Ana səhifə

Advice to the Minister for the Environment, Heritage and the Arts from the Threatened Species Scientific Committee (the Committee) on Amendments to the List

Yüklə 0.55 Mb.
ölçüsü0.55 Mb.
  1   2   3   4   5

The Minister listed this as a key threatening process, effective from 8 January 2010

Advice to the Minister for the Environment, Heritage and the Arts from the Threatened Species Scientific Committee (the Committee) on Amendments to the List of Key Threatening Processes under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

  1. Name and description of the threatening process

1.1 Title of the process
Loss and degradation of native plant and animal habitat by invasion of escaped garden plants, including aquatic plants.
1.2 Name Changes
The original title of the nomination was ‘Loss and degradation of native plant and animal habitat by invasion of escaped garden plants’. The Committee changed the name of the nomination to ‘Loss and degradation of native plant and animal habitat by invasion of escaped garden plants, including aquatic plants’ to reflect that the threatening process is not restricted to the terrestrial environment.
1.3 Description of the process
The homogenisation of the global flora and fauna through the mass movement of species is creating one of the greatest environmental challenges facing the planet (Wilson, 1992). In natural ecosystems, invasive plants impact negatively on the biodiversity of many Australian

vegetation types ranging from tropical wetlands to arid riverine vegetation. Leigh and Briggs (1992) identified weed competition as the primary cause for the extinction of at least four native plant species, and estimated that another 57 species were threatened or would become so in the future through competition of weeds. These figures almost certainly underestimate the contemporary problem by a large margin.

The gardening industry is by far the largest importer of introduced plant species, being the

source for the introduction of 25 360 or 94% of non-native plant species into Australia (Virtue et al., 2004). Garden plant introductions are also the dominant source of new naturalised plants and weeds in Australia. Of the 2779 introduced plant species now known to be established in the Australian environment, 1831 (or 66%) are escaped garden plant species (Groves et al., 2005; Beeton et al., 2006). Furthermore, invasive garden plant species – both introduced and native species outside their natural range – are by far the largest source of environmental weeds (weeds which impact on natural biodiversity), comprising 72% of the 1765 listed environmental weeds (Groves et al., 2005).

Furthermore, it is anticipated that introduced garden plants will comprise an even greater portion of all naturalised species in the future (Groves et al., 2005). Of great concern is that many serious environmental weeds continue to be imported into Australia by the garden and nursery sector and, in the case of aquatic plants, the aquarium industry. In addition to this, an increasing number of Australian native plants are invading beyond their natural indigenous range, with their spread facilitated by the nursery and garden industry and enthusiastic gardeners (Blood, 2006).

Invasive garden plants can be defined as plants that are currently or were historically used in gardens, primarily for ornament or utility, which have escaped or threaten to invade natural and other areas (Randall, 2001; Blood, 2006). Whilst in most cases species categorised as invasive garden plants are those that were initially introduced for ornamental horticultural purposes, this is not always the case. For example, some environmental weeds such as Blackberry (Rubus fruticosus aggregate) and Radiata Pine (Pinus radiata), have been grown in gardens and may therefore be classified as invasive garden plants even though their introduction was originally for agricultural and plantation purposes, respectively (Randall and Kessal, 2004; Groves et al., 2005).

In terms of the general invasion process and their ultimate impact on native biodiversity, invasive garden plants are indistinguishable from other types of environmental weeds. Plant invasion is a continuous process, depicted in Figure 1 below, which comprises at least three stages:
1. An introduction stage commencing with the arrival of a ‘new’ species to a region.

2. A naturalisation stage whereby those introduced plant species are reproducing naturally without human intervention or cultivation.

3. An invasive stage where the naturalised plant species becomes widespread and/or abundant (and ultimately impacts adversely on native indigenous species).
Figure 1: The three stages in weed development (Barker et al., 2006)

Garden plants may escape the confines of a garden and enter native bushland via natural dispersal vectors such as wind, water, insects, birds and other animals, however, humans are by far the most effective and efficient vector of plants (Coutts-Smith and Downey, 2006; Randall, 2007). For example, humans facilitate the direct introduction of escaped garden plants by inappropriate dumping of garden waste and, in the case of aquatic garden plant escapees such as Salvinia (Salvinia molesta) and Cabomba (Cabomba caroliniana), emptying of aquariums and backyard ponds and deliberate planting to allow wild cultivation for the aquarium trade (Blood, 2006; DAFF and DEW, undated).
The likelihood of invasion success and the time required for a plant to become naturalised after introduction, or subsequently become invasive, is variable and depends, in part, on introduction effort or propagule pressure (Groves et al., 2005; Lockwood et al., 2005; Rejmanek et al., 2005).

Propagule pressure is a measure of the number of individuals released into a region to which they are not native. It incorporates estimates of the absolute number of individuals involved in any one release event (propagule size) and the number of discrete release events (propagule number). As the number of releases and/or the number of individuals released increases, propagule pressure also increases (Mulvaney, 2001; Lockwood et al., 2005). Propagule pressure, together with the ecological attributes or life history traits of the escaped garden plant itself and the condition of the receiving environment, are important factors for determining the strength and severity of this threatening process (Lockwood et al., 2005; Rejmanek et al., 2005).

