Impact Assessment - Bridal creeper (Western Cape form) (Asparagus asparagoides) 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 Bridal creeper (Western Cape form).
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: Bridal creeper (Western Cape form)
Scientific name: Asparagus asparagoides
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | WCF supposedly not meant to grow in saline conditions, but found thriving on sand dunes adjacent to SA beaches (Hay ’07). Perennial climber that dominates ground flora, and can form “dense curtains smothering shrubs and the lower canopy of trees” (Muyt, ’01). Whilst the plant does occur in riparian areas, it is most vigorous on lighter well-drained soils. Its presence proves a nuisance value to humans, impeding individual access to waterways and walking tracks. | ML | M |
| 2. Reduce tourism? | Perennial climber that dominates ground flora, and can form “dense curtains smothering shrubs and the lower canopy of trees” (Muyt, ’01; Holland Clift, ‘05). The smothering curtains that this species creates would present a major negative impact on aesthetics. | MH | M |
| 3. Injurious to people? | This species seemingly presents no harmful or toxic properties to humans. | L | M |
| 4. Damage to cultural sites? | No specific mention of damage to cultural sites found in literature reviewed. However, as WCF grows prolifically in coastal areas (Hay, ’07; Kleinjan, et al., ‘99) where Aboriginal middens are present, the reviewer has no hesitation in assuming that it has the potential to obscure, if not smother, sites of significance. It has also been mentioned that WCF can grow over and smother trees and small buildings, therefore Aboriginal scar trees, cemetery plots, and other sites of significance MAY be at risk. (NB. Cemeteries were mentioned as ‘at risk’ by smothering by bridal veil and the common form of bridal creeper; the extrapolation to WCF seemed quite acceptable.) Assumption of potential to cause major structural and/or visual effect to culturally significant sites, that MAY adversely affect the heritage/cultural feature. | H | ML |
| Abiotic | |||
| 5. Impact flow? | WCF is a terrestrial species. It has not been found growing within waterbodies, although it is very vigorous in riparian areas. According to many sources, including Muyt (2001), “… It is usually most vigorous on lighter, well-drained soils.” It MAY reduce the volume of runoff in riparian areas where it is growing rampantly. WCF appears to have little, or negligible, effect on water flow within waterbodies. | L | L |
| 6. Impact water quality? | WCF is a terrestrial species. WCF has no noticeable effect on dissolved O2, or light levels, within waterbodies. | L | L |
| 7. Increase soil erosion? | WCF is a terrestrial species. It has not been found growing within waterbodies, although it is very vigorous in riparian areas. According to many sources, including Muyt (2001), “… It is usually most vigorous on lighter, well-drained soils.” WCF MAY temporarily aid in bank stabilisation whilst it is smothering undergrowth and impeding the access to river banks by visitors; however, as it kills the substrate it MAY leave the bank less stable than prior to its infestation. Low probability of large scale soil movement. | L | L |
| 8. Reduce biomass? | It smothers pre-existing vegetation and prevents other plants from growing. (Holland Clift, ’05). Biomass may increase. | L | L |
| 9. Change fire regime? | Dead and dry matter may significantly add to the fuel load, which in turn may increase the intensity of a local fire. NB. “Bridal creeper (inc. WCF) is often the first plant to emerge post-fire, therefore herbicides can be carefully applied before native plants regenerate.” NAWMC (2006). Minor change to the intensity of fire risk. | ML | ML |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC = Coastal Headland Scrub (V); CMA = Glenelg Hopkins; Bioregion = Bridgewater; VH CLIMATE potential. Predictive mapping shows that it can potentially grow along all Australian coastlines with a Mediterranean climate. It smothers pre-existing vegetation and prevents other plants from growing. (Holland Clift, ’05). Monoculture within a specific layer; displaces all spp. within a strata/layer. | H | M |
| (b) medium value EVC | EVC = Coastal Dune Scrub/Coastal Dune Grassland Mosaic (D); CMA = Corangamite; Bioregion = Victorian Volcanic Plain; VH CLIMATE potential. Predictive mapping shows that it can potentially grow along all Australian coastlines with a Mediterranean climate. It smothers pre-existing vegetation and prevents other plants from growing. (Holland Clift, ’05). Monoculture within a specific layer; displaces all spp. within a strata/layer. | H | M |
| (c) low value EVC | EVC = Coastal Alkaline Scrub (LC); CMA = Glenelg Hopkins; Bioregion = Bridgewater; VH CLIMATE potential. Predictive mapping shows that it can potentially grow along all Australian coastlines with a Mediterranean climate. It smothers pre-existing vegetation and prevents other plants from growing. (Holland Clift, ’05). Monoculture within a specific layer; displaces all spp. within a strata/layer. Monoculture within a specific layer; displaces all spp. within a strata/layer. Monoculture within a specific layer; displaces all spp. within a strata/layer. | H | M |
