Impact Assessment - African daisy (Senecio pterophorus) 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?	Woody, bushy shrub. Invades dry sclerophyll forest and woodland. Generally 1 to 1.5 m in height. “In rainfall areas >500 mm pa can reach 3 m height and 2 – 2.5 m in diameter.” Potential to limit the activities of bushwalkers.	P & C (2001) Carr et al (1992)	ML
2. Reduce tourism?	Weeds presence is obvious, particularly during flowering, November to autumn. Major negative affect on aesthetics.	P & C (2001)	MH
3. Injurious to people?	Not known to affect humans.		L
4. Damage to cultural sites?	Existence of plant is quite noticeable, but is not likely to cause any structural changes.	P & C (2001)	ML
Abiotic
5. Impact flow?	Terrestrial sp.	P & C (2001)	L
6. Impact water quality?	Terrestrial sp.	P & C (2001)	L
7. Increase soil erosion?	Perennial. Fibrous, densely branching roots to 20 cm depth and up to 6 m in diameter.	P & C (2001)	L
8. Reduce biomass?	“It competes aggressively with developing pastures and crops, and becomes dominant in the early years of infestation.” Bushy property of plant suggests biomass not negatively affected. However, in woodland areas it is likely to reduce biomass.	P & C (2001) Carr et al (1992)	ML
9. Change fire regime?	While predominantly a weed of open areas (e.g. pastures, wasteland), as a woody, bushy shrub, it may have a minor impact on frequency of fire in native ecosystems.	Carr et al (1992)	ML
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Plains grassy woodland (E); CMA=Glenelg Hopkins; Bioreg=Goldfields; VH CLIMATE potential In the Mt Napier State park, it occurs in, “large patches significantly altering native vegetation.” Invades lowland grassland & grassy woodlands, dry sclerophyll forest and woodlands. Major displacement of species within different strata.	DNRE (1996)1 Carr et al (1992)	MH
(b) medium value EVC	EVC=Box-Ironbark forest (D); CMA=Glenelg Hopkins; Bioreg=Goldfields; VH CLIMATE potential Can occur on forest margins. Minor impact on grasses/forbs.	P & C (2001)	ML
(c) low value EVC	EVC=Montane dry woodland (LC); CMA=West Gippsland; Bioreg=Highland Southern Falls; VH CLIMATE potential. Can occur on forest margins. Minor impact on grasses/forbs.	P & C (2001)	ML
11. Impact on structure?	In the Mt Napier State park, it occurs in, “large patches significantly altering native vegetation.” Invades lowland grassland & grassy woodlands, dry sclerophyll forest and woodlands. Likely to have a minor impact on lower strata.	DNRE (1996) Carr et al (1992)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	“In natural areas the plant is a strong competitor, forming dense thickets that exclude native species.” Reduction in habitat for non-threatened fauna.	LC0196 (2000)2	ML
15. Benefits fauna?	None recorded.		H
16. Injurious to fauna?	Plant contains alkaloids. May be hazardous.	P & C (2001)	H
Pest Animal
17. Food source to pests?	See comment at Q16.	P & C (2001)	L
18. Provides harbor?	“In natural areas the plant is a strong competitor, forming dense thickets.” This growth habit may provide harbor for birds.	LC0196 (2000)	ML
Agriculture
19. Impact yield?	“Competes aggressively with developing pastures and crops…and often becomes dominant in early years of infestation rendering infested lands unproductive.”	P & C (2001)	H
20. Impact quality?	No recorded impact on agricultural quality.		L
21. Affect land value?	“…heavily infested lands (become) unproductive.”	P & C (2001)	M
22. Change land use?	See question 23 above. “Left undisturbed, however, it gradually thins out and is rarely a problem in well managed pastures and cereal crops.”	P & C (2001)	L
23. Increase harvest costs?	No evidence of increased harvest costs. “…it is rarely a problem in well managed cereal crops.”	P & C (2001)	L
24. Disease host/vector?	Not evident.		L