In the context of invasive garden plants, propagule pressure largely reflects human preferences for particular non-native species, extent of commercial trade between countries and regions, and the effort that humans expend in importing, distributing and releasing large numbers of non-native and non-indigenous individuals (Sullivan et al., 2004; Lockwood et al., 2005). Figure 2 illustrates the garden plant invasion pathway, with arrows representing propagule flow by human vectors and, to a lesser extent, natural vectors.
Figure 2: The Garden Plant Invasion Pathway (Adapted from Glanznig, 2006)

The temporal nature of the threatening process results in a phenomenon whereby the past sale and distribution of garden plant species (which may or may not be currently available for sale) is responsible for the naturalisation and invasion of environmental weeds that is evident in the landscape today. The seriousness of the threat that invasive garden plants pose, given time, is demonstrated by fact that ten of the 20 Weeds of National Significance (WoNS) are weeds of horticultural origin and 16 in total have been cultivated for ornamental horticulture (Groves et al., 2005). Table 1 outlines these 16 WoNS, including their current availability for sale. Similarly, the negative ecological effects of potentially invasive garden plants currently available for sale may not be apparent for decades because, as yet, they have not been planted in large enough numbers, or over a long enough period, or in susceptible habitats, to have had an opportunity to realise their invasive potential (Mulvaney, 2001).

According to Groves et al. (2005) the ten most serious invasive garden plants being sold currently by Australian nurseries are Asparagus Fern (Asparagus scandens), Broom (Genista spp.), Fountain Grass (Pennisetum setaceum), Gazania (Gazania linearis), Glory Lily (Gloriosa superba), Hybrid Mother of Millions (Bryophyllum daigremontianum x B. tubiflorum = Bryophyllum daigremontianum x B. delagoense cv. ‘Houghtonii’), Japanese Honeysuckle (Lonicera japonica), Pepper tree (Schinus areira), Periwinkle (Vinca major) and Sweet Pittosporum (Pittosporum undulatum).

Table 1: Invasive Garden Plants that are now recognised as Weeds of National Significance (Adapted from Glanznig et al., 2004)

Scientific name

Common name

Naturalised where?1

Potential to Naturalise2

Available for sale?

Alternanthera philoxeroides

Alligator Weed

Qld3, NSW, ACT, Vic, WA, NT

SA, Tas


Annona glabra

Pond Apple



Yes – NSW

Asparagus asparagoides

Bridal Creeper

Vic, SA, NSW, Tas, WA

Qld, ACT

Yes – NSW**

Cabomba caroliniana


Vic, NSW, Qld, NT, ACT

WA, SA, Tas, ACT

Yes – SA*

Chrysanthemoides monilifera

subsp. monilifera

subsp. rotundata

Bone Seed

Bitou Bush

Vic, SA, NSW, Qld, Tas, WA

Vic, SA, NSW, Qld


Cryptostegia grandiflora

Rubber Vine

Qld, NT, WA



Lantana camara


NSW, Qld, NT, WA, Vic, SA

Vic, SA, Tas

Yes – NT*, WA, Vic

Mimosa pigra


NT, Qld

WA, Qld


Nassella trichotoma

Serrated tussock

Vic, ACT, NSW, Tas

WA, SA, Qld


Parkinsonia aculeata


SA, NSW, Qld, NT, WA

Vic, SA


Prosopis spp.


Qld, NSW, WA


Rubus fruticosus aggregate


Vic, SA, NSW, Qld, Tas, WA, ACT


Salix spp.
Salix alba

Salix alba subsp. vitellina
Salix cinerea
Salix purpurea
Salix × sepulcralis var. chrysocoma


Vic, ACT
NSW, Vic

Vic, ACT


SA, Tas

Yes –


Salvinia molesta


Vic, NSW, Qld, NT, WA, ACT



Tamarix aphylla

Athel Pine

Qld, NSW, SA, NT, WA

Yes – WA

Ulex europaeus


Vic, SA, NSW, Tas, WA, ACT, Qld


1 The sources for reporting which states and territories invasive garden plants have naturalised are Randall 2001 and

Groves et al 2003.

2 Potential to naturalise information taken from and

3 Alligator Weed is actively targetted for extermination in Queensland.

* Refers to those species in Aussie Plant Finder (2002) as available for sale that were subsequently prohibited for

sale in the given state.

** Regional declarations prohibit the sale of bridal creeper in a number of regions in NSW.

1.4 Threats to native species
According to Groves et al. (2005), invasive garden plants represent 28 (57%) of the 49 naturalised non-native plant species that impact on rare or threatened native plant species. Groves et al. (2005) also outline 13 milestones on the road to extinction. Milestone 8 is recognised as “excessive competition from introduced species”. This hierarchy of milestones acknowledges that weeds are not necessarily the primary cause of species decline. In many cases, land clearing resulting in habitat destruction, degradation and fragmentation has caused the initial reduction in species numbers and abundance. Environmental weeds then become a threat when invading remaining habitats, especially where these are already fragmented or degraded (Beeton et al., 2006).
Table 2, adapted from the 2006 State of the Environment Report (Beeton et al., 2006), lists native species that are believed to be under threat from various introduced plants. The primary source does not identify which of the weeds implicated can be considered escaped garden plants but other sources (Randall and Kessal, 2004; Groves et al., 2005) indicate that the weeds identified in Table 2 are recognised as naturalised invasive and potentially invasive garden plants.
The list of native species included in Table 2 that are adversely impacted by invasive garden plants is by no means exhaustive. For instance, a report by Coutts-Smith and Downey (2006) documented that invasive plants were a major threat impacting on 419 threatened species in New South Wales. The main threat was attributed to 127 invasive plants, 82 of which were identified as plants that had escaped from parks, gardens and ornamental collections. The five weed species most commonly implicated as threatening biodiversity in New South Wales were Lantana, Bitou Bush, Blackberry, Kikuyu (Pennisetum clandestinum) and Scotch Broom (Cytisus scoparius), all of which are escaped garden plants. The study concluded that, collectively, garden escapees threaten at least 190 native species (and maybe as many as 300 native species) in New South Wales alone.
Table 2: Examples of native species believed to be under threat from invasive garden plants

