Biodiversity Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Dr Jann Williams, RMIT University, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06749 3
Biodiversity Issues and Challenges (continued)
Exotic Species and Genetically Modified Organisms
This section reports on the following environmental indicators, which are defined in Saunders et al (1998).
| Environmental Indicator | |
|---|---|
| BD 3.1 | Rate of extension of exotic species into IBRA |
| BD 3.2 | Pest numbers |
| BD 4.1 | Distribution and abundance of genetically modified organisms (GMOs) |
| BD 19.1 | a | b | | Number of management plans for exotic/alien/genetically modified organisms |
| BD 19.2 | Number of research programs for exotic/alien/genetically modified organisms |
| BD 19.3 | Funding for research and control of exotic/alien/genetically modified organisms |
Alien or exotic species
Introduction
One of the objectives of the National Strategy for the Conservation of Australia's Biodiversity was to implement effective controls for at least one introduced mammal and at least three introduced plant species by the year 2000. The National Weeds Program and the National Feral Animal Control Program aim to provide a strategic framework for addressing such goals. The Commonwealth EPBC Act also includes provision for protecting Australia's environment from invasive species. However, as indicated below, the magnitude of the task is daunting.
Pest animal species [BD Indicator 3.1]
Australia's pest animals are species that cause severe damage to natural and agricultural systems (Olsen 1998). These pest animals are either domestic animals that have gone wild or those that were introduced for the control of pests or for recreation. Pest animals causing most public concern include the European Rabbit (Oryctolagus cuniculus), European Fox (Vulpes vulpes), cat (Felis catus), pig (Sus scrofa), goat (Capra hirus), donkey (Equus asinus), camel (Camelus dromedarius), Water Buffalo (Bubalus arnee), Mosquito Fish (Gambusia holbrooki), Northern Pacific Seastar (Asterias amurensis), European Carp (Cyprinus carpio) and Cane Toad (Bufo marinus). Pest animals may damage vegetation and soils, foul water or compete with native animals for habitat and food.
Feral camels (Camelus dromedarius) eat a wide range of plants, especially shrubs and trees, including those not usually consumed by other herbivores.
Populations may increase by as much as 15% in good seasons, such as 1999-2000 in central Australia.
Source: JE Williams
About 20 species of mammals, 25 species of birds, several amphibians and 19 species of freshwater fish make up the pest vertebrate populations of Australia. TAPs have been prepared under the National Feral Animal Control Program for four of these species: the European Fox, cat, rabbit and goat. These plans focus on strategic approaches to reducing, to an acceptable level, the effects of processes that threaten the long-term survival of native species and ecological communities.
Introduced species can have a major effect on offshore islands such as Lord Howe Island and Macquarie Island. The endangered Woodhen (Tricholimnas sylvestris), one of the world's rarest bird species, is found on Lord Howe Island. During the 1900s, the population of Woodhens has declined significantly in numbers as a result of disturbance by feral animals, hunting by humans and habitat loss. Thirty-four plant and animal species have been introduced on Macquarie Island, some deliberately for human consumption. The list ranges from domestic animals (which generally did not survive the harsh conditions) to insects such as the flea, which was probably introduced with the Black Rat. The greatest environmental damage on the Island has come from introduced mammals like cats and rats that eat ground-nesting seabirds, eggs and chicks or from rabbits, which eat the vegetation and contribute to soil erosion. More remote islands such as Heard and McDonald Islands are considered free from introduced species, although introductions of microorganisms could have occurred.
Clarke et al. (2000) provided detailed descriptions of over 50 environmentally significant vertebrate and invertebrate pests in freshwater, terrestrial and marine environments (Table 39). Eight of the non-native pest animals were from freshwater habitats, over 30 from terrestrial habitats and at least 10 from marine habitats. Distribution maps have been produced for each species as well as total number of pest species per IBRA (Figure 36), drainage basin (Figure 37) and IMCRA region (Figure 38). These show that the highest numbers of pest species on both an IBRA, drainage basin and IMCRA basis occur in south-east Australia where the human population is highest.
