Impact Assessment - Spiny rush (Juncus acutus) 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.

Question	Comments	Reference	Rating
Recreation
1. Restrict human access?	“Once firmly established, it completely covers an area and eliminates almost all other vegetation. The area also becomes impenetrable to stock and humans because of the sharp spines.”	P & C (2001)	MH
2. Reduce tourism?	“The occurrence of spiny rush along waterways can be quite important in keeping animals from water.” Similar impact in recreational areas. Potential to lead to major impact on recreation.	P & C (2001)	H
3. Injurious to people?	Both stems and leaves terminate in a sharp spine. Most stems and leaves are present all year.	P & C (2001)	MH
4. Damage to cultural sites?	Presence of the weed would create a negative visual impact.	P & C (2001)	ML
Abiotic
5. Impact flow?	“When growing in drains and watercourses, spiny rush restricts the flow of water which can result in serious flooding.”	P & C (2001)	H
6. Impact water quality?	Not known to affect water quality.		L
7. Increase soil erosion?	“In Australia it is commonly found as a weed of coastal flats, mine dumps and disturbed saline areas. When growing in drains and watercourses, spiny rush restricts the flow of water which can result in serious flooding.” Potential to cause serious flooding may lead to high probability of large scale soil movement.	P & C (2001)	H
8. Reduce biomass?	“In Australia it is commonly found as a weed of coastal flats, mine dumps and disturbed saline areas.” Biomass may increase.	P & C (2001)	L
9. Change fire regime?	Not known as a fire hazard	Randall (2001)	L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Swamp scrub (E); CMA=Corangamite; Bioreg=Warnambool Plain; VH CLIMATE potential. “…commonly found as a weed of coastal flats, mine dumps and disturbed saline areas. Eliminate almost all other vegetation.” Major displacement of grasses/ground covers.	P & C (2001)	MH
(b) medium value EVC	EVC=Plains sedgy woodland (D); CMA=Glenelg Hopkins; Bioreg=Dundas Tablelands; VH CLIMATE potential. Impact as in 10(a) above.	P & C (2001)	MH
(c) low value EVC	EVC=Coastal dune scrub (E); CMA=Port Phillip; Bioreg=Gippsland Plain; VH CLIMATE potential. Impact as in 10(a) above.	P & C (2001)	MH
11. Impact on structure?	“In Australia it is commonly found as a weed of coastal flats, mine dumps and disturbed saline areas. Once firmly established, it completely covers an area and eliminates almost all other vegetation.” Major effect on ground flora.	P & C (2001)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	“In Australia it is commonly found as a weed of coastal flats, mine dumps and disturbed saline areas.” Limited impact on fauna.	P & C (2001)	L
15. Benefits fauna?	“Spiny rush is not readily eaten by grazing animals.” No benefits	P & C (2001)	H
16. Injurious to fauna?	Not known to cause injury to fauna, however, spiny nature of plant may have potential to inflict injury should an animal attempt to browse on it. Grazing animals are not known to eat this plant; potentially minor impact.		ML
Pest Animal
17. Food source to pests?	Not known as a food source to pests.		L
18. Provides harbor?	“It also provides an effective harbour for vermin, particularly rabbits, because dogs will not work in clumps of the weed and burrows cannot be ripped.”	P & C (2001)	H
Agriculture
19. Impact yield?	No data available on agricultural impact. More commonly found in non-agricultural situations such as coastal flats, mine dumps and disturbed saline areas.		L
20. Impact quality?	As in 19 above.		L
21. Affect land value?	As in 19 above.		L
22. Change land use?	As in 19 above.		L
23. Increase harvest costs?	As in 19 above.		L
24. Disease host/vector?	No data available.		L