(Adapted from Beeton et al., 2006)

State and Territory

Threatened species

Invasive garden plants*


Tussock Skink (Pseudemoia

Gorse (Ulex europaeus)


Zieria Prostrata
(Zieria prostrata)2
Austral Toad-flax
(Thesium australe)2

Bitou Bush (Chrysanthemoides monilifera subsp. rotundata)


Cumberland Plain Woodland2
Pink Pimelea (Pimelea spicata)2

Bridal Creeper (Asparagus asparagoides)


Hairy Quandong (Elaeocarpus

Lantana (Lantana camara)

NSW and Victoria

Mountain Pygmy Possum
(Burramys parvus)2

English Broom (Cytisus scoparius subsp. scoparius)
Blackberry (Rubus fruticosus aggregate)


Eltham Copper Butterfly
(Paralucia pyrodiscus lucida)1

Cape Broom (Genista monspessulana)
Radiata Pine (Pinus radiata)
Quaking Grass (Briza maxima)


Common White Spider Orchid
(Caladenia argocalla)2

Topped Lavender (Lavandula stoechas)
Soursobs (Oxalis pescaprae)
St John's Wort (Hypericum perforatum)
Gorse (Ulex europaeus)
Hawthorn (Crataegus monogyna)
Watsonia (Watsonia meriana var
bulbillifera )

Qld and NSW

Richmond Birdwing
Butterfly (Troides

Dutchman's Pipe (Aristolochia elegans)


Aponogeton Queenslandicus

Para Grass (Brachiaria mutica)


Jabiru (Ephippiorhynchus
asiaticus australiensis)1

Para Grass (Brachiaria mutica)


Brolga Park Zieria (Zieria bifida previously Zieria sp. “Brolga Park”)2

Lantana (Lantana camara)


Proserpine Rock Wallaby (Petrogale persephone)2

Pink Periwinkle (Catharanthus roseus)
Rubbervine (Cryptostegia grandiflora)



Watsonia (Watsonia meriana var
Blackberry (Rubus fruticosus aggregate)
Gladioli (Gladiolus undulatus)


Yellow Chat (Alligator Rivers) (Epthianura crocea tunneyi)2

Mimosa (Mimosa pigra)

1 Listed as threatened only under state/territory legislation.

2 Listed as threatened under both state/territory and national legislation.

* Naturalised invasive and potentially invasive garden plants (Randall and Kessal, 2004; Groves et al., 2005).
The Committee considers that escaped garden plants have had, and are continuing to have, adverse impacts on a number of threatened native species and ecological communities throughout Australia. For the purposes of this listing advice, the affected species examined in more detail are Troides richmondia (Richmond Birdwing Butterfly), Pimelea spicata (a shrub), Pterostylis arenicola (Sandhill Greenhood Orchid) and Lasiopetalum pterocarpum (Wing-fruited Lasiopetalum).
Additionally, the ‘Cumberland Plains Woodlands’, ‘Blue Gum High Forest of the Sydney Basin Bioregion’ and ‘Littoral Rainforest and Coastal Vine Thickets of Eastern Australia’ are examined as examples of ecological communities listed as threatened under the EPBC Act that are adversely impacted by this threatening process.
The impact of escaped garden plants is evident across the three levels of biological diversity: genetic diversity, species diversity and ecosystem diversity. Many escaped garden plants that become environmental weeds are capable of causing an impact at one or more of these levels, although the degree of impact is rarely quantitatively determined (Adair and Groves, 1998). Escaped garden plants can have an adverse impact through genetic effects, introduction of diseases, competition for resources, prevention of recruitment, alteration of ecosystem processes and changes to the abundance of indigenous fauna (Burgman and Lindenmayer, 1998; Csurches and Edwards, 1998).
1.4.1 Genetic effects

In instances where escaped garden plants become environmental weeds and cause a decline in the number of genetically distinct sub-populations that make up a native species, it is reasonable to conclude that an associated reduction in the genetic diversity of the affected species is likely to result. As intra-specific genetic variation is the basis for continuing evolution and also the ecological versatility of a species, a decline in genetic variation reduces a species’ resilience and adaptability and increases a species’ vulnerability in the face of change (Adair and Groves, 1998; Burgman and Lindenmayer, 1998).

The invasion of escaped garden plants may also affect the genetic diversity of native species through cross breeding or hybridisation, whereby foreign genes are introduced into local plant populations (Blood, 2001). Escaped garden plants can hybridise with closely related endemic native plant species, leading to reduced genetic fitness and hence viability of endemic native plant populations. For example, Acacia baileyana (Cootamundra Wattle), a native species that has become an environmental weed outside its natural range through cultivation as a garden plant, is capable of hybridising with indigenous species including Acacia dealbata (Silver Wattle) and Acacia pubescens (Downy Wattle) (Brunskill, 2002; NGINA 2009). Similarly, in the Dandenong Ranges and South Gippsland in Victoria, another native garden plant which is considered a weed outside its natural range, Pittosporum undulatum (Sweet Pittosporum), is hybridising with the indigenous Pittosporum bicolor (Banyalla), threatening the survival of the local gene pool (Gleadow and Ashton, 1981; Parks Victoria, 2001).
1.4.2 Introduction of diseases

The introduction of exotic garden plants often results in the introduction of pathogens (fungi, nematodes, bacteria and viruses) that are associated with these plants in their natural range (ILDA, 2009). In their natural habitats and hosts, pathogens do little harm. In a novel environment, however, these pathogens can cause disease which adversely impacts on native vegetation (Pain, 2004).