| 11. Impact on structure? | It smothers pre-existing vegetation and prevents other plants from growing. (Holland Clift, ’05) The tubers act as a barrier to impede the root growth of other plants, and often prevents their seedling establishment (NAWMC, ’06). Major effects on all layers. Forms monoculture. | H | M |
| 12. Effect on threatened flora? | As WCF’s habit often results in smothering of all flora in its way, any floral VROT species in its way MAY also be smothered, resulting in localised reductions in populations that may be significant. Although no such records could be found by the assessor at this time, this does not exclude it from the realm of probability within any vegetation communities that occur within WCF’s preferred habitats. WCF forms monoculture in preferred habitats. | H | L |
| Fauna | |||
| 13. Effect on threatened fauna? | As WCF’s habit often results in smothering of all flora in its way, any floral VROT species in its way MAY also be smothered, resulting in localised reductions in populations that may be significant food sources to local fauna (inc. faunal VROT). This MAY lead to local extinctions, reduction of local numbers of individuals, or local reduction in habitat for threatened species. Although no such records could be found by the assessor at this time, this does not exclude it from the realm of probability within any bio-communities that occur within WCF’s preferred habitats. Reduction in habitat for threatened species, leading to reduction in local numbers of individuals, OR maybe local extinctions. | MH | L |
| 14. Effect on non-threatened fauna? | As WCF’s habit often results in smothering of all flora in its way, resulting in localised reductions in populations that may be significant food sources to local fauna. This MAY lead to local extinctions, reduction of local numbers of individuals, or local reduction in habitat for threatened species. Although no such records could be found by the assessor at this time, this does not exclude it from the realm of probability within any bio-communities that occur within WCF’s preferred habitats. Reduction in habitat for threatened species, leading to reduction in local numbers of individuals, OR maybe local extinctions. | MH | L |
| 15. Benefits fauna? | Some bird species, Zosterops lateralis (Silvereye) and Corvus bennetti (Little Crow) are known to feed on the fruit. (Stansbury, ’96). WCF provides some food to desirable species. | MH | MH |
| 16. Injurious to fauna? | No documented adverse effects to fauna found in literature reviewed. | L | M |
| Pest Animal | |||
| 17. Food source to pests? | Bird species, both native and introduced, are known to feed on the fruit. “… the introduced starling were identified as feeding on bridal creeper fruits in South Australia.” (Stansbury, ’96). Potential to supply food to one, or more, minor pest species. | ML | MH |
| 18. Provides harbor? | The dense growth, which occurs in late winter, may provide some temporary harbour, particularly for birds. No documented harbour for pest animals found in literature reviewed. | L | L |
| Agriculture | |||
| 19. Impact yield? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to reduce fruit production (Ibid.). [Amount unknown.] Minor impact on quantity of produce (e.g. ~ 10% assumed, if it was significant assume amount stated). | M | M |
| 20. Impact quality? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to reduce air movement, increasing local humidity, leading to Septoria spot on fruit (Ibid.). [Amount unknown.] Impact on quality of produce (~ 10%). | M | M |
| 21. Affect land value? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to reduce fruit production and quality [amount unknown.], thus reducing the value on land used for citrus orchards (Ibid.). Decreases in land value ~ 10%. | M | M |
| 22. Change land use? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to reduce fruit production and quality [amount unknown.], thus reducing the value on land used for citrus orchards leading to a change in land use (Ibid.). Downgrading of the priority land use. | MH | M |
| 23. Increase harvest costs? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to leave a large volume of dead stems reducing the ease of access whilst harvesting fruit (Ibid.). [Amount unknown.] Minor increase in cost of harvesting. | M | M |
| 24. Disease host/vector? | Adversely affects pine plantations (Blood, ’01) and citrus orchards (Ibid, Kwong et al. ’02). In citrus, bridal creeper infestation is known to leave a large volume of dead stems that serve as a disease reservoir for reinfestation of Septoria spot on fruit (Ibid.). [Amount unknown.] Host to severe disease of citrus. | H | M |
This table can also be viewed as a PDF document (printer friendly).
Impact Assessment Record - Bridal creeper (PDF - 125KB)
Impact Assessment Record - Bridal creeper (DOC - 67KB)
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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