Impact Assessment - Sallow wattle (Acacia longifolia) in Victoria

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Assessment of plant invasiveness is done by evaluating biological and ecological characteristics such as germination requirements, growth rate, competitive ability, reproduction methods and dispersal mechanisms. Assessment of plant impacts, however, is determined by the extent to which a plant affects a land manager’s environmental, economic and social resources.

The relative importance of these resources varies depending upon the value people place on them and, as such, the assessment process is subjective. For example, a farmer is likely to place a higher emphasis on the impact of a plant on production (economic resource) than its impact on areas of natural vegetation occurring on the farm. Conversely, a Landcare or Friends group would value environmental or social resources more than economic resources.

Recognising that the value of resources vary between different land tenures, plant impact assessments allow a prioritisation of resources by land managers. Assessments can apply at a local, regional or state level, and the relative values of each resource identified may differ at each level.

The impact assessment method used in the Victorian Pest Plant Prioritisation Process uses three broad resource categories: social, environmental and agricultural, each with a number of related attributes. For example, social resources include such attributes as how the plant affects human access for recreation, or if it creates a health risk due to toxicity or by producing allergens.

Each resource attribute, or criterion, is assessed relative to a list of intensity ratings. Depending upon information found in relation to each criterion, a rating of Low, Medium Low, Medium High or High is assigned. Descriptions of the impact criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the impact of Sallow wattle.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

Common Name: Sallow wattle
Scientific name: Acacia longifolia (Andr.) Willd.