The best known example of such a pathogen in Australia is Phytophthora cinnamomi. P. cinnamomi is a soil-borne microorganism which grows on the surface of plant roots and invades the cells of susceptible host plants, feeding on their root and basal stem tissue until the host plant is weakened or killed by a reduction or cessation in the movement of water and nutrients within the plant (WA CALM, 2003). While there has been some controversy concerning the origin of P. cinnamomi in Australia, it is believed that it is possibly of Asian origin and that it almost certainly entered Western Australia for the first time on soil around the roots of cultivated plants, shortly after European settlement (WA CALM, 2003; Cahill et al., 2008). Since this time it is speculated that there must have been innumerable introductions at many points of entry around Australia in association with the introduction of exotic garden plants (WA CALM, 2003; Pain, 2004).
Like terrestrial plants, aquarium and other aquatic plants carrying pathogens in their roots can adversely affect native plant and animal species, with fish being particularly susceptible to infection from aquatic plant-borne parasites (QLD EPA, 2008). Aquatic plants like Salvinia can also indirectly facilitate the spread of pathogens as they provide breeding habitat for other pest species such as disease-carrying mosquitoes (CRC AWM, 2003).
The introduction of pathogens caused by the mass movement of garden plants also creates opportunities for different species of pathogens to interact, pathogens which would not meet under natural conditions. This interaction is problematic as it may result in the evolution of new and potentially dangerous diseases (Pain, 2004).
1.4.3 Competition for resources

Competition between species is inevitable when more than one species occupy the same niche and have similar requirements for a limited resource (Cadotte, 2007). Escaped garden plants are known to compete with native plants for limited resources such as moisture, nutrients, sunlight, pollinators and space (Csurches and Edwards, 1998; Blood, 2001; Brunskill, 2002).

Many escaped garden plants in Australia become invasive because they are introduced in areas that do not contain their natural pests and predators which, under normal circumstances, would play a significant regulatory role. In the absence of natural pests and predators, growth of escaped garden plants can become extremely vigorous such that a competitive advantage over native vegetation is gained. Blue Trumpet Vine (Thunbergia grandiflora) is an example of a garden escapee, spread primarily via the ornamental plant trade, that gained a competitive advantage in north Queensland owing to the absence of damaging insects and pathogens (Csurches and Edwards, 1998; QPIF, 2008; AWC, undated).
The competitive advantage that many escaped garden plants possess is also a function of the ecological attributes or life history traits of the escaped garden plant itself. For example, Bitou Bush has a much greater reproductive output than the native Acacia longifolia (Sydney Golden Wattle), owing to the competitive advantage of Bitou Bush at the seedling stage. The competitive advantage of Bitou Bush is primarily derived from the species’ comparatively greater root development, allowing better access to moisture, and its greater leaf area which results in a greater rate of photosynthesis. Both of these ecological characteristics enable Bitou Bush to outgrow and out-compete the Sydney Golden Wattle (Weiss and Noble, 1984).
1.4.4 Prevention of recruitment

Growth of invasive garden plants can be sufficiently vigorous to reduce or prevent the establishment of native plant species (Csurches and Edwards, 1998). For example, the establishment of Sweet Pittosporum results in the development of a low tree canopy of almost rainforest density, which intercepts light to the extent that only about ten percent of full daylight reaches the understorey (Gleadow and Ashton, 1981). The intensity of the shade cast by dense growth of Sweet Pittosporum may inhibit native plant seed germination; in dry sclerophyll forests east of Melbourne, for example, it resulted in a 90 percent decline in native plant species and in some cases caused the complete loss of the forest understorey (Gleadow and Ashton, 1981; Csurches and Edwards, 1998; Mullett, 2001).

1.4.5 Alteration of ecosystem processes

Invasive garden plants are also capable of altering various ecosystem processes such as geomorphological processes, hydrological cycles, nutrient dynamics and disturbance regimes (Csurches and Edwards, 1998). Alterations to ecosystem processes can potentially influence many if not all species within a community (Vranjic et al., 2000).

For example, with regard to geomorphological processes, the invasion of the exotic Marram Grass (Ammophila arenaria) is believed to have resulted in changes to the topography of sand dunes in Australia (Csurches and Edwards, 1998; Hilton et al., 2006). Additionally, the establishment of invasive garden plants, such as Willows, can indirectly increase soil erosion by shading out ground plants which would normally hold the soil together (Blood, 2001). Similarly, the presence of Lippia (Phyla canescens), a major invasive garden plant species in the Murray- Darling Basin, can also result in increased soil instability as Lippia’s root system is less effective than that of native grasses in binding cracking clay soils (Groves et al., 2005).
Escaped garden plants may also influence hydrology. For example, the invasion of watercourses in central Australia by Tamarix spp. (Tamarisks) is likely to have resulted in a change in the hydrology of the Finke River and a lowering of the water table (Csurches and Edwards, 1998). Tamarisks are unable to actively regulate their transpiration such that, in dry conditions, they may desiccate watercourses in order to meet their moisture requirements (Griffin et al., 1989; Groves et al., 2005).

