Impact Assessment - Holly leaved senecio (Senecio glastifolius) 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 Holly leaved senecio

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: Holly leaved senecio
Scientific name: Senecio glastifolius

Question	Comments	Rating	Confidence
Recreation
1. Restrict human access?	As a short-lived herbaceous perennial (Williams et al, 1999) it is not likely to prevent human access to any destination.	L	H
2. Reduce tourism?	1 - 1.5 m tall, occasionally up to 2 m, to 0.5 m wide, pink to mauve to nearly white daisy flowers. “Most conspicuous to the casual observer where it grows on road cuttings and banks…The most obvious impact …is aesthetic-it is a spectacular plant” (Williams et al, 1999). Although it is not “native-looking,” the plant is cultivated in gardens for its “cheerful flowers” (van der Walt, 2002) which wouldn’t bother most people.	ML	H
3. Injurious to people?	“Hand pulling…required thick gloves and trousers” (Brown & Brooks, 2002). “The edges of the…leaves are coarsely toothed and can be quite prickly” (van der Walt, 2002). The toothed edges of the leaves may cause some discomfort if grasped, but unlikely to cause injury to most people.	ML	MH
4. Damage to cultural sites?	At 1 - 2 m tall and with pink to mauve to nearly white daisy flowers (Williams et al, 1999) this plant may have a moderate visual effect on the aesthetics of cultural sites.	ML	H
Abiotic
5. Impact flow?	As it is “unlikely to tolerate permanently saturated soils” (Williams et al, 1999), it is unlikely to grow near enough to waterways to impact on them.	L	H
6. Impact water quality?	As it is “unlikely to tolerate permanently saturated soils” (Williams et al, 1999), it is unlikely to grow near enough to waterways to impact on them.	L	H
7. Increase soil erosion?	Displacing low-growing herbs and ferns and preventing establishment of native seedlings (Dept. cons., 2002). Ability to dominate understorey vegetation in open damp areas (CRC Weed Management, 2003). Given its ability to replace native vegetation and that “in drought conditions it may not grow at all over summer” (Williams et al., 1999), S. glastifolius may leave patches of soil that could be prone to soil erosion until there is enough soil moisture for the Senecio to germinate and establish. Without evidence of this having happened and no record of it forming monocultures, the likelihood of this occurring is presumed moderate, given the chain of events that would have to occur.	ML	MH
8. Reduce biomass?	“Seems to have a particular affinity for the open areas of scree and bare ground between the shrubs…[some species] vulnerable to shading by the invasion” (Williams et al,1999). When colonising bare ground this plant would increase biomass. Where it prevents the establishment of native vegetation it may replace or slightly increase or decrease biomass depending on the type of vegetation that it suppresses. Given the sparse nature of the sites that it tends to invade and its “strong association with sparsely vegetated sites,” (Williams et al, 1999) on balance it is likely to slightly increase biomass, but as a shortlived perennial will not act as a carbon sink.	ML	H
9. Change fire regime?	Whilst fire seems to stimulate germination (see Brown & Brooks, 2002), there is no evidence of mature plants surviving fire. As an herbaceous perennial (i.e. not woody) that tends to fall over as it grows older (Williams, 1999) there is no evidence that it provides fuel for fire. As it can replace native vegetation, it has the potential to reduce the incidence and perhaps the intensity of fires in some vegetation types e.g. Grasslands and possible heaths, but the effect would probably be minor.	ML	H
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Coast Banksia Woodland (V), CMA=West Gippsland, Bioreg.=Gippsland Plain, CLIMATE=VH. Ability to dominate understorey vegetation in open damp areas (CRC Weed Management). There is the potential for this plant to cause major displacement of some dominant species in the grass and herb layers.	MH	MH
(b) medium value EVC	EVC=Coastal Alkaline Scrub (D), CMA=West Gippsland, Bioreg.=Gippsland Plain, CLIMATE=VH. Ability to dominate understorey vegetation in open damp areas (CRC Weed Management). There is the potential for this plant to cause major displacement of some dominant species in the grass and herb layers.	MH	MH
(c) low value EVC	EVC=Heathy Woodland (LC), CMA=West Gippsland, Bioreg.=Gippsland Plain, CLIMATE=VH. Ability to dominate understorey vegetation in open damp areas (CRC Weed Management). There is the potential for this plant to cause major displacement of some dominant species in the grass and herb layers	MH	MH
11. Impact on structure?	Ability to dominate understorey vegetation in open damp areas (CRC Weed Management). There is the potential for this plant to have a major effect on the grass and herb layers and a minor effect on the low shrub layer of some communities.	MH	MH
12. Effect on threatened flora?	No information found.	MH	L
Fauna
13. Effect on threatened fauna?	No information found.	MH	L
14. Effect on non-threatened fauna?	Displacing low-growing herbs and ferns and preventing establishment of native seedlings (Dept. cons., 2002). Ability to dominate understorey vegetation in open damp areas (CRC Weed Management, 2003). There is the potential for a minor effect on food sources and/or shelter for some fauna.	ML	MH
15. Benefits fauna?	As it is eaten by the larvae of the native magpie moth and diurnal moth in NZ and seems to be palatable to sheep (Williams et al, 1999), it may provide an alternative food source for some animals.	L	H
16. Injurious to fauna?	Although it is somewhat prickly (Williams, 1999), S. glastifolius is unlikely to cause fauna to lose condition.	L	H
Pest Animal
17. Food source to pests?	Although recorded as palatable it is not noted as a food source for pests in Williams et al (1999).	L	H
18. Provides harbor?	As an herbaceous perennial with widely spaced branches (CRC Weed Management, 2003), this plant is unlikely to provide habitat or harbor for pest species.	L	MH
Agriculture
19. Impact yield?	Occurs naturally in pastoral areas. A general agricultural weed (Williams et al, 1999). However it is palatable to sheep (Williams et al, 1999), so it may simply provide an alternative fodder source and its ability to out compete pasture would probably be controlled by grazing.	L	H
20. Impact quality?	See q. 19, the plant is unlikely to reduce form in stock and does not have spines or burrs that might affect meat or wool quality.	L	H
21. Affect land value?	See q. 19, without significantly reducing yield or quality, land value is unlikely to be affected.	L	H
22. Change land use?	Would not require a change in land use.	L	H
23. Increase harvest costs?	“A troublesome weed in newly planted plantations” (Williams et al, 1999). Possibly increases harvest costs in weed control costs.	M	L
24. Disease host/vector?	None recorded	L	L

This table can also be viewed as a PDF document (printer friendly).

Impact Assessment Record - Holly leaved senecio (PDF - 24KB)
Impact Assessment Record - Holly leaved senecio (DOC - 69KB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

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