| No. | Common name | Species name |
|---|---|---|
| Freshwater species | ||
| 1 | Brown Trout | Salmo trutta |
| 2 | Rainbow Trout | Oncorhynchus mykiss |
| 3 | English Perch | Perca fluviatilis |
| 4 | European Carp | Cyprinus carpio |
| 5 | Goldfish | Carrasius auratus |
| 6 | Guppy | Poecilia reticulata |
| 7 | Mosquitofish | Gambusia holbrooki |
| 8 | Tilapia | Oreochromis mossambicus |
| Terrestrial vertebrate species | ||
| 9 | Cat | Felis catus |
| 10 | Fox | Vulpes vulpes |
| 11 | PigA | Sus scrofa |
| 12 | RabbitA | Oryctolagus cuniculus |
| 13 | Black Rat | Rattus rattus |
| 14 | Brown Rat | Rattus norvegicus |
| 15 | House MouseA | Mus musculus |
| 16 | GoatA | Capra hircus |
| 17 | Brumby | Equus caballus |
| 18 | Deer | Axis axis Axis porcinus Cervus elaphus Cervus timoriensis Cervus unicolor Dama dama |
| 19 | Cane Toad | Bufo marinus |
| 20 | Water Buffalo | Bubalus bubalis |
| 21 | Common Starling | Sturnus vulgaris |
| 22 | Common Myna | Acridotheres tristis |
| 23 | House Sparrow | Passer domesticus |
| 24 | Eurasian Blackbird | Turdus merula |
| 25 | Mallard | Anas platyrhynchos |
| 26 | Nutmeg Mannikin | Lonchura punctulata |
| 27 | Wild Dog | Canis familiaris familiaris |
| 28 | European Honeybee | Apis mellifera |
| 29 | European Wasp | Vespula germanica |
| 30 | Black Portuguese Millipede | Ommatoiulus moreleti |
| 31 | Western Flower Thrips | Frankliniella occidentalis |
| 32 | Bumble Bee | Bombus terrestris |
| 33 | Spiralling Whitefly | Aleurodicus dispersus |
| 34 | White Snails | Theba pisana Cernuella virgata |
| 35 | Conical Snails | Cochlicella acuta Cochlicella barbara |
| 36 | Elm Bark Beetles | Scolytus multistriatus Pyrrhalta luteola |
| 37 | Crazy Ant | Anoplolepis gracilipes |
| Marine species | ||
| 38 | Mediterranean Fanworm | Sabella spallanzanii |
| 39 | Northern Pacific Seastar | Asterias amurensis |
| 40 | European Shore Crab | Carcinus maenas |
| 41 | North Pacific Oyster | Crassostrea gigas |
| 42 | New Zealand Screw Shell | Maoricolpus roseus |
| 43 | Asian Date Mussel | Musculista senhousia |
| 44 | Japanese Kelp or Wakame | Undaria pinnatifida |
| 45 | Dead Man's Fingers or Broccoli Weed | Codium fragile tomentosoides |
| 46 | Caulerpa | Caulerpa filiformis |
| 47 | Toxic Dinoflagellates | Gymnodinium catenatum Alexandrium catenella Alexandrium minutum |
| 48 | Black Striped Zebra Mussel | Mytilopsis sallei |
| Endemic pest species | ||
| 49 | Laughing Kookaburra | Dacelo novaeguineae |
| 50 | Koala | Phascolarctos cinereus |
| 51 | KangarooA- Western Grey Eastern Grey Red |
Macropus fuliginosus Macropus giganteus Macropus rufus |
| 52 | Crown-of-Thorns Starfish | Acanthaster planci |
| 53 | Harvester TermitesA | Drepanotermes perniger Drepanotermes rubriceps |
| 54 | Yabbie | Cherax destructor |
AIndicates coverage includes both managed and natural ecosystems.
Figure 36: Number of terrestrial non-indigenous vertebrate and invertebrate pest species per IBRA region based on a list of around 30 species considered to have a major impact in Australia (Table 39).
Source: Clarke et al. (2000)
Figure 37: Number of freshwater pest species per drainage basin including the endemic Yabbie (Cherax destructor).
Source: Clarke et al. (2000)
Figure 38: Number of marine pest species per IMCRA region including the endemic Crown-of-thorns Starfish (Acanthaster planci).