The nutrient dynamics of soil and litter substrates may also be altered by invasive garden plants. Cootamundra Wattle, for example, fixes nitrogen in the soil, thereby inhibiting the germination of many native plants (WBMB, undated). Bitou Bush, another example, can alter soil and litter properties substantially, and these changes negatively impact on the germination and seedling growth of indigenous plants such as Acacia sophorae (Coastal Wattle) (Vranjic et al., 2000). Similarly, Sweet Pittosporum produces leaf litter that is considerably different in terms of nutrient content to that of native eucalypts. Gleadow and Ashton (1981) found that, under laboratory conditions, the leaf litter of Sweet Pittosporum, which contains greater levels of calcium and magnesium, significantly inhibited, and may be allelopathic to, seed germination of several native eucalypt species. Invasive aquatic plants, such as Cord Grasses, are also capable of altering the nutrient dynamic of waterways as well as pre-existing pH, salinity and oxygen levels, all of which impact on native aquatic life (Hedge and Kriwoken, 2000).

Disturbance regimes, such as fire regimes, can also be altered by the invasion of escaped garden plants. Invasive garden plants can change intrinsic fuel properties (plant tissue moisture content and chemical composition) and extrinsic fuel properties (fuel load, continuity and packing ratio), which can in turn affect fire behaviour and, ultimately, alter fire regime characteristics such as frequency, intensity, extent, type, and seasonality (Brooks et al., 2004). Characteristics of many invasive garden plants that enable them to fuel very intense fires include abundant, highly flammable volatile leaf oils, very fine fuels (abundant small leaves and branches) and the formation of very dense thickets. Invasive garden plants often produce fuel loads that greatly exceed natural fuel loads, resulting in fires so intense that the soil is sterilised and all plants and soil-stored seed are destroyed. Escaped garden plants such as Blackberry, Gladioli (Gladiolus undulatus) and Watsonia (Watsonia sp.), for example, contribute to accumulated fuel loads and therefore increase the risk of fire (Stack and English, 2003). If the regime changes subsequently promote the dominance of the invaders, then a positive feedback loop or an invasive plant–fire regime cycle can be established (Brooks et al., 2004).
1.4.6 Changes to abundance of indigenous fauna

Escaped garden plants that become invasive can both directly and indirectly change the abundance of indigenous fauna. Fauna such as the Richmond Birdwing Butterfly and Petrogale persephone (Proserpine Rock Wallaby) are directly impacted by escaped garden plants, Dutchman’s Pipe (Aristolochia elegans) and Pink Periwinkle (Catharanthus roseus), respectively, both of which are attractive as a food source and yet toxic to them when consumed (Watts and Vidler, 2006).

Indirectly, escaped garden plants impact indigenous fauna by altering the availability of suitable habitat, including food and shelter, and by creating habitats that harbour other pest species that can, in turn, have a detrimental affect. In the Northern Territory, for example, thickets of Mimosa (Mimosa pigra) were found to be unsuitable for Anseranas semipalmata (Magpie Goose), which relies on native sedges displaced by Mimosa for nesting and food, and to have lower overall bird and lizard abundances compared to native vegetation (Groves et al. 2005). Similarly, Blackberry is capable of out-competing native vegetation that Burramys parvus (Mountain Pygmy Possum) depends on for food and shelter, and it also provides food and shelter for introduced pests such as dogs and foxes which are known to prey on the possum (Mansergh et al., 1991; TSN, 2005).

1.5 Listing status under State and Territory legislation
The following are listed as potentially threatening processes under the Victorian Flora and Fauna Guarantee Act 1988:

  • ‘Invasion of native vegetation by Blackberry Rubus fruticosus L. agg’

  • ‘Invasion of native vegetation by ‘environmental weeds’’

  • ‘Introduction and spread of Spartina to Victorian estuarine environments’

  • ‘Spread of Pittosporum undulatum in areas outside its natural distribution’

New South Wales
The following are listed as key threatening processes under the NSW Threatened Species Conservation Act 1995:

  • ‘Invasion and establishment of exotic vines and scramblers’

  • ‘Invasion and establishment of Scotch Broom’

  • ‘Invasion of native plant communities by bitou bush & boneseed’

  • ‘Invasion of native plant communities by exotic perennial grasses’

  • ‘Invasion, establishment and spread of Lantana camara

In addition, the NSW Scientific Committee has made a preliminary determination to list the ‘Invasion and establishment of escaped exotic garden plants’ as a key threatening process.

Many weeds that originated as garden plants are also declared as noxious or prohibited under various state/territory legislation.

  1. How judged by the Committee in relation to the EPBC Act criteria

Section 188(4) of the EPBC Act states:
A threatening process is eligible to be treated as a key threatening process if:

  1. it could cause a native species or an ecological community to become eligible for listing in any category, other than conservation dependent; or

  2. it could cause a listed threatened species or a listed threatened ecological community to become eligible to be listed in another category representing a higher degree of endangerment; or

  3. it adversely affects 2 or more listed threatened species (other than conservation dependent species) or 2 or more listed threatened ecological communities.

A. Could the threatening process cause a native species or an ecological community to become eligible for listing as Extinct, Extinct in the Wild, Critically Endangered, Endangered or Vulnerable?
There are a number of species not listed as threatened under the EPBC Act that are likely to be negatively impacted by escaped garden plants. However, there are currently insufficient quantitative data available to enable assessment of the impacts on most of these species against this criterion. There is however, evidence that the threatening process could cause Troides richmondia (Richmond Birdwing Butterfly) to become eligible for listing as threatened under the EPBC Act.

