Impact Assessment - Tufted honeyflower (Melianthus comosus) 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?	“An erect, much branched shrub, commonly 1.2 to 2 m high. Very dense clumps which restrict animal movement develop.” People would access areas with difficulty.	P & C (2001)	MH
2. Reduce tourism?	Limited distribution in Victoria. Population sizes not documented, but the plant is known to grow in watercourses. As the plant has the ability to form very dense clumps, at least some water-based recreational activities may be affected.	P & C (2001)	MH
3. Injurious to people?	“…all parts of the plant are toxic.”	P & C (2001)	H
4. Damage to cultural sites?	Dense patches would create a negative visual effect.		ML
Abiotic
5. Impact flow?	Terrestrial species, however, the plant is known to grow in watercourses and, “…can divert streams.” Possible major impact on waterflow in streams.	P & C (2001)	MH
6. Impact water quality?	Not known to affect water quality.		L
7. Increase soil erosion?	The root system is woody, rather shallow but extensive. Can form dense clumps; not likely to increase soil erosion.	P & C (2001)	L
8. Reduce biomass?	Plants are evergreen and can grow to a maximum height of 2.5 metres. Biomass likely to increase.	P & C (2001)	L
9. Change fire regime?	Not data available on flammability. As an evergreen shrub it may not support fire very well. Not likely to change the risk of fire.		L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Swamp scrub (E); CMA=North Central; Bioreg=Goldfields; VH CLIMATE potential. Forms dense stands. Grows in full sun or part shade. Dense stands can eliminate all other species. Monoculture.	Blood (2001) P & C (2001)	H
(b) medium value EVC	EVC=Riverine grassy woodland (D); CMA=Goulburn Broken; Bioreg=Murray Fans; VH CLIMATE potential. Impact as in 10(a) above.	Blood (2001) P & C (2001)	H
(c) low value EVC	Does not occur in any low value EVCs.		L
11. Impact on structure?	“Infestations of tufted honey flower may become so dense that they eliminate all other species.” Usually confined to open areas. Affects ground flora, possibly some shrubs.	P & C (2001)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	“Although all parts are toxic, the objectionable odour deters grazing animals and the plant is rarely eaten. Very dense clumps which restrict animal movement and reduce pasture production, develop.” Reduces available fodder for fauna species.	P & C (2001)	ML
15. Benefits fauna?	No known benefits.		H
16. Injurious to fauna?	“All parts of the plant are toxic. Drenching trials show that death occurs within about 4 hours of ingestion.” However, the plant is rarely eaten due to the objectionable odour it produces.	P & C (2001)	ML
Pest Animal
17. Food source to pests?	Not known as a food source to pests.		L
18. Provides harbor?	“Very dense clumps…provide harbour for pest animals.”	P & C (2001)	H
Agriculture
19. Impact yield?	“Although all parts are toxic, the objectionable odour deters grazing animals and the plant is rarely eaten. Very dense clumps which restrict animal movement and reduce pasture production, develop.” Reduced pasture and possible animal losses; potentially major impact on quantity.	P & C (2001)	MH
20. Impact quality?	Not known to affect cropping or to contaminate agricultural produce.		L
21. Affect land value?	It only occurs in a few areas of southern Australia. Minimal effect on land value.	P & C (2001)	L
22. Change land use?	“Although all parts are toxic, the objectionable odour deters grazing animals and the plant is rarely eaten.” And, it only occurs in a few areas of southern Australia. Change in land use not required.		L
23. Increase harvest costs?	Not a weed of cropping. Does not affect harvest costs.		L
24. Disease host/vector?	None evident.		L

Impact Assessment Record - Tufted honeyflower (PDF - 31KB)
Impact Assessment Record - Tufted honeyflower (DOC - 59KB)
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