Impact Assessment - Fennel (Foeniculum vulgare) 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 multi-stemmed perennial herb commonly 1.5 to 2.0 metres high. It is found along waterways, drainage lines and in seasonally moist locations within grasslands and woodlands. Dense infestations may restrict access to waterways. A soft, herbaceous plant the high growth of the plant may be a nuisance to people.	Muyt (2001)	ML
2. Reduce tourism?	Dense infestations along waterways may restrict some recreational activities.	Muyt (2001)	MH
3. Injurious to people?	The National Occupational Health and Safety Commission documents F. vulgare as causing photosensitivity through skin contact with the plant or its juices.	NOHSC1	ML
4. Damage to cultural sites?	Not an aggressive root system; structure not affected. Dense infestations would create have a moderate negative visual effect.	Muyt (2001)	ML
Abiotic
5. Impact flow?	Terrestrial species.	P & C (2001)	L
6. Impact water quality?	Terrestrial species.	P & C (2001)	L
7. Increase soil erosion?	A perennial herb that in dense infestations eliminates most other ground flora, but retains good ground cover. It has a stout branched taproot to around 1 metre deep with many laterals. Not likely to contribute to soil erosion.	P & C (2001) Muyt (2001)	L
8. Reduce biomass?	Grows mostly in open, disturbed areas, such as roadside, railway easements, channels and drains. Minor effect on biomass. Dense infestations may increase biomass.	P & C (2001)	ML
9. Change fire regime?	Flower stems partly die back in winter. Images of dense infestations show increased dry matter. Possible minor increase to the frequency of fire risk.	P & C (2001) TNC2	ML
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Plains grassland (E); CMA=West Gippsland; Bioreg=Highlands – Southern Falls; VH CLIMATE potential “Grows best in open, unshaded situations. Once established, fennel excludes almost all other vegetation.” Major displacement of species within different strata.	P & C (2001)	MH
(b) medium value EVC	EVC=Shrubby woodland (R); CMA=Corangamite; Bioreg=Central Victorian Uplands; VH CLIMATE potential Impact as in 10(a) above. Population density may be limited due to overstorey cover.	P & C (2001)	MH
(c) low value EVC	EVC=Heathy woodland (LC); CMA=Port Phillip; Bioreg=Gippsland Plain; VH CLIMATE potential Impact as in 10(b) above.	P & C (2001)	MH
11. Impact on structure?	“Dense infestations eliminate most other ground-flora and severely impede overstorey regeneration.” Major effect on ground flora.	Muyt (2001)	ML
12. Effect on threatened flora?12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	While livestock may find the plant palatable, its widespread distribution in medium to large populations suggests that native fauna do not significantly graze on it. With its dominant nature, it is likely to reduce habitat.	CEPPC3 Carr et al (1992)	MH
15. Benefits fauna?	No documented benefits.		H
16. Injurious to fauna?	“Apparently animals graze the fennel stubble without ill effects.” Not known to cause injury to native fauna.	P & C (2001)	L
Pest Animal
17. Food source to pests?	No evidence of the plant providing food to pest species.		L
18. Provides harbor?	Dense infestations may provide harbor for minor pests such as rodents.		L
Agriculture
19. Impact yield?	Not a serious weed of pasture or cropping. “It does not establish in grazed pastures or cultivated paddocks. Herb growers note that tomatoes and beans do not grow in association with fennel, suggesting possible allelopathic effect.” Likely to have some effect in those situations.	P & C (2001)	ML
20. Impact quality?	Not a serious weed of pasture or cropping. “When growing on headlands of arable crops, seedlings often occur in the crops.” Minor impact on quality through seed contamination.	P & C (2001)	ML
21. Affect land value?	Not a serious weed of pasture or cropping. Not likely to affect land value.	P & C (2001)	L
22. Change land use?	Not a serious weed of pasture or cropping. Land use not affected.	P & C (2001)	L
23. Increase harvest costs?	No increase in harvest costs.		L
24. Disease host/vector?	None evident.		L