Richmond Birdwing Butterfly
This species’ eligibility for listing under the EPBC Act can be assessed using relevant criteria set out in the Environment Protection and Biodiversity Conservation Regulations 2000. The species would be considered to be vulnerable if it met any one of the criteria set out in the regulations. The following criterion is relevant in the case of Richmond Birdwing Butterfly: ‘It has undergone, is suspected to have undergone or is likely to undergo in the immediate future, a substantial reduction in numbers’.
The Richmond Birdwing Butterfly occurs only in subtropical northern New South Wales and south-east Queensland. The species was once reportedly very common in Brisbane and its natural range extended from Maryborough and Gympie in Queensland to Grafton in New South Wales (Gardening Australia, 2003; Vidler, 2004; Sands, 2008). Significant contraction in the species’ distribution has occurred over the last century in response to extensive clearing of lowland rainforest for forestry and farming (Sands, 2008). Continuing declines in abundance and distribution of the butterfly and its native food plants have occurred over the last 20 years and it is estimated that less than two-thirds of the original population’s range remains (Sands, 2008). The Committee considers that the past decline in the species’ population size would be commensurate with this range contraction.
Escaped garden plants turned invasive weeds, including Morning Glory (Ipomoea spp.), Madeira Vine (Anredera cordifolia) and, in particular, Dutchman’s Pipe (Aristolochia elegans) have been identified as significant threats that have contributed to the Richmond Birdwing Butterfly’s decline over the last couple of decades (Sands, 2008). Dutchman’s Pipe has been particularly problematic and its impact is two-fold. Firstly, it can have an indirect impact on the Richmond Birdwing Butterfly by competing with and displacing what remains of the species’ native food plant vines, Pararistolochia praevenosa (Birdwing Butterfly Vine) and Pararistolochia laheyana (Mountain Aristolochia) (Sands, 2008). Secondly, in the absence of native food plants, butterflies are attracted to laying their eggs on the leaves of the related, but introduced, Dutchman’s Pipe. Leaves of Dutchman’s Pipe contain toxins that poison and kill the larvae of the Richmond Birdwing Butterfly when they hatch and commence feeding (Gardening Australia, 2003; Vidler, 2004; Biosecurity Queensland, 2007; Sands, 2008; Qld EPA, 2009). Dead larvae of the species have been observed everywhere the weed occurs, including in national parks (Sands, 2008).
Despite significant recovery effort to date which has involved nurseries and school groups undertaking cultivation and planting of the native food plant throughout Brisbane gardens, the Dutchman’s Pipe continues to threaten the survival of the butterfly and it is considered that eventual eradication of the Dutchman’s Pipe may not be feasible in some extensive habitats. Furthermore, it is anticipated that the threat posed by the Dutchman’s Pipe will continue as future climate change is expected to favour the competitiveness and expand the range of this and other invasive weeds (Sands, 2008). The Committee therefore considers that the Richmond Birdwing Butterfly is likely to undergo a substantial reduction in numbers in the immediate future.
Summary of assessment: The Richmond Birdwing Butterfly was once reportedly very common in Brisbane and its natural range extended from Maryborough and Gympie in Queensland to Grafton in New South Wales. However, the species has been adversely affected by invasive garden plants, the impact of which is exacerbated in the context of past clearing and a highly fragmented habitat.
The Committee considers that the species has undergone a substantial reduction in numbers consistent with a substantial reduction in range. The species’ distribution is dictated by the distribution of its native food plant and, in future, the latter will be largely dictated by the expansion of various invasive garden plants, including the Dutchman’s Pipe. The survival of the butterflies that remain is also jeopardised by virtue of the fact that the leaves of the Dutchman’s Pipe are poisonous to feeding Richmond Birdwing Butterfly larvae.
Further, the decline in population size and geographic distribution may continue if the threat of invasive garden plants continues. The level of this threat is not yet quantified but it is anticipated that future climate change will increase the competitive advantage of escaped garden plants such as the Dutchman’s Pipe. The Committee considers that the Richmond Birdwing Butterfly is likely to undergo a substantial reduction in numbers in the immediate future.
The Committee judges that this threatening process could cause the Richmond Birdwing Butterfly to become eligible for listing under the EPBC Act.
Conclusion for Criterion A: The Committee considers that the threatening process is eligible under this criterion as the process could cause the Richmond Birdwing Butterfly to become eligible for listing as threatened under the EPBC Act.

B. Could the threatening process cause a listed threatened species or a listed threatened ecological community to become eligible to be listed in another category representing a higher degree of endangerment?

Escaped garden plants, along with other threatening processes, could cause the Cumberland Plain Woodlands ecological community, currently listed as endangered, to become eligible for listing as critically endangered under the EPBC Act.

The Cumberland Plain Woodlands ecological community supports a range of escaped garden plant species including:

  • African Olive (Olea europaea subsp. cuspidata);

  • Branched Centaury (Centaurium tenuiflorum)

  • Bridal Creeper (Asparagus asparagoides);

  • Cat’s Ear (Hypochaeris radicata);

  • Glandular Willow-herb (Epilobium ciliatum);

  • Moth Vine (Araujia sericifera);

  • Pimpernel (Anagallis arvensis);

  • Spear Thistle (Cirsium vulgare);

  • Square Cicendia (Cicendia quadrangularis);

  • Yellow Wood Sorrel (Oxalis corniculata)

(NSW Scientific Committee, 2008b; DEWHA 2009b).