Source: Clarke et al. (2000)
Invertebrate species and microorganisms
About 500 introduced invertebrate species are thought to be changing the environment, including the European Honeybee (Apis mellifera) that may out-compete smaller, typically solitary Australian native bees (Paton 1996). The management of species such as the European Honeybee, which have been introduced for commercial purposes but have subsequent effects on native species, brings considerable challenges. This has also been observed with grasses introduced for pastoral purposes (see Environmental weeds). The potential for the introduction of microorganisms has not been systematically explored, but could have a significant effect on biodiversity. This could be of particular importance in remote environments such as Antarctica, where it is thought that the introduction of microorganisms is likely to have occurred.
New species continue to appear such as the recently discovered Black Striped Mussel (Congeria sallei), an invasive freshwater mussel from Central America, which was found in Darwin Harbour. Given the tolerance of this mussel to a range of temperature and salinity, it could potentially infest all Australian ports. A major program was put in place to eradicate the mussel, focusing on the application of large quantities of chlorine and copper sulfate. While the mussels are thought to be unable to survive this treatment, there is a strong chance that the species could become re-established and a national task force has been formed to combat the pest.
As so little is known about which marine species normally inhabit most ports and harbours, it is almost impossible to record the rate of introductions.
When least expected
Some introduced animals that have been around for decades can also become pests. For example, the Crazy Ant (Anoplolepis gracilipes) was introduced to Christmas Island in the 1930s, and only recently has become a major threat to biodiversity (see The threat to biodiversity on Christmas Island from the Crazy Ant). Species introduced to control pest species can also become pests themselves. The introduction of the South American Cane Toad (Bufo marinus) into Queensland in 1935 from Hawaii to control two insect pests of sugar cane was a failure. The insects were later controlled using insecticides and other management practices. Meanwhile, the Cane Toad continues to thrive relying on a range of prey including native invertebrates and small vertebrate species, and they are also thought to compete with native frogs and snakes for these foods. In addition, the toad has toxic skin secretions that are known to kill vertebrate predators such as goannas, quolls, skinks and snakes. The toads have been spreading, mainly to the north, since their introduction (Figure 39). In December 1998, they were noticed around 500 km south of Darwin. They have been found recently in as far north as the Koolatong River in east Arnhem Land to just inside the south-east corner of Kakadu National Park and throughout the Katherine River System.
The threat to biodiversity on Christmas Island from the Crazy Ant
The Crazy Ant (Anoplolepis gracilipes) has become a major threat to biodiversity on Christmas Island. It is a tropical species native to western Africa and was first found in Australia on Christmas Island in the 1930s. It has become a pest only recently there, but is already seen as a direct threat to as many as 20 animal species, including sea birds, land birds, mammals, reptiles and three species of crabs. Millions of the Red Crabs (Gecariodea natalis), for which Christmas Island is famous, have been killed by the Crazy Ant. The crab is critical to the dynamics of the unique rainforest communities on the island, so its elimination has a direct effect on forest structure and processes. The presence of Crazy Ants can also lead to canopy dieback due to the mutual relationship with scale insects that produce honeydew (scale insects cause a disease that can result in dieback; honeydew is a food source of the ant and the ants protect the scale insects from other predators). Several reasons underly the major threat imposed by these ants: their extremely broad diet, the formation of supercolonies with extraordinarily high and sustained densities, and they forage in three dimensions. Contact sprays, dusts and toxic baits have been successfully used to control the ant, and because there appears to be no native ant species on Christmas Island, biological control could be feasible long-term. Unless host specificity could be guaranteed, this method would not be suitable for mainland Australia, where the Crazy Ant has recently been recorded in the north-east of the Northern Territory.
Source: Clarke et al. (2000); Garnett and Crowley (2000).
A Crazy Ant (Anoplolepis gracilipes) feeding on the honeydew produced by scale insects.
The mutual relationship between these two species has been responsible for extensive canopy dieback on Christmas Island.
Source: Piper Films, Australia
Figure 39: Distribution and spread of Cane Toads (Bufo marinus) from 1935 to 2001.
This is an indicative map only and does not record the complexity of the invaded areas. Recent information on the southward spread of the Cane Toad was not available for this report.
