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Impact Assessment - Red cestrum (Cestrum elegans) 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 Red cestrum.

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: Red cestrum
Scientific name: Cestrum elegans

Question
Comments
Rating
Confidence
Recreation
1. Restrict human access?Little, or no, effects expected in literature reviewed. However, as it forms dense thickets (Muyt, 2001), and shrub grows to over 2 m, it may be extrapolated that it may cause restrictions.
ML
M
2. Reduce tourism?Little, or no, effects expected in literature reviewed. However, as it forms dense thickets that exclude all other vegetation (Muyt, 2001) it may be extrapolated that it may reduce tourism through reduced access to preferable sites/regions/flora.
ML
M
3. Injurious to people?All parts of this plant are highly toxic (O’Hara, undated) if ingested (Dave’s garden website) Some people develop skin rashes from handling plant parts (Muyt, 2001)
H
MH
4. Damage to cultural sites?Little, or no, effects expected in literature reviewed. However, as it forms dense thickets that exclude all other vegetation (Muyt, 2001) and shrub grows to over 2 m, it may be extrapolated that it may cause adverse effects to cultural sites.
ML
M
Abiotic
5. Impact flow?Terrestrial species; therefore little or no effects expected.
L
L
6. Impact water quality?Terrestrial species; therefore little or no effects expected.
L
L
7. Increase soil erosion?Terrestrial species; therefore little or no effects expected.
L
L
8. Reduce biomass?Little, or no, effects discussed in literature reviewed. However, as it forms dense thickets (Muyt, 2001) it may be extrapolated that it may cause effects.
L
M
9. Change fire regime?Fire combustibility was unmentioned in literature reviewed. Little, or no, effects discussed in literature reviewed. However, as it forms dense thickets (Muyt, 2001) it may be extrapolated that it may cause adverse effects by a build up of fuel load.
ML
M
Community Habitat
10. Impact on composition
(a) high value EVC
EVC = Sedgy Riparian Woodland (V); CMA = Corangamite; Bioreg = Otway Ranges; VH CLIMATE potential.
It grows best in riparian forests (Muyt, ’01). Fast growth that forms dense thickets that exclude all other vegetation (Ibid.). May form monoculture within a specific layer; displace all spp. within a strata/layer.
H
MH
(b) medium value EVCEVC = Lowland Forest (D); CMA = Corangamite; Bioreg = Otway Ranges; VH CLIMATE potential.
It grows best in riparian forests (Muyt, ’01). Fairly drought tolerant (Dave’s Garden website). Fast growth that forms dense thickets that exclude all other vegetation (Ibid.). May form monoculture within a specific layer; displace all spp. within a strata/layer.
H
MH
(c) low value EVCEVC = Riparian Forest (LC); CMA = Corangamite; Bioreg = Otway Ranges; VH CLIMATE potential.
It grows best in riparian forests (Muyt, ’01). Fairly drought tolerant (Dave’s Garden website). Fast growth that forms dense thickets that exclude all other vegetation (Ibid.). May form monoculture within a specific layer; displace all spp. within a strata/layer.
H
MH
11. Impact on structure?May form monoculture/dense thickets that exclude all other vegetation (Muyt, 2001).
H
MH
12. Effect on threatened flora?Given suitable conditions, it may form dense thickets that exclude all other vegetation (Muyt, 2001).
ML
MH
Fauna
13. Effect on threatened fauna?All parts of this plant are highly toxic (Muyt, 2001, O’Hara, undated) if ingested (Dave’s garden website).
ML
MH
14. Effect on non-threatened fauna?All parts of this plant are highly toxic (Muyt, 2001, O’Hara, undated) if ingested (Dave’s garden website).
Attracts butterflies (Top Tropicals website).
ML
MH
15. Benefits fauna?Little or no effects discussed in literature reviewed.
M
L
16. Injurious to fauna?All parts of this plant are highly toxic (Muyt, 2001, O’Hara, undated) if ingested (Dave’s garden website).
H
MH
Pest Animal
17. Food source to pests?All parts of this plant are highly toxic (O’Hara, undated) if ingested (Dave’s garden website); but berries produced to attract mobile eaters.
ML
L
18. Provides harbour?May form dense thickets (Muyt, 2001) of shrubs to over 2 m., although no animals were specifically mentioned as harbouring in these thickets, this doesn’t mean they don’t.
ML
L
Agriculture
19. Impact yield?Not a known weed of agriculture, therefore little or no effects expected in literature reviewed.
L
L
20. Impact quality?Not a known weed of agriculture, therefore little or no effects expected in literature reviewed.
L
L
21. Affect land value?Not a known weed of agriculture, therefore little or no effects expected in literature reviewed.
L
L
22. Change land use?Not a known weed of agriculture, therefore little or no effects expected in literature reviewed.
L
L
23. Increase harvest costs?Not a known weed of agriculture, therefore little or no effects expected in literature reviewed.
L
L
24. Disease host/vector?Not a known host/vector, therefore little or no effects expected in literature reviewed.
L
L

Impact Assessment Record - Red cestrum (PDF - 96KB)
Impact Assessment Record - Red cestrum (DOC - 55KB)
This table can also be viewed as a PDF document (printer friendly). 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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