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Impact Assessment - Cape ivy (Delairea odorata) 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 Cape ivy.

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: Cape ivy
Scientific name: Delairea odorata

Question
Comments
Rating
Confidence
Recreation
1. Restrict human access?Can from dense tangled curtains of vegetation, including in riparian areas (Muyt 2001). Access would be difficult and would require significant works to control the species to maintain access due to the species rapid growth.
MH
MH
2. Reduce tourism?Fragrant ornamental species can alter aesthetics (Blood 2001).
ML
MH
3. Injurious to people?Toxic to people (Richardson, Richardson & Shepherd 2006). Toxins include pyrrolizidine alkaloids and xanthones, which are contained in the leaves and present all year (Bossard, Randell & Hoshovsky 2000). No reported fatalities.
MH
MH
4. Damage to cultural sites?Fragrant ornamental species could alter aesthetics (Blood 2001).
ML
L
Abiotic
5. Impact flow?Flood mitigation strategies can be impacted upon by this species invading riparian areas (Bossard, Randell & Hoshovsky 2000).
ML
MH
6. Impact water quality?No reported evidence that this species impacts on water quality factors such as dissolved oxygen or temperature.
However the plant is said to contain compounds that are toxic to fish and may be released into the water (Bossard, Randell & Hoshovsky 2000).
L
M
7. Increase soil erosion?Can contribute to soil erosion on hillsides (Bossard, Randell & Hoshovsky 2000).
MH
MH
8. Reduce biomass?The weight of the ivy can cause trees to fall, and dense canopy of the vine can smother species of the lower strata and reduce growth (Bossard, Randell & Hoshovsky 2000).
MH
MH
9. Change fire regime?Foliage has high moisture content (Bossard, Randell & Hoshovsky 2000).
This would constitute a change in fuel properties and have some impact on fire intensity (Brooks et al 2004).
ML
H
Community Habitat
10. Impact on composition
(a) high value EVC
EVC= Riparian Forest (V); CMA= Corangamite; Bioreg= Otway Plain; VH CLIMATE potential.
The weight of the ivy can cause trees to fall, the dense canopy of the vine can smother species of the lower strata and reduce growth and regeneration of species and can form monocultures (Bossard, Randell & Hoshovsky 2000).
H
MH
(b) medium value EVCEVC= Lowland Forest (D); CMA= Corangamite; Bioreg= Otway Plain; VH CLIMATE potential.
The weight of the ivy can cause trees to fall, the dense canopy of the vine can smother species of the lower strata and reduce growth and regeneration of species and can form monocultures (Bossard, Randell & Hoshovsky 2000).
H
MH
(c) low value EVCEVC= Wet Forest (LC); CMA= Corangamite; Bioreg= Otway Plain; VH CLIMATE potential.
The weight of the ivy can cause trees to fall, the dense canopy of the vine can smother species of the lower strata and reduce growth and regeneration of species and can form monocultures (Bossard, Randell & Hoshovsky 2000).
H
MH
11. Impact on structure?The weight of the ivy can cause trees to fall, and the dense canopy of the vine can smother species of the lower strata and reduce growth and regeneration of species (Bossard, Randell & Hoshovsky 2000).
MH
MH
12. Effect on threatened flora?Can significantly reduce the species richness and diversity of an area, and render habitat in protected reserves for plant species worthless (Bossard, Randell & Hoshovsky 2000).
MH
M
Fauna
13. Effect on threatened fauna?Can render habitat in protected reserves for animal species worthless (Bossard, Randell & Hoshovsky 2000).
MH
M
14. Effect on non-threatened fauna?Significant alteration of habitat; reducing plant species richness and diversity and therefore diversity of food and shelter available. Invasion by cape ivy can render habitat in protected reserves for animal species worthless (Bossard, Randell & Hoshovsky 2000).
MH
MH
15. Benefits fauna?Nothing reported. Insects may visit flowers, dense foliage may provide some shelter.
H
M
16. Injurious to fauna?Foliage contains compounds toxic to mammals, spiders and fish (Bossard, Randell & Hoshovsky 2000).
Compounds toxic but not necessarily lethal to rats (Connor 1977).
H
MH
Pest Animal
17. Food source to pests?Little reported to eat the plant.
L
M
18. Provides harbor?Dense foliage could provide shelter.
M
L
Agriculture
19. Impact yield?Reported to be primarily a weed of conservation areas and public amenity (Scott & Delfosse 1992).
L
H
20. Impact quality?Reported to be primarily a weed of conservation areas and public amenity (Scott & Delfosse 1992).
L
H
21. Affect land value?Reported to be primarily a weed of conservation areas and public amenity (Scott & Delfosse 1992).
L
H
22. Change land use?Reported to be primarily a weed of conservation areas and public amenity (Scott & Delfosse 1992).
L
H
23. Increase harvest costs?Reported to be primarily a weed of conservation areas and public amenity (Scott & Delfosse 1992).
L
H
24. Disease host/vector?No evidence of this reported.
L
M

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

Impact Assessment Record - Cape Ivy (PDF - 82KB)
Impact Assessment Record - Cape Ivy (DOC - 48KB)
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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