Source: Burgman and Lindenmayer (1998); van Dam et al. (2000)
Environmental weeds [BD Indicator 3.2]
Environmental weeds are plants that invade natural ecosystems and can cause major modification to indigenous species and ecosystem function (as opposed to horticultural or agricultural weeds, although a species may be both). They are considered one of the greatest threats to nature conservation in Australia (Commonwealth of Australia 1999; Low 1999), having been implicated in the extinction of four plant species (Groves & Willis 1999). The most recent estimate of the number of environmental weeds in Australia is 1060 (Swarbrick & Skarrat 1994). Virtually all aquatic and terrestrial vegetation communities in Australia are affected by environmental weeds. There are, however, considerable differences in the level of invasion, both within and between vegetation types, with disturbance history and proximity to human development being key factors.
One species of great concern, the Rubber Vine (Cryptostegia grandiflora), entangles trees and other vegetation and eventually smothers them. The vine is spreading at an alarming rate through the river systems of southern Cape York, the Queensland part of the Gulf of Carpentaria and along the coast as far south as the Burnett River near Bundaberg, destroying the riverside vegetation in these regions.
For aquatic weeds, patterns of rainfall in particular have a major influence on their distribution and management. A network of people responsible for aquatic weed management is needed to gather information in order to assess the aquatic weed situation annually across Australia. Without this, it is impossible to describe the extent of effects at a national level, although several case studies for individual species are available.
Indigenous species
Not all environmental weeds are introduced from other countries. They can be indigenous species that have been deliberately planted for horticulture beyond their natural range or where altered disturbance regimes encourage their spread into areas where they did not grow previously. Despite being 'native' plants, weeds of indigenous origin can severely disrupt ecosystems. Examples are Coastal Tea-tree (Leptospermum laevigatum), Cootamundra Wattle (Acacia baileyana) and Sweet Pittosporum (Pittosporum undulatum) (Mullett 1996).
Effects of environmental weeds
Environmental weeds can have a range of effects on natural systems, although quantitative studies of these effects are uncommon (Adair & Groves 1998). Despite the paucity of studies, however, it is likely that major changes to ecosystem structure will cause consequent losses of biodiversity. This has been observed in New Zealand, where several species introduced deliberately for naturalisation in the wild have dispersed effectively from the locations in which they were planted, reducing the diversity of both plant and animal species in all cases (Williams & West 2000).
The effects of environmental weeds are not always detrimental. For example, they can provide some native animals with additional food sources and shelter. In these cases, management strategies need to reflect the supply of alternative shelter and food sources. Equally important, management options need to include consideration of the control of native dispersal agents such as birds and mammals. Weeds can be spread widely by animals, as demonstrated for species such as the Brushtail Possum.
Pasture plants
Plants legally introduced into Australia for pasture production or horticulture have the potential to become environmental weeds. Lonsdale (1994) demonstrated that greater than 99% of species introduced between 1947 and 1985 that were considered useful for pasture production caused weed problems in both cropping and conservation areas in northern Australia. Only 5% became useful for pastoral use. Mitchell and Williams (2000) described two vigorous wetland grasses introduced for ponded pastures in Queensland in the 1980s which outcompeted native plants and have drastically altered the habitat for many waterfowl. Consequently, the net benefit for Australia of introducing such species needs to be seriously considered before similar species are introduced.
An introduced pasture species that is quickly becoming a major environmental weed in central Australia is Buffel Grass (Cenchrus ciliaris). This is a perennial grass, which has been shown to reduce the diversity and abundance of both native vascular plants and invertebrates (Pitts & Albrecht 2000). Seed of this species is spread by helicopter by some pastoralists and once established it is a difficult species to control. Burning is not an effective long-term solution as the grass recovers rapidly and completely, and suppresses the germination of native plant species.
Sleeper weeds
Many of the introduced plants already in Australia may become weeds given sufficient time or a change in conditions (e.g. disturbance, introduction of a pollinator and climate change). 'Sleeper weeds' (those species that have naturalised, but not yet exponentially expanded their populations) are a major concern. Groves (1999) identified two ecological factors that were useful in predicting sleeper weeds: time from naturalisation, and relocation to a more favourable site. Some progress has been made, with recent studies identifying 'potential environmental weeds' (non-native species only) that are amenable to eradication (Csurches & Edwards 1998). There is still, however, no effective response mechanisms in place to retrospectively apply weed risk assessment to naturalised species that can still be controlled.
