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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. |
Question | Comments | Rating | Confidence |
Recreation | |||
1. Restrict human access? | “Stems sprawl and root where they touch the ground, forming dense, impenetrable thickets…Serious creekline weed…Found in creeks in the Perth area” (Hussey et. al, 1997). Will impede access to waterways. | ML | H |
2. Reduce tourism? | “Stems sprawl and root where they touch the ground, forming dense, impenetrable thickets…Serious creekline weed…Found in creeks in the Perth area” (Hussey et. al, 1997). Grows to 2 m tall (anon, 2006). Tall, impenetrable would be obvious to most visitors and would reduce access to waterways for recreation. | MH | MH |
3. Injurious to people? | “Prickles few, scattered, almost straight, weak” (Dassanayake & Fosberg 1980). May cause minor damage from small prickles. | ML | H |
4. Damage to cultural sites? | “Stems sprawl and root where they touch the ground, forming dense, impenetrable thickets (Hussey et. al, 1997). Grows to 2 m tall (anon, 2006). Moderate visual effect. | ML | MH |
Abiotic | |||
5. Impact flow? | Serious creekline weed (Hussey et. al, 1997). Terrestrial species. | L | MH |
6. Impact water quality? | Serious creekline weed (Hussey et. al, 1997). Terrestrial species. | L | MH |
7. Increase soil erosion? | “Stems sprawl and root where they touch the ground, forming dense, impenetrable thickets…Serious creekline weed…Found in creeks in the Perth area” (Hussey et. al, 1997). Likely to reduce erosion by permanently binding soil over a wide area. | L | MH |
8. Reduce biomass? | No information found. | M | L |
9. Change fire regime? | No information found. | M | L |
Community Habitat | |||
10. Impact on composition (a) high value EVC | EVC=Cool Temperate Rainforest (V); CMA=Corangamite; Bioreg=Otway Ranges; CLIMATE=VH. No information found. | M | L |
(b) medium value EVC | EVC=Warm Temperate Rainforest (R); CMA=West Gippsland; Bioreg=Wilsons Promontory; CLIMATE=VH. No information found. | M | L |
(c) low value EVC | EVC=Damp Forest (LC); CMA=West Gippsland; Bioreg=Wilsons Promontory; CLIMATE=VH. No information found. | M | L |
11. Impact on structure? | No information found. | M | L |
12. Effect on threatened flora? | No information found. | MH | L |
Fauna | |||
13. Effect on threatened fauna? | No information found. | MH | L |
14. Effect on non-threatened fauna? | No information found. | M | L |
15. Benefits fauna? | No information found. | M | L |
16. Injurious to fauna? | “Prickles few, scattered, almost straight, weak” (Dassanayake & Fosberg 1980). May cause minor damage from small prickles. | MH | MH |
Pest Animal | |||
17. Food source to pests? | “New plants are spread from seeds carried by birds and foxes” (Hussey et. al, 1997). | MH | MH |
18. Provides harbor? | No information found. | M | L |
Agriculture | |||
19. Impact yield? | No information found. | M | L |
20. Impact quality? | No information found. | M | L |
21. Affect land value? | No information found. | M | L |
22. Change land use? | No information found. | M | L |
23. Increase harvest costs? | No information found. | M | L |
24. Disease host/vector? | A fungal disease of tea plants has been recorded on this plant, described as a minor root rot in South India (AFFA, 2004). | MH | MH |