Impact Assessment - Saffron thistle (Carthamus lanatus) in Victoria (Nox)

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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.

Question	Comments	Reference	Rating
Recreation
1. Restrict human access?	An erect annual herb commonly 40 to 90 cm high. Saffron thistle grows on disturbed sites of low fertility and, “often grows in dense patches which restrict stock movement.” Patches may inhibit direct access.	P & C (2001)	ML
2. Reduce tourism?	The flower stems are rigid and the leaves are reflexed and rigid, and armed with stout spines. Dense patches may restrict some recreational activities.	P & C (2001)	MH
3. Injurious to people?	The flower stems are rigid and the leaves are reflexed and rigid, and armed with stout spines. Spines are present for most of the year.	P & C (2001)	MH
4. Damage to cultural sites?	Dense patches would create a negative visual impact the spiny nature of the plant would seriously affect the aesthetics of a cultural site. An annual herb, the root system would not cause structural damage.		ML
Abiotic
5. Impact flow?	Terrestrial species.	P & C (2001)	L
6. Impact water quality?	Terrestrial species.	P & C (2001)	L
7. Increase soil erosion?	“In the Western Plains of New South Wales, C. lanatus helped to provide ground cover and prevent erosion.”	Groves et al (1995)	L
8. Reduce biomass?	Direct replacement of biomass by invader.		ML
9. Change fire regime?	When the plant dies it leaves very little fuel to establish or support fire.		L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Plains grassy woodland (E); CMA=Glenelg Hopkins; Bioreg=Victorian Volcanic Plain; VH CLIMATE potential. “Saffron thistle often occurs in dense patches. [However, it] does not invade perennial pastures.” In Victoria, it occurs in small populations. Minor impact on grasses/forbs.	P & C (2001) Carr et al (1992)	ML
(b) medium value EVC	EVC=Plains sedgy woodland (E); CMA=Glenelg Hopkins; Bioreg=Dundas Tablelands; VH CLIMATE potential. Impact as in 10(a) above.	P & C (2001) Carr et al (1992)	ML
(c) low value EVC	Does not appear likely to occur in low value EVCs in Victoria.		L
11. Impact on structure?	C. lanatus is widespread across Victoria in small populations. It is found in lowland grassland and grassy woodland. It establishes on disturbed sites competing for moisture, light and soil nutrients. Minor effect <60% of the floral strata.	Carr et al (1992) Groves et al (1995)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	Competes with perennial grasses and, as the stout spines discourage grazing, it would reduce the food source for native species.	Groves et al (1995)	ML
15. Benefits fauna?	“Several reports from New South Wales and South Australia have indicated that C. lanatus have some feed value.”	Groves et al (1995)	MH
16. Injurious to fauna?	“Causes or predisposes the livestock to eye and mouth injury.” Potential to injure fauna.	Groves et al (1995)	H
Pest Animal
17. Food source to pests?	Not known as a food source to pests.		L
18. Provides harbour?	Not known to provide harbour.		L
Agriculture
19. Impact yield?	“Restricts or eliminates pasture growth in low fertility soils, thereby reducing carrying capacity and preventing livestock grazing. Reduces grain yield by 50–70%.” Serious impact on agricultural yield.	Groves et al (1995)	H
20. Impact quality?	“Seeds and broken plant parts contaminate wheat, leading to dockage by the Australian Wheat Board. It also causes vegetable fault in wool.” “Produce such as hay or seed which contains seeds of any noxious weed is usually prohibited from sale.”	P & C (2001) Groves et al (1995)	H
21. Affect land value?	“Decreases property values and potential income.”	Groves et al (1995)	H
22. Change land use?	“A persistent approach [to control] is necessary. One effective program combines cropping and pasture establishment.” Change to land use in grazing situations. Alternatively, goats can be used to control infestations.	P & C (2001)	M
23. Increase harvest costs?	“…the hard stems increase wear and tear on harvesting machinery.”	P & C (2001)	M
24. Disease host/vector?	“There is veterinary evidence that the spiny leaves and bracts are involved in transmitting virus diseases in grazing animals.”	P & C (2001)	M

Impact Assessment Record - Saffron thistle (PDF - 32KB)
Impact Assessment Record - Saffron thistle (DOC - 60KB)
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