Nursery plants
Another source of concern is garden plants that can become potential environmental weeds. In 1999, the Nursery Industry Association identified 860 invasive plants available through nurseries. To minimise the impact of this practice, the current emphasis is on education and raising awareness, with the government, nursery industry and horticultural media working together to find solutions (Blood 1999). Currently, 50 of the plants have been voluntarily withdrawn from sale. Control of this trade is made more difficult by the complex and inconsistent approach to noxious weed legislation in Australia (Thorp & Lynch 1999).
Policies and programs for weed management [BD Indicator 19.1]
At the national level, the developing awareness during the 1990s of the threat of weed species to both production and conservation systems achieved formal recognition with the launch of the National Weeds Strategy in mid-1997.
A central component of the strategy was the identification of the most serious weed problems in Australia, which resulted in an official list of 20 Weeds of National Significance (WONS) (Table 40) (Thorp & Lynch 2000). This was developed on behalf of Agricultural and Resource Management Council of Australia and New Zealand (ARMCANZ), Australia and New Zealand Environment Conservation Council (ANZECC) and the Ministerial Council on Forestry, Fisheries and Aquaculture (MCFFA) and has been agreed with the states and territories of Australia after extensive consultation.
The final 20 species were selected from an original list of 71 species based on their invasiveness, economic, environmental and social effects, current distribution, potential for spread and effect in reducing the growth of desirable plants. Whereas all 20 species were identified as a threat to plant communities and endangered plant and animal species (Table 40), six of the weed species were classified as primarily a threat to the environment, another five as primarily a threat to primary production systems, and nine weeds have both environmental and primary production effects. Maps of the current and predicted distribution of the 20 species have been produced (e.g. Figures 40 and 41) and a major publication on the WONS has been released (Thorp & Lynch 2000). While endorsement of the list is not accompanied by any specific form of guaranteed funding, it will assist the Commonwealth, states and territories in determining funding priorities as well as providing direction to research organisations, commercial partners, industry and community groups.
| Common name Scientific name |
Origin of weed | Threats to: | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Human health & safety | Pastoral industries | Cropping industries | Forestry management | Water quality & supplies | Damage to infrastructure | Endangered species | Plant communities | Cultural values | Tourism | The community | Recreation & amenities |
||
| Alligator Weed Alternanthera philoxeroides |
North-east Argentina | x | x | x | x | x | x | x | x | x | |||
| Athel Pine Tamarix aphylla |
Northern Africa; Iran; India; Arabian Peninsula | x | x | x | x | x | x | x | x | ||||
| Bitou Bush/ Boneseed Chrysanthemoides monilifera ssp. rotundata/ molinifera | South-west South Africa | x | x | x | x | x | x | x | |||||
| Blackberry Rubus sp. | Europe | x | x | x | x | x | x | x | |||||
| Bridal Creeper Asparagus asparagoides |
South Africa | x | x | x | x | x | x | x | |||||
| Cabomba Cabomba caroliniana |
USA | x | x | x | x | x | x | x | x | x | x | x | |
| Chilean Needle Grass Nassella neesiana |
Southern America | x | x | x | x | x | |||||||
| Gorse Ulex europaeus |
Central & western Europe | x | x | x | x | x | x | x | |||||
| Hymenachne Hymenachne amplexiculis |
South & central tropical America | x | x | x | x | x | x | x | x | x | |||
| Lantana Lantana camara |
Central America | x | x | x | x | x | x | x | x | x | |||
| Mesquite Prosopis sp. | Northern South America; central America; southern USA | x | x | x | x | x | x | x | x | x | x | ||
| Mimosa Mimosa pigra |
Tropical America | x | x | x | x | x | x | x | x | x | x | x | |
| Parkinsonia Parkinsonia aculeata |
Southern USA; Caribbean, Mexico; northern South America | x | x | x | x | x | x | x | x | x | x | x | |
| Parthenium Weed Parthenium hysterophorus |
Caribbean | x | x | x | x | x | x | x | x | x | x | ||
| Pond Apple Annona glabra |
North, Central & South America; west coast of tropical Africa | x | x | x | x | x | x | x | |||||
| Prickly Acacia Acacia nilotica ssp. indica |
Africa; western Asia | x | x | x | x | x | x | x | x | x | x | x | |
| Rubber Vine Cryptostegia grandiflora |
South-west Madagascar | x | x | x | x | x | x | x | x | x | x | ||
| Salvinia Salvinia molesta |
South-east Brazil | x | x | x | x | x | x | x | x | x | x | x | |
| Serrated Tussock Nassella trichotoma |
Argentina; Peru; Chile; Uruguay | x | x | x | x | x | x | x | x | ||||
| Willows Salix spp.A | Europe; America; Asia | x | x | x | x | x | x | x | x | ||||
AExcept Weeping Willows (Salix babylonica), Pussy Willows (Salix calodendron) and Sterile Pussy Willow (Salix reichardtii).
