Impact Assessment - Abrojo (chain-link cactus, sheathed cholla) (Cylindropuntia tunicata) 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 Abrojo (chain-link cactus, sheathed cholla).
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: Abrojo (chain-link cactus, sheathed cholla).
Scientific name: Cylindropuntia tunicata
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | ‘If uncontrolled the plant can also form relatively dense infestations that are unsafe for an animal to walk through’ (WSC 2004). Has ‘numerous, long, tough, sharp, sheathed spines, which can penetrate leather boots, vehicle tyres and animals’ and is difficult to control (Laity 2005). Grows to 60 cm (Britton & Rose 1919). Therefore would be of high nuisance value to people and due to the potential of puncturing tyres a major impediment to vehicles. | H | MH |
| 2. Reduce tourism? | The species is mat forming cactus recorded in Eucalypt woodland (Hosking, Conn & Lepschi 2006). Spines can penetrate boots and vehicle tyres (Laity 2005). The species could therefore affect some recreational activities such as bush walking of 4W Driving. | MH | M |
| 3. Injurious to people? | The species has spines that can be from 3-6 cm long (FNA 2007). Spines can penetrate boots and vehicle tyres (Laity 2005). | H | MH |
| 4. Damage to cultural sites? | Unlikely to cause structural damage the species could have some impact on the aesthetics of an area. This has not however been reported. | ML | L |
| Abiotic | |||
| 5. Impact flow? | Terrestrial species. | L | MH |
| 6. Impact water quality? | Terrestrial species. | L | MH |
| 7. Increase soil erosion? | Many of the Cylindropuntia spp. have fibrous root systems (Britton & Rose 1919). Unlikely to contribute to large scale soil movement. | L | MH |
| 8. Reduce biomass? | The species is a mat forming cactus which if left uncontrolled can form relatively dense infestations (Hosking, Conn & Lepschi 2006; WSC 2004). Therefore if the species invades a relatively open habitat as it is reported to do it is likely to cause an increase in biomass. | L | MH |
| 9. Change fire regime? | Due to the higher moisture content of succulents and therefore the decreases flammability of the plant tissue Invasion by Opuntia spp. may decrease fire frequency and intensity, however this has not been fully proven (Brooks et al 2004). | ML | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= semi-arid woodland (V); CMA=Mallee; Bioregion= Murray Mallee; CLIMATE potential=VH. ‘Bushy or mat-forming and creeping’ (Benson 1982). ‘If uncontrolled the plant can also form relatively dense infestations’ (WSC 2004). Minor displacement of some dominant species within the lower layer. | ML | M |
| (b) medium value EVC | EVC= semi-arid woodland (D); CMA=Mallee; Bioregion= Lowan Mallee; CLIMATE potential=VH. ‘Bushy or mat-forming and creeping’ (Benson 1982). ‘If uncontrolled the plant can also form relatively dense infestations’ (WSC 2004). Minor displacement of some dominant species within the lower layer. | ML | M |
| (c) low value EVC | EVC= lowan sands mallee (LC); CMA=Mallee; Bioregion= Lowan Mallee; CLIMATE potential=VH. ‘Bushy or mat-forming and creeping’ (Benson 1982). ‘If uncontrolled the plant can also form relatively dense infestations’ (WSC 2004). Minor displacement of some dominant species within the lower layer. | ML | M |
| 11. Impact on structure? | Tends to be found in grasslands or very open woodlands. ‘Bushy or mat-forming and creeping’ (Benson 1982). ‘If uncontrolled the plant can also form relatively dense infestations’ (WSC 2004). Minor effect on lower 20 – 60% of ground layer. | ML | M |
| 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? | Unknown. | MH | L |
| 14. Effect on non-threatened fauna? | Unknown. | M | L |
| 15. Benefits fauna? | Weed not documented to provide benefits to desirable species. | H | M |
| 16. Injurious to fauna? | ‘Their spines readily penetrate the flesh of domestic grazing animals, thereby harming the animal’ (WSC 2004). Likely that the weed could also affect indigenous fauna. Large spines dangerous to fauna. | H | M |
| Pest Animal | |||
| 17. Food source to pests? | The similar species C. imbracata is reported to be eaten by rabbits and rodents in the US especially during times of drought (Bunting & Wright 1976). Therefore C. tunicata may provide some food to pest species. | M | M |
| 18. Provides harbor? | The species is not reported to provide shelter to pest species, as it is a mat forming cactus with large spines it could have the potential to do so (Hosking, Conn & Lepschi 2006). | M | L |
| Agriculture | |||
| 19. Impact yield? | Unknown; due to the species spines and matt forming nature, like other Opuntia species it may restrict grazing animals and therefore reduce the effective area of production (Hosking, Conn & Lepschi 2006; Pierper 1971). | M | L |
| 20. Impact quality? | Unknown; However, other similar Cylindropuntia species have been reported to reduce the quality of wool (Pierper 1971). | M | L |
| 21. Affect land value? | O. aurantiaca infestations ‘seriously inhibit pastoral activities and result in a marked devaluation in the price of infested land’ ‘Control can be very costly’ (Stirton 1978). Possible that C. tunicata could have a similar impact but no documented evidence. | M | L |
| 22. Change land use? | O. aurantiaca infestations ‘seriously inhibit pastoral activities and result in a marked devaluation in the price of infested land’ ‘Control can be very costly’ (Stirton 1978). Possible that C. tunicata could cause a change in priority of land use but no documented evidence. | M | L |
| 23. Increase harvest costs? | Their spines readily penetrate the flesh of domestic grazing animals, thereby harming the animal’ (WSC 2004). The species spines can penetrate tyres (Laity 2005). Therefore extra care would need to be taken with stock near populations increasing time or labour and the damage the species could cause to tyres may increase maintenance costs.. | M | M |
| 24. Disease host/vector? | Other Opunita species are reported as a host of Fruit fly (Blood 2001). | M | L |
This table can also be viewed as a PDF document (printer friendly).
Impact Assessment Record - Abrojo (chain-link cactus, sheathed colla) (PDF - 55 KB)
Impact Assessment Record - Abrojo (chain-link cactus, sheathed colla) (DOC - 44 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).
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