery of biological
control agents in collaboration with community groups and land managers.
The effectiveness of biological control
Reports in 2003 of natural spread of the rust fungus of up to 1km from
release sites after one year are positive. The rust was seen to cause severe
defoliation of plants in the middle of the weed's growing season. This was
particularly apparent in Western Australia, New South Wales and Kangaroo Island in South Australia.
While the leafhopper has readily established at most release sites,
their performance is variable. In many places they simply establish and
populations stay in numbers too low to make any impact on bridal creeper. At
other sites they perform extremely well, spreading considerable distances and
causing early defoliation of bridal creeper.
It will take many years for the biocontrol agents to reduce the density of
bridal creeper due to the huge reserves stored underground in tubers, however,
it remains a cost-effective method of control.
Evidence received by the Committee strongly supported
the use of biocontrol methods to address invasive species. The Animal and Plant Control
Biological control remains one of the few
options for controlling invasive species over large areas. However these
programs are expensive and time consuming due in part to legislative and
consultation requirements. Support for biological control should be reaffirmed
and negotiations between Commonwealth and states should focus on simplifying
these processes to minimise the costs.
McFadyen, CEO of the Weeds CRC, told the Committee that:
The problem with biocontrol is that it needs long-term resources
and national support and that is what it is not getting. Again, I think there
needs to be some national support for biocontrol. To re-emphasise this, we are
saying that coordinated weed control, if it comes in early, can make a real
difference. It is important that we do something. We have made good progress on
some issues but we do need long-term national resources for those points.
Essentially, we are saying that it is a saving of national money.
Another method of control that is being developed for
damage mitigation is gene manipulation. The funding and support mechanisms for
the development of control methods using gene manipulation requires are similar
to the development of biological control agents as it can take a significant
period of time from inception to release of this technology. Contact with the
Gene Technology Regulator is required regarding regulations that may cover more
advanced stages of the project to ensure that there are no adverse impacts. Gene
manipulation technology is controversial and legal, logistical, environmental
and community barriers to release must be addressed prior to the release of the
Case study: Daughterless Carp -
Control through Gene Manipulation
Carpio), usually referred to as European
Carp, are native to Central Asia. They were introduced
to China, Japan
and Italy in
ancient times, and were first introduced into Australian waterways over 100
years ago. Since the 1960s they have bred particularly fast and now make up
more than 90 per cent of the total fish population in some Murray-Darling
Carp significantly degrade
waterways by causing increases in water turbidity and water nutrient levels. They
also damage the riverine habitat, uprooting aquatic plants and competing with
the native fish for food and habitat. River conditions that have
reduced native fish numbers also
favour carp. Carp prefer slow running waters and river pools, and are most
common in the highly regulated waters of the Murray River
and Murrumbidgee River.
A variety of methods have been
tried for controlling Carp.
fishing has the potential to significantly reduce carp numbers. In some parts
of South Australia targeted
fishing has reduced carp from 80% to less than 40% of the biomass.
number of community groups have reportedly been successful in removing carp
from wetlands and preventing re-entery by screening inlet channels
have been investigating the use of a virus known as spring viremia since the
1970s when it attacked farmed carp in Europe. However, it is not an option at
this stage because introducing such a virus may affect native fish and Australia's
have been successfully eradicated from lakes using the chemical poison rotene. However,
the use of poison in quantities large enough to affect carp is likely to have
significant impact on native plants and animals.
While some of these methods can
be effective in eliminating carp from enclosed water or in reducing their
numbers they are unlikely to provide a permanent solution. A more promising
avenue for control is the daughterless carp technology being developed by the
CSIRO, with support from the Murray Darling Basin Commission.
Daughterless Carp Technology
Daughterless carp technology involves
manipulating the genes of carp to produce an inheritable 'daughterless' carp.
Despite breeding normally, with each succeeding generation fewer and fewer
females will be produced in the wild population as this biological control
method restricts all offspring to males. It is predicted that this technology
will significantly reduce carp numbers in the Murray-Darling
Basin within 20-30 years of
The daughterless gene consists of
a promoter that activates the daughterless gene to express only in females.
During its brief period of activation, the daughterless gene inhibits
production of the key enzyme required for the fish to develop as a female - as
a result the fish defaults to a male. The genetic sequence used to produce
daughterless carp is found in the carp itself. This is species-specific
technology and native fish will not be affected by the technology.
This technology is still in a
developmental stage. For it to be effective it must be ecologically safe,
socially acceptable, economically affordable and cost effective. Research into
these factors must be conducted before any consideration can be given to
releasing 'daughterless' carp. A final decision on the release of carp that
carry the 'daughterless' gene will not be made until 2009.
manipulation technology opens a new avenue for controlling invasive species and
it is likely that a similar approach could be effective in combating other
Several factors influence the decision to adopt an
approach of inaction in relation to an invasive species. These include the
burden placed on landowners if a species is declared, the impact of a pest, the
geographic distribution of the pest, and whether the short-term management cost
is greater than longer-term cost if the species does spread. Inaction on a pest
may also be a valid response if no cost effective method of control is
available, although this may also lead to funds being set aside for research.