Source: after National Weeds Strategy Executive Committee (1999) http://www.weeds.org.au/natsig.htm .
Figure 40: Current and potential distribution of Alligator Weed (Alternanthera philoxeroides), a weed of national significance.
The potential distribution used is predicted from the climate-modelling program CLIMATE, plus the remainder of the current distribution, which was not included in the prediction.
Source: Thorp and Lynch (2000)
Figure 41: Current and potential distribution of Parkinsonia (Parkinsonia aculeata), a weed of national significance.
The potential distribution used is predicted from the climate-modelling program CLIMATE, plus the remainder of the current distribution, which was not included in the prediction.
Source: Thorp and Lynch (2000)
National coordination teams are being established for each of the weed species and individual management plans prepared. The implementation of the plans has been slower than expected due to the need to engage a range of stakeholders in their development. The intention of the plans is to focus on strategic management and on species that have national priority.
Considering the number of environmental weeds in Australia, and the potential threat posed by 'sleeper weeds', there is some concern that focusing resources on a small number of nationally significant species may not be the best approach. To help complement this strategy, an 'alert list' has been developed of 28 non-native plant species that are in the early stages of establishment and have the potential to become a significant threat to biodiversity if they are not managed. Funding priority for their management or control will be given to projects that promote the long-term protection of remnant vegetation, especially ecologically threatened communities, and that target isolated populations of the weeds to prevent further establishment and expansion of the weed.
Diseases
Introduced diseases pose a major threat to biodiversity in Australia, as shown by the effect of dieback disease, caused by the fungus Phytophthora cinnamomi. This species was introduced into Australia in the 1800s, probably accompanying plant material introduced for agriculture. Dieback disease can result in great changes in a broad range of ecosystems including heathlands, shrublands, woodlands and forests. About 20% of the 9000 vascular plants of south-west Western Australia may be at risk from dieback disease, including more than 80% of all Proteaceae which are particularly susceptible. At least 10% of the remaining jarrah forest in south-west Western Australia is infected with dieback disease, although this is considered an underestimate. Changes in vegetation communities associated with Phytophthora would affect fauna, especially for species such as the Honey Possum (Tarsipes rostratus), which rely on a specialised diet of pollen and nectar mainly from highly susceptible proteaceous plants.
Phytophthora is also a problem in eastern Australia, and has been found in the highlands of Tasmania. The flora of northern Australia is also considered susceptible to Phytophthora, so several hygiene measures have been put in place to stop its introduction via potted plants brought in for horticultural purposes or use in gardens.
The extent of the threat of Phytophthora to Australia's species and ecosystems is recognised in the 1996 National Strategy for the Conservation of Australia's Biodiversity where it is the only pathogenic taxon specifically cited. The Commonwealth EPBC Act also lists the disease caused by Phytophthora as a key threatening process. A nationally coordinated threat abatement process is being developed to manage the effect of Phytophthora dieback on Australian ecosystems. A draft plan was circulated in July 1999 which estimated that over $10 million would be needed to be spent over five years to implement the plan.
