Impact Assessment - Devil's claw (purple flower) (Proboscidea louisianica) 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.

Question	Comments	Reference	Rating
Recreation
1. Restrict human access?	“An erect low growing annual herb 20 to 50 cm high. It occurs as isolated plants and small patches on roadsides, neglected areas and, occasionally, on fallows and in annual pastures, but broad-area infestations are rare.” The plant would have little or no impact on human traffic.	P & C (2001)	L
2. Reduce tourism?	“It is generally found on disturbed sites on roadsides and river flats.” Its presence would create a minor negative visual impact. The slimy, sticky sap exuded by the stems, and the obnoxious odour produced by the secretions on the leaves would make it unpleasant to walk through an infestation.	P & C (2001) VCPS Inc1	MH
3. Injurious to people?	No toxic properties. “Entire young pods are used for pickling.” The claws of the fruit may cause injury to the bare feet of humans.	Stevens (1994)2 P & C (2001)	ML
4. Damage to cultural sites?	Low growing annual. May present a moderate negative visual effect.	P & C (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?	It commonly grows on disturbed sites and is unlikely to contribute to soil erosion.	P & C (2001)	L
8. Reduce biomass?	Small patches of isolated plants. It would replace existing biomass.	P & C (2001)	ML
9. Change fire regime?	A low growing annual, it does not produce extensive vegetation and is unlikely to contribute to an increase in the risk of fire.	P & C (2001)	L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Plains grassy woodland (E); CMA=North Central; Bioreg=Goldfields; VH CLIMATE potential. “It occurs as isolated plants and small patches on roadsides, neglected areas and, occasionally, on fallows and in annual pastures, but broad-area infestations are rare.” Sparse population density; minor displacement of grasses/forbs.	P & C (2001)	ML
(b) medium value EVC	EVC=Riverine grassy woodland (D); CMA=Goulburn Broken; Bioreg=Murray Fans; VH CLIMATE potential. Impact as in 10(a) above.	P & C (2001)	ML
(c) low value EVC	Does not appear likely to invade in low value EVCs.		L
11. Impact on structure?	Marked seasonal variation in population size and density. Naturalised since 1882. Not documented as a weed of natural ecosystems.	P & C (2001) Carr et al (1992)	L
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	In Australia, it occurs as isolated plants in small patches. Minimal impact on the habitat of native fauna.	P & C (2001)	ML
15. Benefits fauna?	“Seeds are eaten by cockatoos.”	P & C (2001)	MH
16. Injurious to fauna?	“The fruit injures stock when caught over the mouth potentially leading to death by starvation. Also, it causes physical damage when the claws work into the animal’s body or become attached to the feet.”	P & C (2001)	H
Pest Animal
17. Food source to pests?	Seeds are eaten by cockatoos. Pest birds may also eat the seed.	P & C (2001)	ML
18. Provides harbor?	A low growing annual; unlikely to provide harbor.	P & C (2001)	L
Agriculture
19. Impact yield?	Commonly occurs as isolated plants and small patches. Is known to compete strongly with summer crops such as cotton. Minimal impact on yield. The fruit can injure stock, which may lead to death. Losses not documented.	P & C (2001)	ML
20. Impact quality?	Possible damage to sheep carcasses. Potential for major impact on quality.	P & C (2001)	MH
21. Affect land value?	Occurs as isolated plants and small patches. The plant can be easily controlled by cultivation (normal farm operation). Seed viability is low. Not likely to affect land value.	P & C (2001)	L
22. Change land use?	The plant can be easily controlled by cultivation (normal farm operation). Change in land use would not be required.	P & C (2001)	L
23. Increase harvest costs?	The dried fruit pods can break the combs of shearing machines.	P & C (2001)	M
24. Disease host/vector?	None evident		L