Impact Assessment - Pampas grass (Cortaderia selloana) in Victoria
Back | Table | Feedback
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 Pampas grass.
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: Pampas grass
Scientific name: Cortaderia selloana
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | Each tussock can grow to 6 m and several meters across, has serrated leaves and can invade riparian vegetation (Blood 2001). Dense infestations can block access to forestry plantations (Bossard, Randell & Hoshovsky 2000). Growth of pampas grass along tracks can block access (Atkinson 1997). Therefore growth of this species can result in tracks becoming impassable. | H | MH |
| 2. Reduce tourism? | Reported to impact upon the aesthetics and recreational value of invaded conservation areas in California (Bossard, Randell & Hoshovsky 2000). | H | MH |
| 3. Injurious to people? | The leaves are serrated and can cut the skin or cause irritation (Blood 2001). | MH | MH |
| 4. Damage to cultural sites? | Reported to reduce the aesthetics in some areas of California (Bossard, Randell & Hoshovsky 2000). | ML | MH |
| Abiotic | |||
| 5. Impact flow? | Not reported to occur in flowing water. | L | M |
| 6. Impact water quality? | Does occur in riparian vegetation and wetlands, no specific data reported on impact on water quality. | M | L |
| 7. Increase soil erosion? | Used historically to stabilise soil, its root system can extend radially 4 m and 3.5 m deep (Blood 2001). Therefore there is a low probability that large scale soil movement would occur in association with this species. | L | MH |
| 8. Reduce biomass? | Pampas is a large tussock forming grass that can grow to 6 m, highly invasive after disturbance, dense infestations can seriously impede overstorey regeneration (Muyt 2001). Therefore while the pampas does contribute extra biomass, it can prevent regeneration after a disturbance event and cause an overall decrease in biomass. | MH | M |
| 9. Change fire regime? | Can increase fire potential, by accumulating dry matter (Bossard, Randell & Hoshovsky 2000). Able to regrow after fire (Blood 2001). Invasion by the similar and closely related C. jubata has been shown to increase fire frequency (Lambrinos 2000). Unknown to what extent invasion by pampas can increase fire frequency or if it alters fire intensity. | M | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Creekline Grassy Woodland (E); CMA= Glenelg Hopkins ; Bioreg= Dundas Tablelands; VH CLIMATE potential. Able to exclude most other ground flora species (Muyt 2001). Therefore major displacement within layer. | MH | MH |
| (b) medium value EVC | EVC= Plains Sedgy Woodland (D); CMA= Glenelg Hopkins ; Bioreg= Dundas Tablelands; VH CLIMATE potential. Able to exclude most other ground flora species (Muyt 2001). Therefore major displacement within layer. | MH | MH |
| (c) low value EVC | EVC= Wet Heathland (LC); CMA= Glenelg Hopkins ; Bioreg= Glenelg Plain; VH CLIMATE potential. Able to exclude most other ground flora species (Muyt 2001). Therefore major displacement within layer. | MH | MH |
| 11. Impact on structure? | Reported to completely alter the structure of invaded communities (Blood 2001). Can exclude most other ground flora, and seriously impede overstorey regeneration (Muyt 2001). | H | MH |
| 12. Effect on threatened flora? | No specific evidence | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | No specific evidence | MH | L |
| 14. Effect on non-threatened fauna? | Reported to completely alter the structure of invaded communities (Blood 2001). Change in habitat structure and floristic composition, could impact upon food sources and available shelter and flowing on affect the composition of the fauna community. The level of impact has not however been quantified for pampas grass. | M | L |
| 15. Benefits fauna? | Used as nesting sites by long-nosed bandicoot (Chambers & Dickman 2002). | ML | H |
| 16. Injurious to fauna? | The leaves are serrated and can cut our skin and cause irritation (Blood 2001). Unknown how dangerous this would be to fauna species. | M | L |
| Pest Animal | |||
| 17. Food source to pests? | Goats will graze the species but it is not preferred (Lambert et al 1989; Pande, Kemp & Hodgson 2002). Therefore the species provides minimal food to pest species | L | MH |
| 18. Provides harbour? | Provides nest sites for European wasps and shelter for other pest animals (Blood 2001). Used as habitat by long nosed bandicoot (Chambers & Dickman 2002). Therefore it may also provide appropriate habitat for other small mammal species such as rabbits or foxes, however this is not confirmed. | M | M |
| Agriculture | |||
| 19. Impact yield? | Competes with forestry species, slowing growth and reducing establishment (Bossard, Randell & Hoshovsky 2000). After three years of growth, fertilised trees competing with pampas were approximately 100 cm shorter than the control at 450 cm, were only just more than half the diameter of approximately 80 mm of the control and were less than a quarter of the volume. Competition with pampas also resulted in a 9% mortality after 3 years compared with 0 for the control (Richardson et al 1996). Competition with pampas therefore causes a significant reduction in yield. | H | H |
| 20. Impact quality? | Unknown; it may have some impact in relation products of forestry. | M | L |
| 21. Affect land value? | Unknown; it may have some impact in relation products of forestry. | M | L |
| 22. Change land use? | Unknown; it may have some impact in relation products of forestry. | M | L |
| 23. Increase harvest costs? | Invading areas of forestry pampas can prevent access and increases the fire hazard (Bossard, Randell & Hoshovsky 2000). In New Zealand the need to manage this species has increased costs by 144% (Blood 2001). | H | MH |
| 24. Disease host/vector? | There is no evidence of this reported. | L | M |
Impact Assessment Record - Pampas grass (PDF - 63KB)
Impact Assessment Record - Pampas grass (DOC - 60KB)
This table can also be viewed as a PDF document (printer friendly). To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).
Feedback
Do you have additional information about this plant that will improve the quality of the assessment?
If so, we would value your contribution. Click on the link to go to the feedback form.
© State of Victoria (Agriculture Victoria) 1996 - .
This work, Victorian Resources Online, is licensed under a Creative Commons Attribution 4.0 licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria (Agriculture Victoria) as author, indicate if changes were made and comply with the other licence terms.
The licence does not apply to ‘branding’ or some ‘images or photographs’ that may be owned by third parties. We ask you to seek prior approval to use images using the VRO feedback form. Access to higher quality images can also be provided on request.
This page was last updated on .