All of these escaped garden plant species compete for space and resources and, in doing so, may displace native species and contribute to a reduction in native plant and animal biodiversity.

African Olive and Bridal Creeper have been identified as particularly significant weeds as they are highly competitive and appear able to suppress native understorey species (Benson, 1992; Tozer, 2003; TSSC, 2009). Bridal Creeper and Moth Vine are among a suite of exotic vines and scramblers that are listed as a threatening process in NSW which are also considered a specific threat to the ecological community (NSW Scientific Committee, 2006; TSSC, 2009).
African Olive has established as an aggressive environmental weed since its introduction into Australia in the mid-19th century as an ornamental and hedging plant and as a rootstock for the European Olive (Olea europaea subsp. europaea). It has an ability to permanently change the structure of the ecological community through dense mid-canopy formation and, like other weeds such as Bridal Creeper, can suppress native plant species in the understorey (Benson, 1992; Cuneo and Leishman, 2006; TSSC, 2009). The establishment of African Olive within a patch of the ecological community can also significantly alter the types of fauna using the patch (NSW DECC, 2007; TSSC, 2009).
Morris and Wood (2001) found that 14 of 57 identified species (11% of the total) that germinated from the soil seed bank of the Cumberland Plain Woodlands ecological community were exotic species. Similarly, Hill and French (2003) found that 11 of 68 species represented in the soil seed bank of the ecological community were weeds. However, the identification and origin of the weed species was not revealed by the authors of either study. Notwithstanding this, Hill and French (2003) reported that two of the ten species found to be unique to the soil seed-bank (not present in standing vegetation) were Glandular Willow-herb (Epilobium ciliatum) and Square Cicendia (Cicendia quadrangularis), both of which are invasive garden plants. The presence of Glandular Willow-herb and Square Cicendia seeds in the soil profile can reduce the seed-bank of native species and their regeneration capacity. The fact that these garden plant species are unique to the soil seed-bank suggests that their invasive potential is yet to be fully realised and these species may have an increasingly detrimental impact in the future (Hill and French, 2003). Furthermore, Hill and French (2003) reported that Yellow Wood Sorrel (Oxalis corniculata), another escaped garden plant, was the most abundant of 11 temperature-tolerant species to germinate from all soil samples collected from the ecological community.

The following criteria are relevant in determining the Cumberland Plain Woodland’s eligibility for listing as critically endangered: ‘Small geographic distribution coupled with demonstrable threat’ and ‘Reduction in community integrity’.

Small geographic distribution coupled with demonstrable threat

The Cumberland Plain Woodlands were formerly extensive and scattered across the entire Cumberland Plain, an area of about 2800 km2 (NSW Scientific Committee, 2008b). As remnants of the ecological community continue to be scattered across the entire Cumberland Plain, this value approximates the extent of occurrence for the ecological community. Based on its extent of occurrence, the Cumberland Plain Woodlands has a limited geographic distribution, i.e. it lies well within the range of 1000 to 10 000 km2 (TSSC, 2009).

The ecological community’s area of occupancy has markedly contracted from about 130 900 ha to approximately 12 300 ha (Tozer, 2003; NSW Scientific Committee and Simpson, 2008) and there is a strong possibility of further decline. The area of occupancy for the Cumberland Plain Woodlands is, therefore, indicative of a restricted geographic distribution (TSSC, 2009).

Data on patch sizes for the ecological community indicates that about 87% of woodland remnants are under 10 hectares in size, with about 72% of remnants falling within the size range of 0.5 to 5 hectares. Large remnants of 100 ha or more in area are comparatively rare, accounting for less than 1% of the number of remnants. The distribution of patch size classes indicates that the present geographic distribution of the Cumberland Plain Woodlands is highly fragmented and can be considered to be very restricted (TSSC, 2009).

In addition to the threat of clearing for urban development and the subsequent fragmentation of the ecological community that ensues, the Cumberland Plain Woodlands ecological community is seriously threatened by invasion of escaped garden plants, particularly African Olive which has been mapped across about 985 hectares of the Cumberland Plains Woodlands (Cuneo et al., 2009). Given current urban expansion and infrastructure development plans, the threat of escaped garden plants will continue to intensify, rather than diminish (TSSC, 2009).
The Committee considers that the ecological community has a very restricted geographic distribution, based on the fragmentation of remnants into very small patch sizes, coupled with demonstrable ongoing threats that could cause it to be lost in the immediate future. Therefore, the ecological community is eligible for listing as critically endangered under this criterion (TSSC, 2009).
Reduction in community integrity

A number of the threats and disturbances that contribute to a reduction in the integrity of the Cumberland Plain Woodlands ecological community are common to temperate grassy ecosystems across south-eastern Australia. The major difference is that the entire distribution of this ecological community is within or in close proximity to the greater Sydney metropolitan area. This juxtaposition with an urban environment makes the Cumberland Plain Woodlands particularly susceptible to anthropogenic threats. Where the ecological community has not been outright cleared and irrecoverably lost, the integrity of remnants has declined over time in response to a number of threats including the invasion of escaped garden plants (TSSC, 2009).

