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Impact Assessment - Cabomba (Cabomba caroliniana) 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.

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 Cabomba

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 - 1026 KB)
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: Cabomba
Scientific name: Cabomba caroliniana

Question
Comments
Rating
Confidence
Recreation
1. Restrict human access?Aquatic species (Panetta, et al 1998). Access to recreational areas not affected.
L
H
2. Reduce tourism?As a potentially invasive aquatic weed, water-based recreations may be seriously affected. “…water skiers or swimmers could easily become entangled by the weed’s long thick stems and drown” (Panetta, et al 1998).
H
MH
3. Injurious to people?No known toxic principles.
L
MH
4. Damage to cultural sites?Moderate negative visual effect.
ML
MH
Abiotic
5. Impact flow?Cabomba could grow in irrigation channels, “…where it could impede water flow, cause overflows and blockages” (Panetta, et al 1998). Serious impact on flow.
H
MH
6. Impact water quality?“Oxygen depletion can occur when massive dieback and consequent decomposition occurs. In Queensland, cabomba infestations may deleteriously affect water quality through increasing water colour” (Panetta, et al 1998). High effect on dissolved O2 levels.
H
MH
7. Increase soil erosion?“Cabomba is found in ponds, ditches, small shallow lakes and slow flowing streams. If present in water storages, heavy infestations, because of the large volume of plant material, could cause water loss from overflow or seepage” (Panetta, et al 1998). Although water flow may not be significant, overflows may create some minor soil erosion,..
ML
MH
8. Reduce biomass?“Cabomba is capable of rapid spread once it has been introduced in to a suitable water body. It was first reported from Lake MacDonald in April 1992, and by 1995 had invaded almost the whole of the lake’s extensive littoral zone” (Panetta, et al 1998). As an aquatic species, the significant increase in biomass is a negative attribute.
H
MH
9. Change fire regime?Aquatic species.
L
MH
Community Habitat
10. Impact on composition
(a) high value EVC
Basin=Snowy River- Brodribb River (ISC=excellent); CMA=East Gippsland; CLIMATE=VH.
“It is extremely persistent and can establish a monoculture by excluding native plant species” (ARMCANZ 2000). Monoculture within a specific layer.
H
MH
(b) medium value EVCAquatic species. All Victorian water bodies considered to comprise high value EVCs only (Weiss pers. coms.)i.
L
H
(c) low value EVCAquatic species. All Victorian water bodies considered to comprise high value EVCs only (Weiss pers. coms.)ii.
L
H
11. Impact on structure?“It is extremely persistent and can establish a monoculture by excluding native plant species” (ARMCANZ 2000).
H
MH
12. Effect on threatened flora?This species is not documented as posing an additional risk to threatened flora.
MH
L
Fauna
13. Effect on threatened fauna?This species is not documented as posing an additional risk to threatened fauna.
MH
L
14. Effect on non-threatened fauna?“Its ability to replace native aquatic plants, with the likely displacement of native fish and invertebrate populations, together with the ability to infest large areas of water, suggest that native aquatic life would be considerably endangered” (Panetta, et al 1998). Reduction in habitat leading to reduced populations.
MH
MH
15. Benefits fauna?“In regions where it is invasive, it is not clear whether native fish and invertebrates utilize it readily as a habitat” (Panetta, et al 1998). Assume limited or no benefits.
M
MH
16. Injurious to fauna?Not known to be injurious.
L
MH
Pest Animal
17. Food source to pests?Aquatic species (P & C 2001).
L
MH
18. Provides harbor?Aquatic species (P & C 2001).
L
MH
Agriculture
19. Impact yield?No evidence. Not known as a weed of agriculture. It can occur in irrigation systems and demonstrate allelopathy on seed germination in wheat and lettuce (P & C 2001). Potential to affect irrigated crops. Impact unknown.
ML
MH
20. Impact quality?Not a weed of agriculture.
L
MH
21. Affect land value?Not a weed of agriculture.
L
MH
22. Change land use?Not a weed of agriculture.
L
MH
23. Increase harvest costs?Not a weed of agriculture.
L
MH
24. Disease host/vector?None evident
L
MH

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

Impact Assessment Record - Cabomba (PDF - 68KB)
Impact Assessment Record - Cabomba (DOC - 55KB)
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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