As the Queensland Government argued, however:
In many cases, inaction is not an option, public sentiment will
require at least extension material and research to improve management.
The cost of inaction is often felt in the longer term
when management costs and negative environmental effect maybe significantly higher. Failure to act can lead to a
situation where control, management, and damage mitigation are no longer
possible and the community has to suffer the effects of the invasion in the
longer term. The Tasmanian Weed Society submitted:
Short term costs of inaction are practically nil and this is
often an attractive option for jurisdictions that have limited budgets, or fail
to understand the implications of invasive species. Mid-term costs of inaction
are moderate where the invasive incident gradually impacts on production,
trade, aesthetics, and environment. The long term costs of inaction can be
immense and translate to the most expensive response to an invasive incident ...
Our environmental and cultural heritage is at risk and being slowly and
insidiously changed through inaction.
Cane toads are an example of what can occur as a result
of a failure to address a pest species.
Cane toads, which are native to Central and South
America, were released in Queensland
in 1935. Within a brief period of time they became established pests. Cane
toads are primarily environmental pests not agricultural, and have significant
impact on biodiversity:
Cane toads are seen as a major threat to biodiversity, not only
because they voraciously out-compete some native species for food and consume
others, but also because their skin toxins are thought to kill carnivorous
predators which mistake them for local amphibians. Although the impact of cane
toads on native Australian species is perceived to be detrimental, most reports
so far are anecdotal, a fact recognised at the workshop [Biological Control of Cane Toads, held in February 2004] by a
number of ecologists. Gradually, however, more quantitative data on the impacts
of native species are becoming available to greatly assist in confirming the
Principal Research Scientist, Australian Animal Health Laboratory, CSIRO told
the Committee that:
To see the long-term impacts, you need long-term studies. ... If
you have short-term discontinuous studies over a long period of time, you are
not going to derive the data whereby you can say definitely over a long period
of time there is a significant impact or not. Short term, however, as my
colleagues have said, there are published data to show that the impact of the
cane toad is dramatic in a short-term time frame in all areas-culture as well
A failure, across all tiers of government, to commit
adequate resources to manage them and to invest in the development of an
effective control method has resulted in their spread across vast areas of Queensland,
the Northern Territory and New
South Wales. Their range now extends to Kakadu
National Park. It is estimated that
they are spreading at a rate of 27 kilometres per annum.
There is a dearth of research into both the impact of,
and measures to control, cane toads. Evidence indicates that they have been
placed in the 'too hard basket' by many decision makers.
The case study below demonstrates what the outcome can
be if a new species is released without being subjected to thorough risk
assessment prior to release and the consequence of inaction once a species is
identified as being invasive.
Case study - Cane Toads 
Cane toads were deliberately introduced to Australia from Hawaii in 1935 in an attempt to stop French’s Cane
Beetle and the Greyback Cane Beetle from destroying sugar cane crops in North Queensland. The Australian Bureau of Sugar Experimental
Stations made the release of 101 cane toads at Gordonvale in Queensland. The cane toad was unsuccessful in
controlling cane beetles.
In Australia, most cane toads are found in urban areas
and in areas with grassland or woodland. Average adult-sized cane toads are
10-15 cm long. They are a fecund species; females lay 8,000 to 35,000 eggs at a
time and usually breed twice a year. Cane toads need between 6 and 18 months to
reach sexual maturity and have a lifespan, in the wild, of about 5 years. About
0.5% of cane toads that hatch from eggs survive to reach sexual maturity and
Due to their adaptability and the fact that they have no known predator
in Australia, with the possible exception of keelback
snakes, cane toads have been able to become established across a vast area.
Their food and habitat requirements are easily met. Cane toads eat mainly
insects, but will eat any small creature that fits in their mouth, including
marine snails, native frogs, small snakes, and small mammals. Adult cane toads
can survive the loss of up to 50% of their body water, and in temperatures
ranging from 5 - 40C and they can tolerate salinity levels of up to 15%.
Cane toads are toxic in all stages of their life cycle. Australian
native fauna, such as freshwater crocodiles, goannas, tiger snakes, dingos and
western quolls have died from cane toad venom. In Australia, no humans have died from cane toad venom,
however, it may cause intense pain, temporary blindness or inflammation if it
is absorbed by humans.
The ecological impacts of cane toads have been hard to identify as the
research required to determine the impacts is long term and multidisciplinary. However, the significant impact of
cane toads on biodiversity is undisputed. While some birds have learnt to turn
them over and take out the intestinal contents without eating the toxic skin
and evidence indicates that goannas learn to avoid them after experiencing
non-lethal doses of cane toad venom, other native species, such as quolls, do
not seem to learn to avoid the cane toads.
Although no extensive environmental monitoring studies have been undertaken,
evidence indicates that there has been a decline in quoll, snake and native
frog numbers in areas where large numbers of cane toads are found. The acute
effects of cane toads on biodiversity, such as through the killing of
freshwater crocodiles and quolls, can be readily seen in areas where they have
more recently moved.
