Impact Assessment - Mirror-bush (Coprosma repens) 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 Mirror-bush
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: Mirror-bush
Scientific name: Coprosma repens
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | Densely growing shrub to small tree, serious weed in coastal areas that can completely smother all other vegetation (Blood 2001), and is capable of forming dense colonies (DPIWE 2001). Likely to restrict access to some degree, but no specific reference was found. | M | M |
| 2. Reduce tourism? | Densely growing shrub to small tree, serious weed in coastal areas that can completely smother all other vegetation (Blood 2001), occurring in widespread medium to large populations (Carr et al 1992). Not described as impacting on recreational use, but likely to have a minor negative affect on the aesthetics of an area. | ML | MH |
| 3. Injurious to people? | Not described as possessing any properties injurious to people. | L | M |
| 4. Damage to cultural sites? | Has been observed germinating and establishing in brickwork (B. Mitchard pers. com.). Could have a structural impact but this is not confirmed. | M | M |
| Abiotic | |||
| 5. Impact flow? | Not described as establishing in flowing water or riparian environments (Carr et al 1992), so is unlikely to impact on water flow. | L | MH |
| 6. Impact water quality? | Not described as establishing in flowing water or riparian environments (Carr et al 1992), so is unlikely to impact on water flow. | L | M |
| 7. Increase soil erosion? | Described as a plant suitable for sand bank restoration and slope stabilisation (NZERN 2001). Potential to decrease the probability of soil erosion. | L | M |
| 8. Reduce biomass? | ‘…impedes the growth and regeneration of indigenous overstorey species Muyt 2001)’. It could slightly decrease the long term biomass of a community by suppressing larger woody species. | MH | MH |
| 9. Change fire regime? | Described as a plant that is ‘hard to burn’ (NSW RFS) and therefore because it invades ecosystems such as heathland, (Carr et al 1992) which are adapted to fire (Groves 1994), it could reduce fire intensity, and maybe also frequency in these ecosystems. However, the level of impact is not clear. | M | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Coast Banksia Woodland (BCS= E); CMA= West Gippsland; Bioreg= Strzelecki Ranges; CLIMATE potential=VH. ‘Canopy of mature plant will completely smother all other vegetation (Blood 2001)’. ‘…capable of forming dense colonies in native bushland, displacing native flora and fauna (DPIWE 2001)’. Potential to form monoculture; displacing all species within a strata/layer. | H | MH |
| (b) medium value EVC | EVC= Coastal Headland Scrub (BCS= D); CMA= West Gippsland; Bioreg= Gippsland Plain; CLIMATE potential=VH. ‘Canopy of mature plant will completely smother all other vegetation (Blood 2001)’. ‘…capable of forming dense colonies in native bushland, displacing native flora and fauna (DPIWE 2001)’. Potential to form monoculture; displacing all species within a strata/layer. | H | MH |
| (c) low value EVC | EVC= Heathy Woodland (BCS= LC); CMA= Corangamite; Bioreg= Otway Plain; CLIMATE potential=VH ‘Canopy of mature plant will completely smother all other vegetation (Blood 2001)’. ‘…capable of forming dense colonies in native bushland, displacing native flora and fauna (DPIWE 2001)’. Potential to form monoculture; displacing all species within a strata/layer. | H | MH |
| 11. Impact on structure? | ‘Canopy of mature plant will completely smother all other vegetation (Blood 2001)’. Capable of forming dense colonies in native bushland (DPIWE 2001) and impedes the growth and regeneration of indigenous overstorey species (Muyt 2001). In certain communities such as heathland, could have major effect on all layers forming monoculture. | H | MH |
| 12. Effect on threatened flora? | Described as a ‘significant weed’ in Coastal Moonah Woodland that is listed as a threatened community under the FFG Act 1988 (Turner & Tonkinson 2003). However, its impact on specific threatened species was not found described. | MH | M |
| Fauna | |||
| 13. Effect on threatened fauna? | Described as a ‘significant weed’ in Coastal Moonah Woodland, listed as a threatened community under the FFG Act 1988 (Turner & Tonkinson 2003). ‘…capable of forming dense colonies in native bushland, displacing native flora and fauna (DPIWE 2001)’. Potential to also impact on threatened fauna, though not specifically documented. | MH | ML |
| 14. Effect on non-threatened fauna? | ‘…capable of forming dense colonies in native bushland, displacing native flora and fauna (DPIWE 2001)’. Reduction in habitat for fauna leading to a reduction in numbers of individuals. | MH | M |
| 15. Benefits fauna? | Consumed by birds, including the Silver gull (Carr et al 1993), and possibly possums (Muyt 2001). In New Zealand described as a food source for lizards (Whittaker 1987). Likely to provide some assistance as a food source to desirable species. | MH | MH |
| 16. Injurious to fauna? | Not found documented as possessing any properties injurious to fauna. | L | M |
| Pest Animal | |||
| 17. Food source to pests? | Seed possibly dispersed by foxes (Muyt 2001). Potential to provide food to one serious pest. | MH | MH |
| 18. Provides harbour? | As a densely growing shrub/tree (Blood 2001), capable of forming dense colonies (DPIWE 2001) it has the capacity to provide harbour to serious pests such as rabbits or foxes, however, nothing was specifically described. | M | M |
| Agriculture | |||
| 19. Impact yield? | Not described as a weed of agriculture. | L | M |
| 20. Impact quality? | Not described as a weed of agriculture. | L | M |
| 21. Affect land value? | Not described as a weed of agriculture. | L | M |
| 22. Change land use? | Not described as a weed of agriculture. | L | M |
| 23. Increase harvest costs? | Not described as a weed of agriculture. | L | M |
| 24. Disease host/vector? | Not described as a weed of agriculture. | L | M |
Impact Assessment Record - Mirror-bush (PDF - 89KB)
Impact Assessment Record - Mirror-bush (DOC - 60KB)
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