Question	Comments	Rating	Confidence
Recreation
1. Restrict human access?	A. longifolia produces dense thickets to 8 m (Weber 2003) which may impede individual access and cause difficulty for vehicle access.	MH	MH
2. Reduce tourism?	A. longifolia is an upright spreading bushy shrubs to small trees; 1 - 8 m, which may produce dense thickets. Also produces bright yellow flowers to 5 cm in length (Weber 2003). May cause minor effect to aesthetics.	ML	MH
3. Injurious to people?	Reported by PIER (2007), as not being toxic to humans and not to cause allergies. No other reviewed documentation suggests the plant is injurious to people.	L	M
4. Damage to cultural sites?	No reviewed documentation suggests the plant causes damage to indigenous, european heritage sites or infrastructure. Little or negligible effect on aesthetics or structure of site.	L	M
Abiotic
5. Impact flow?	Unknown: No reviewed documentation suggests that A. longifolia impacts upon water flows within watercourses or waterbodies.	M	L
6. Impact water quality?	Unknown: No reviewed documentation suggests that A. longifolia impacts on water quality.	M	L
7. Increase soil erosion?	A. longifolia was introduced into South Africa as a dune binder and stabiliser to reduce erosion (Hagemann and Rose 1988: Pieterse and Cairns 1988). May decrease the probability of soil erosion.	L	H
8. Reduce biomass?	Dense stands will shade out many ground-flora species, crowd out shrubs and severely impede overstorey regeneration (Muyt 2001). The plant produces large amounts of litter increasing nitrogen and phosphorus content in the soil (Weber 2003). This may mean A. longifolia directly replaces biomass.	ML	MH
9. Change fire regime?	Dense stands of A. longifolia can burn at high intensities (Pieterse and Cairns 1988). Mass germination of seeds occurs when stimulated by fire, so fire increased frequency would benefit the species (Pieterse and Cairns 1986). A. longifolia may cause moderate change to the intensity of fire risk.	MH	MH
Community Habitat
10. Impact on composition (a) high value EVC	EVC= Coastal Headland Scrub (V); CMA= Corangamite; Bioreg= Otway Plain; CLIMATE potential=VH. Where invasive, dense thickets may reduce native plant species richness (Weber 2003). A. longifolia encroaches into coastal interiors replacing indigenous flora and valuable natural grassland (Hagemann and Rose 1988). Dense stands will shade out many ground-flora species, crowd out shrubs and severely impede overstorey regeneration (Muyt 2001). A. longifolia is described as forming dense monocultures (Pieterse and Cairns 1988).	H	H
(b) medium value EVC	EVC= Coastal Dune Scrub/Coastal Dune Grassland Mosaic (D); CMA= Corangamite; Bioreg= Otway Plain; CLIMATE potential=VH. Where invasive, dense thickets may reduce native plant species richness (Weber 2003). A. longifolia encroaches into coastal interiors replacing indigenous flora and valuable natural grassland (Hagemann and Rose 1988). Dense stands will shade out many ground-flora species, crowd out shrubs and severely impede overstorey regeneration (Muyt 2001). A. longifolia is described as forming dense monocultures (Pieterse and Cairns 1988).	H	H
(c) low value EVC	EVC= Dunefield Heathland (LC); CMA= Mallee; Bioreg= Lowan Mallee; CLIMATE potential=VH. Where invasive, dense thickets may reduce native plant species richness (Weber 2003). A. longifolia encroaches into coastal interiors replacing indigenous flora and valuable natural grassland (Hagemann and Rose 1988). Dense stands will shade out many ground-flora species, crowd out shrubs and severely impede overstorey regeneration (Muyt 2001). A. longifolia is described as forming dense monocultures (Pieterse and Cairns 1988).	H	H
11. Impact on structure?	Dense stands will shade out many ground-flora species, crowd out shrubs and severely impede overstorey regeneration (Muyt 2001). A. longifolia has encroached into the coastal interior replacing indigenous flora and valuable natural grassland (Hagemann and Rose 1988). Plant communities in dunes, naturally characterised by open structure and low cover can be transformed into Acacia woodlands, with arboreal structure, higher cover and low species number, decreasing species richness (Marchante et al. 2003). Pieterse and Cairns (1988) describe A. longifolia forming dense monocultures.	H	H
12. Effect on threatened flora?	Dense thickets may reduce native plant species richness (Weber 2003). A. longifolia may replace indigenous flora and valuable natural grassland (Hagemann and Rose 1988). A Portuguese study found A. longifolia prevents the germination of therophytes and hemicryptophytes (Marchante et al. 2003). Although no specific information is documented on the effect of A. longifolia on VROT species.	MH	L
Fauna
13. Effect on threatened fauna?	No specific information was found to document the effect of A. longifolia on threatened fauna species.	MH	L
14. Effect on non-threatened fauna?	Where A. longifolia is invasive, dense thickets may reduce native invertebrate species richness (Weber 2003), reducing habitat and displacing individuals but not causing local extinction.	MH	M
15. Benefits fauna?	May provide as a food source for native invertebrates (Muyt 2001). Although no other specific information is documented on the benefits of A. longifolia for indigenous fauna.	MH	MH
16. Injurious to fauna?	Everist (1981) recorded stock poisoning by A. longifolia believing the toxic substance to be cyanides in the leaves. Although, no specific information was found to document that A. longifolia is injurious to indigenous fauna species.	ML	M
Pest Animal
17. Food source to pests?	No specific information was found to document that A. longifolia provides a food source to assist in success of pest animals.	M	L
18. Provides harbour?	No specific information was found to document that A. longifolia provides as important habitat or harbour for serious pests. Although A. longifolia produces dense thickets to 8 m (Weber 2003) which may provide harbour for serious pest species.	M	M
Agriculture
19. Impact yield?	Everist (1981) recorded stock poisoning by A. longifolia believing the toxic substance to be cyanides in the leaves.	ML	MH
20. Impact quality?	Not described as a weed of agriculture. No literature suggests that A. longifolia impacts on the quality of agriculture.	L	M
21. Affect land value?	Not described as a weed of agriculture. No literature suggests that A. longifolia affects land value.	L	M
22. Change land use?	Not described as a weed of agriculture. No literature suggests that A. longifolia causes a change in priority of land use.	L	M
23. Increase harvest costs?	Not described as a weed of agriculture. No literature suggests that the presence A. longifolia increases the cost of production.	L	M
24. Disease host/vector?	A fungal disease of A. longifolia has been documented in South Africa. The disease starts as a leaf spot on small seedlings and proceeds to a lethal infection. The cause of the disease of A. longifolia was noted as Clindrocladium scoparium which is known as a widespread pathogen (Hagemann and Rose 1988) in agricultural systems including conifer and hardwood seedling (Forest Pests 2006). A. longifolia may provide host to a minor disease of agriculture.	M	MH

Impact Assessment Record - Sallow wattle (PDF - 163KB)
Impact Assessment Record - Sallow wattle (DOC - 62KB)

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