Despite the negative impact cane toad have on a number of species they
are not officially recognised as a threatening process in Australia, because not all States consider toads to be
a problem. Only animals that are of national significance are officially
recognised as threatening processes.
At present there is no national strategy to address cane toads and
there is no broad-scale control method that can be applied to the vast area
where cane toads have spread. Current control activities for cane toads are
mainly taking place through quarantine checks and public awareness campaigns.
In Queensland no funds are currently expended by state
agencies as current control methods and the wide distribution of cane toads
suggest that funds will not effectively deliver an outcome as the species has
already reached its extent in the state.
A solution to cane toads is proving elusive. A number
of options for controlling cane toads have been investigated, and the
Commonwealth Government has spent $5 million on studies of how to eradicate
cane toads. However, a successful
control method has yet to be identified. From 1987-1989 researchers at James Cook University investigated possible controls focusing on diseases
in Australia that could affect cane toads, unfortunately the
research was unsuccessful. From 1989-1994 research focused on the original
habitat of the cane toad, Venezuela, and looked at diseases in South America that had the potential for use in Australia. Researchers identified a potential virus, however,
the virus killed one species of Australian amphibian and was therefore ruled
Currently hope for a solution rests with the CSIRO. In 2001 CSIRO
researchers commenced a project to investigate the possibility of creating a
biological control from a native amphibian virus which can interrupt the
metamorphosis of the cane toad and disrupt development. It aims to develop a
biological control option which could be deployed across the range of the cane
toads. The goal is to identify and manipulate a critical toad gene to disrupt
development and prevent the tadpole from maturing and therefore reproducing.
The second goal is to develop a method for delivering the gene effectively to
the toads genetics, using a viral infection.
The CSIRO project is high-risk research, at the
frontiers of research knowledge. It is expected to take 10-years from inception
before results can be delivered.
Biological control agents can be the most effective
method for addressing an invasive species. However, their development requires
significant financial and time investments from involved parties. As has been
demonstrated by previous research into control methods for cane toads, viable
solutions have proved elusive. It is hoped that with the support of the
Commonwealth, State and Territory Governments the CSIRO will be able to
identify a solution.
On 26-27 February 2004, a workshop titled "Biological Control of
Cane Toads" was held in Queensland. It was sponsored by the Australian
Government Department of Environment and Heritage under the National Threat
Abatement Component of the Natural Heritage Trust. The purpose of the workshop
was to provide information to the Australian scientific community and public
interest groups about the current CSIRO biological control project and to
discuss key issues relating to the impact and control of cane toads. At the
meeting it was agreed that there was a need for cane toads to be controlled
through a combination of short-term, local, methods as well as long-term,
nation-wide methods. It was also recognised that an effective national strategy
is required and research into cane toads must be coordinated if cane toad
populations are to be controlled.
The general recommendations arising from the workshop were:
- establish a
national cane toad group to coordinate research;
- collate and
document all current knowledge on the short and long-term impacts of cane
- identify gaps in
impact knowledge and support further research;
- identify and implement
short-term control and damage mitigation measures;
- identify research
gaps in short and long-term control methods; and
- provide support
for research into short and long-term control measures.
Recognition of the need for action has resulted from
an increase in awareness of the threat posed by the continued spread of cane
toads, and their impact on biodiversity.
At the Natural Resource Management Ministerial Council
(NRMMC) meeting in April 2004 there was consensus on the need to address cane
toads and the NRMMC directed its Vertebrate Pests Committee to investigate
options for a national approach to eradicate them. The inaugural meeting of the
National Cane Toad Taskforce was held in Darwin on 21 and 22 November 2004. The taskforce will report to the Vertebrate Pest
The Minister for the Environment, Senator Campbell, also foreshadowed the development of a
national cane toad group to coordinate a drive against the pest and called on
the Western Australia Government to work with the Commonwealth Government to
halt the migration of cane toads into Western Australia. Senator Campbell advised that:
Australian Government will take all measures available to stop the cane toad
order to safeguard the state from the impacts of this menace.
Cane toads have been able to spread across Australia
as a result of policies of inaction. It has only recently been recognised that
the impacts of cane toads are too significant for them to continue to be
ignored. The cost of this delayed response will be considerable and a solution
is many years away from being realised. The Committee expresses its hope that a
solution to the cane toads can be identified and implemented.
In 2002 the Prime Minister's Science, Engineering and Innovation
Council identified invasive species as one of four areas in which addressing
the decline of Australia's
natural systems and biodiversity provided the greatest return on investment.
The Committee acknowledges that the cost of inaction is high and the most cost
effective measure for dealing with invasives is prevention. Those propositions
are axiomatic. Early intervention and the prospect of eradication depend upon
effective emergency response arrangements.
In theory, the Committee would wish to see total
eradication adopted as the national goal, while recognising that such a course
is not without pitfalls given evidence that some invasive species have actually
proven beneficial to the survival of some native species, and may take many decades to be
In conclusion, in discussion the cost of responding to
invasive species, the Committee believes that the environmental impacts of
invasive species are substantial, the challenges are immense and the need for
action is urgent.