Disease has also been linked to the decline of some frog populations in Australia. There is strong evidence that a chytrid fungus is associated with the death of some frogs, but it is not known if it is the direct cause of mortality or an indication of other environmental stress. Other diseases already in Australia may become a threat, in much the same manner as 'sleeper weeds' and pests.
Quarantine
Effective quarantine is a key factor in minimising the introduction of potential weeds, pests and diseases from both other countries and within Australia (see the Land Report). The recently introduced weed risk assessment was explicitly designed to detect weeds of both environmental and agricultural concern (Steinke & Walton 1999). This system has been endorsed by a wide range of client groups and is now used on all new plant imports whether they enter Australia as seeds, nursery stock or tissue culture, regardless of their use in Australia.
Managing introduced species [BD Indicator 19.1]
Integrated management
Integrated management involves coordinated use of various control techniques, and integrating control with other activities. The major aims of integrated management for environmental weeds are to (Vranjic et al. 2000):
- effectively contain the spread of existing weeds
- manage the environment to prevent the incursion of new weeds
- rehabilitate the disturbed ecosystem as far as possible.
In natural systems, this involves a range of considerations such as the use of herbicides (and their potential effects on non-target species), the appropriate situations where fire can be used and the importance of passive and active revegetation.
Biological control
Biological control is one of the tools used to manage a range of introduced organisms. The Biological Control Act 1984 is the principal enabling legislation at the Commonwealth level. Biological control is not always the 'magic bullet', particularly for terrestrial weeds with large soil seed reserves (Briese 2000). Consequently, biological control is more frequently seen as part of an overall management strategy.
One of the critical tests for new organisms being considered as biological control agents is whether they will affect other non-target organisms. Stringent tests are now enforced to help ensure that biological control agents are effective and do not become pests themselves. However, the system is not fail-safe as illustrated by the untimely escape in 1995 of rabbit calicivirus (RCD) from Wardang Island in South Australia.
Rabbit calicivirus and other management tools
Agents such as RCD, and its precursor myxomatosis, are essential management tools, given the number and extent of rabbits in Australia. RCD is highly infectious to rabbits and can cause mortalities of up to 95% among adults, although regional variation in infection rates can be significant.
While an initial reduction in rabbit populations may be brought about by an effective outbreak of viruses such as RCD or by poisoning or drought, to keep populations low, follow-up techniques such as poisoning, warren ripping and fumigation are recommended. At another level, rabbit control may need to be integrated with the control of other pest species such as foxes and feral cats. There has been some concern that the reduction in rabbit numbers may lead to predators switching their prey to native animal species.
Western Shield
The Western Shield Program, managed by CALM in Western Australia, aims to bring at least 13 fauna species back from the brink of extinction by controlling foxes and feral cats, on almost five million hectares of land.
The main weapon in the fight against the fox and feral cat is use of the naturally occurring poison 1080, found in native plants called gastrolobiums ('poison peas'). Although native animals in south-west Australia have a high tolerance to the poison, introduced animals do not. In the south-west forests, scientific research and monitoring has shown that where fox numbers have been reduced by baiting with 1080, there has been a dramatic increase in native animal numbers.
Endangered native animals such as the Numbat (Myrmecobius fasciatus), Noisy Scrub-bird (Atrichornis clamosus) and Ring-Tailed Possum (Petropseudes dahli) are increasing in numbers after being reintroduced into forest inside and outside reserves. Already, three forest-dwelling mammals, the Woylie (Bettongia pencillata), Quenda or Southern Brown Bandicoot (Isoodon obesulus) and Tammar Wallaby (Macropus eugenii) have been removed from the State's Threatened Fauna List and the status of other species has been improved as a result of successful conservation management under the Western Shield Program.
Community involvement
The successful management of pests and weeds requires the informed and motivated participation of people throughout Australia. An important element of the success of the Western Shield Program described above is the cooperation and support of local communities. Many private landowners and Land Conservation District Committees have helped with fox baiting by laying baits on their own land where it is next to conservation reserves and state forests. As well as government funding, the baiting program is sponsored by Alcoa Australia, Cable Sands and Westralian Sands.
The Ballarat Region Gorse Task Force in Victoria is another example that involves a range of groups in the management of an environmental weed (see Ballarat Region gorse (Ulex europaeus) Task Force).