The Cumberland Plain Woodlands ecological community is subject to extensive invasion by several weed species which originated as garden plants, most notably African Olive. African Olive can have transformative impacts upon remnants of the ecological community - it has the ability to permanently change ecosystem structure by forming a dense mid-canopy formation, blocking out the understorey plant species and preventing the regeneration of tree canopy species (Cuneo and Leishman, 2006; TSSC, 2009). Cuneo et al. (2009) used satellite imagery to determine that African Olive has infested 8.5% of the ecological community in the south of the Cumberland Plain. Fragmentation of the ecological community increases the threat of African Olive as the increased edge effects of remnants allows increased dispersal of weed propagules into remnants (Hobbs and Huenneke 1992).
Escaped garden plant species with the potential to aggressively invade the understorey, such as Bridal Creeper, are also present at some sites. Where Bridal Creeper is extensive, the tuber mat limits establishment sites for native ground layer species, whilst the climbing shoots can smother native vegetation into the small tree canopy. Effective control for these escaped garden plant species is likely to be problematic and difficult. Consequently, these garden plant species will continue to be a key factor contributing to the reduction in the integrity of many patches of the ecological community into the foreseeable future (TSSC, 2009).
The Committee considers that the change in integrity experienced by the ecological community, as indicated by invasion of escaped garden plants, is very severe. The nature of the changes in integrity of the ecological community are such that the regeneration of many patches is unlikely to occur within the immediate future, even with positive human intervention. Therefore, the ecological community is eligible for listing as critically endangered under this criterion (TSSC, 2009).
Conclusion for Criterion B: The Committee considers that the threatening process is eligible under this criterion as the process could cause the Cumberland Plain Woodlands to become eligible for listing as critically endangered, a category which represents a higher degree of endangerment, under the EPBC Act.

C. Does the threatening process adversely affect two or more listed threatened species (other than conservation dependent species) or two or more listed threatened ecological communities?
As discussed under ‘Threats to Native Species’ there are a number of species being impacted upon by this threatening process. The following species, listed as threatened under the EPBC Act, are examples that demonstrate the adverse impacts of escaped garden plants on threatened Australian native species. These species are being affected by escaped garden plants primarily through competition and habitat degradation.

    • Pimelea spicata (a shrub)

    • Pterostylis arenicola (Sandhill Greenhood Orchid)

    • Lasiopetalum pterocarpum (Wing-fruited Lasiopetalum)

Additionally, the ‘Blue Gum High Forest of the Sydney Basin Bioregion’ and ‘Littoral Rainforest and Coastal Vine Thickets of Eastern Australia’ are examples of ecological communities listed as threatened under the EPBC Act that are adversely impacted by this threatening process.

Pimelea spicata

Pimelea spicata is endemic to New South Wales and is currently listed as endangered under the EPBC Act. P. spicata is a small shrub growing to about 50 cm that bears pink-white flowers from September to May. It reproduces mainly from seed but also possesses a thick tap root that enables re-sprouting after fire and other disturbances (Groves et al., 2005). Although once widespread in southeastern New South Wales, the species is now restricted to approximately 30 populations and has a relatively scattered distribution occurring in two disjunct areas - the Cumberland Plain Woodland (itself a nationally threatened ecological community) and Illawarra (Matarczyk et al., 2002; Vidler, 2004). The species’ current distribution is largely a result of habitat fragmentation caused by clearing for rural and urban development (NSW DEC, 2004; NSW NPWS, 2004c).
Invasive weeds that are able to out-compete P. spicata for resources have severely degraded the species’ habitat, thereby threatening the viability of remnant P. spicata populations (NSW DEC, 2004; Watts and Vidler, 2006). Indeed, according to Matarczyk et al. (2002), if current rates of habitat loss and weed invasion continue unchecked, the species is at risk of disappearing from the wild within the next 10-20 years. The major weeds adversely impacting P. spicata include Bridal Creeper (Asparagus asparagoides), Bitou Bush, Blackberry, St John’s Wort (Hypericum perforatum), Kikuyu, Lantana, African Olive (Olea africana subsp. africana) and Broad-leaved Privet (Ligustrum lucidum) (Vidler, 2004; Watts and Vidler, 2006). The invasion of these weeds, most of which are escaped garden plants, is likely to detrimentally affect P. spicata by reducing the reproductive capacity of adult plants and their ability to resprout following disturbance, and by inhibiting seedling recruitment (NSW DEC, 2004).
P. spicata is particularly susceptible to displacement by environmental weeds due to its herb-like habit, and is especially vulnerable to competition from weeds that can form a dense ground cover such as Kikuyu and Bridal Creeper. Kikuyu is known to compete with P. spicata at the majority of sites and is likely to cause the local extinction of the species at a number of sites in the absence of effective control measures (NSW DEC, 2004). For example, Kikuyu along with Bitou Bush and Lantana are invading coastal populations and having a major impact on the recruitment of P. spicata from the seedbank (DEWHA, 2009d).
The adverse impact of Bridal Creeper on the native shrub is particularly evident at one of the largest P. spicata populations near Camden which comprises about one-quarter of all remaining individuals. At this site, Bridal Creeper is known to co-occur at varying densities with about 60 per cent of P. spicata adults (Groves et al., 2005). Bridal Creeper is capable of competing with P. spicata both above and below ground (Vidler, 2004). Preliminary evidence suggests that the latter form of competition is relatively more intense as the presence of Bridal Creeper roots, irrespective of shoots, can limit the germination of P. spicata. This has negative implications for the early life history stages of P. spicata (Groves et al., 2005).
While the removal of Bridal Creeper may lead to localised increases in P. spicata populations, the species’ habitat will always be predisposed to further weed invasion because the vegetation type in which P. spicata occurs is highly fragmented (Groves et al., 2005).
  1   2   3   4   5

Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2016
rəhbərliyinə müraciət