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Dr Trudi Ryan
Homeleigh Cottage
Wallaroo Rd
Hall ACT 2618
[email protected]
0417 210 643
October 10, 2003
Re: Inquiry into the regulation, control and management of invasive
species and the Environment Protection and Biodiversity
Conservation Amendment (Invasive Species) Bill 2002
Thank you for the opportunity to respond to the Inquiry into the regulation,
control and management of invasive species. Most of my comments relate to
my PhD research on the ecology and invasion impacts of the native invasive
plant, Sweet Pittosporum (Pittosporum undulatum) (Mullett 1999, 2001,
The views expressed in this submission are solely those of the author and do
not represent the views or policy of any associated organisation or agency.
Trudi Ryan
Terms of Reference 1: The regulation, control and management of
invasive species, being non-native flora and fauna that may threaten
This inquiry only considers non-native flora as invasive species yet a growing
number of native Australian plants are regarded as invasive species in natural
and semi-natural Australian ecosystems. My research on the ecology of a
native invasive plant species, Pittosporum undulatum, demonstrated that this
species exerted significant invasion impacts in a range of habitats both within
and beyond its natural range (Mullett 1999, 2001, 2002). These results
support the growing consensus in the weed literature, that invasive native
plants can be as ecologically destructive as invasive plants introduced from
outside Australia (Humphries et al. 1991; Groves 2001).
Invasion of natural ecosystems by native plant species is a conservation
problem experienced by all States and Territories of Australia. Over 100
native plants are now considered invasive in Victorian ecosystems and at least
50 native plants also function as environmental weeds in South Australia
(Groves 2001). Sixty-four native species, including 22 Western Australian
species, are considered invasive in natural Western Australian environments.
Such inter-regional invasions are likely to be on the increase. The incidence
of native plants as weeds was the subject of a symposium hosted by Monash
University in 2001 (see references for details).
Some native species can function as invasive plants in their natural,
indigenous habitats, if the ecological conditions that previously contained the
species have been modified. The tall native shrub, P. undulatum, is native to
the wet forests of south-eastern Australia and is a serious invader of dry
sclerophyll forest and other vegetation communities both within and beyond
its natural ecological range. This adaptable species has exploited changes in
natural disturbance regimes (principally the suppression of fire regimes) and
increased dispersal opportunities to spread from abundant garden plantings
into native vegetation communities, where it displaces indigenous plant
species and reduces habitat diversity.
1a) the nature and extent of the threat that invasive species pose to
the Australian environment and economy
Weed invasions cost Australian agriculture $3.3 billion p.a. in control and lost
production. The cost of weed invasion to Australia’s natural environments is
beyond calculation. Weed invasions are recognised as second only to
vegetation clearing as a cause of species decline. Invasive plants reduce
access to recreational activities, diminish the aesthetic values of natural areas
and homogenise the regional distinctiveness of natural ecosystems.
Pittosporum undulatum poses a very serious threat to the native plant
communities that it invades. Significant declines in plant species richness and
abundance has been recorded at sites throughout this species current
geographic range in south-eastern Australia (Mullett 1999, 2001, 2002).
Simplification of community composition, structure and function are principal
effects of invasion. Once set in train, the degradation of biodiversity values is
perpetuated at invaded sites as the rate and direction of community
succession moves towards a more simplified state. Habitat opportunities for
native fauna are also reduced with increasing weed invasion.
1b) The estimated cost of different responses to the environmental
issues associated with invasive species, including early eradication,
containment, damage mitigation and inaction
It is difficult to estimate the cost of early eradication versus containment
strategies. My data on the population structure and invasion impacts of P.
undulatum indicate that the cost of control increases with time since invasion.
The potential for eradication may also decrease with time since invasion.
Early eradication is the key to successful weed management. Inaction against
plant invasion will result in the loss of biodiversity.
1c) the adequacy and effectiveness of the current Commonwealth,
state and territory statutory and administrative arrangements for
the regulation and control of invasive species.
Current Commonwealth, state and territory statutory and administrative
arrangements are failing to address the threat posed by invasive species.
Greater political commitment to the principles of weed related policy and
legislation is required. For example, the invasion by P. undulatum into
habitats outside its natural range in Victoria was listed as a ‘potentially
threatening process’ in 1994 under Schedule 3 of the Victorian Flora and
Fauna Guarantee Act 1988. An Action Statement has not yet been developed
for this listing, despite the legislative requirement that this occurs as soon as
possible after the listing process.
1d) the effectiveness of Commonwealth-funded measures to control
invasive species
At the current rate of investment, most invasive plants are increasing both in
distribution and abundance. Volunteer groups conduct the majority of onground environmental weed control in Australia. Greater technical and
financial support needs to be supplied to volunteer groups if the onus of weed
management remains on the community.
1e) Whether the Environment Protection and Biodiversity
Conservation Amendment (Invasive Species) Bill 2002 could assist
in improving the current statutory and administrative arrangements
for the regulation, control and management of invasive species.
The Bill could improve the management of invasive species but it would need
to include native weeds in its definition of invasive species and expand its
focus to a broader range of introduced plants than those listed in the terms of
reference. The underlying causes of weed invasion will need to be addressed
in Threat Abatement Plans and adequate funding and support to address
these causes should be provided.
Cited References
Groves R.H. (2001) Can some Australian plants be invasive? Plant Protection
Quarterly 16, 114-17.
Humphries S.E., Groves R.H. & Mitchell D.S. (1991) Plant invasions of
Australian Ecosystems: a Status Review and Management Directions. Kowari
2, 1-134.
Mullett T.L. (1999) The Ecology of Pittosporum undulatum Vent
(Pittosporaceae), an Environmental Weed in south east Australia. PhD Thesis,
Deakin University, Victoria.
Mullett T.L. (2001) Effects of the native environmental weed, Pittosporum
undulatum Vent. (sweet pittosporum) on plant biodiversity. Plant Protection
Quarterly 16, 117-21.
Mullett T.L. (2002) The Biology of Australian Weeds 41. Pittosporum
undulatum Vent. Plant Protection Quarterly 17, 130-9.
See also:
Proceedings of a Symposium on Native Plants as Weeds published in Plant
Protection Quarterly (2001) Volume 16, Issue 3
Can some Australian plants be invasive? (R.H. Groves)
Effects of the native environmental weed Pittosporum undulatum Vent.
(sweet pittosporum) on plant biodiversity. (Trudi L. Mullett)
Transcontinental invasions of vascular plants in Australia, an example of
natives from south-west Western Australia weedy in Victoria. (J.P. Pigott)
Australian plants as weeds in Victoria. (G.W. Carr)
NGIA initiatives in environmental weed management. (Jolyon Burnett)
Native plants as environmental weeds on the Mornington Peninsula. (Scott
Biological control of weedy native plants in Australia. (Eligio Bruzzese and Ian
A challenge for our values: Australian plants as weeds. (Tim Low).