Gorse (Ulex europaeus) is a serious environmental and agricultural weed in south-east Australia because of its invasiveness and the difficulty and expense involved in conventional control. It invades bushland, reducing access and conservation values and threatening the survival of rare and endangered plants. On pastoral land, gorse significantly reduces pasture and animal productivity. Gorse also provides habitat and shelter for vertebrate pests such as rabbits and foxes, and increases fire hazards. In Victoria, gorse is common in the central highlands, the south-west and parts of Gippsland.
The Gorse Task Force Area is centred on Ballarat and covers some 800 000 ha of urban, farming and forested land in the central highlands of Victoria.
The Ballarat Region Gorse Task Force represents 43 Landcare groups across the central highlands of Victoria. The Task Force has prepared a Gorse Control Strategy which targets infestations along roadsides and waterways where the greatest potential for spread exists, and where there is a demonstrated public benefit associated with control.
The Task Force approach is based on a model with strong partnerships between landholders and Landcare groups, local government, catchment management authorities and the Department of Natural Resources and Environment (DNRE). The model empowers community groups to lead and coordinate the implementation of agreed community-based weed control strategies. The role of DNRE is to support these strategies through providing community education, extension and enforcement programs to ensure that a lack of action by a minority does not jeopardise the good work of most of the community.
The Gorse Task Force has secured funding for implementation of the Gorse Control Strategy, including the employment of facilitators and provision of incentives for onground control where there is a demonstrated public benefit. DNRE have provided compliance officers, funded through their 'Enhanced Enforcement' program. The Strategy identifies facilitation as the key to raising community awareness of the problems caused by gorse, for coordinating strategic programs for long-term management, and most importantly, for creating community acceptance of responsibility for gorse control.
Source: DNRE, Victoria.
Funding and research into exotic organisms [BD Indicator 19.2 and 19.3]
Environmental weeds
An indication of the nature of the research on environmental weeds can be gained through the annotated bibliography developed by Swarbrick and Timmins (1997). At the national level, the main focus of research has been through two CRCs: Tropical Pest Management in northern Australia and Weed Management Systems in southern Australia, established in 1995. The former CRC ceased operation in 1998, but individual organisations are still working on the ecology of environmental weeds in the north.
The Weed Management Systems CRC has worked on seven 'key' environmental weeds: Bitou Bush (Chrysanthemoides monilifera ssp. rotundata), Boneseed (Chrysanthemoides monilifera ssp. monilifera), Bridal Creeper (Asparagus asparagoides), Broom (Cytisus scoparius), Blackberry (Rubus fruticosus), Horehound (Marrubium vulgare) and St John's Wort (Hypericum perforatum).
In 2001, the CRC for Weed Management Systems was granted a further seven years of funding. This new CRC for Australian Weed Management has two programs of relevance to environmental weeds. The 'Landscape Management' Program will focus on the management of key habitats to control weeds, the management of model weed types and enhanced biocontrol strategies. A 'Weed Incursion and Risk Management' Program is also being developed that will examine risk assessment (see Risk assessment and management approaches to biodiversity) and management of sleeper weeds.
At the national level, the main source of funding for environmental weeds is through the National Weeds Program. From 1996 to 2002, a sum of $28.5 million has been allocated to this Program (see Natural Heritage Trust expenditure). In May 2001, the Commonwealth government announced funding through this Program for onground projects related to the management of established weeds that could pose a significant threat to biodiversity (as identified in the 'Alert list' of 28 species).
Pest Animals
The CRC for Biological Control of Pest Animals started in 1999 and builds on the work of the CRC for Vertebrate Biocontrol. The research focus of the CRC is to develop ways to control populations of the rabbit, fox and introduced house mouse through using vaccines that cause sterility. Before sterilisation for these animals becomes a reality, many ecological hurdles will need to be identified and overcome.
The total resources involved in the CRC for biological control is estimated to be around $57 million over seven years. The Centre has 20 postgraduate students and the equivalent of 51 full-time research staff. At the national level, $18.9 million was allocated to the National Feral Animals Control Program between 1996 and 2002 (see Natural Heritage Trust expenditure).