Impact Assessment - Sand rocket (Diplotaxis tenuifolia) 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 perennial herb commonly 30 to 70 cm high. It does not present a large physical barrier so would not impede individual access. It may be somewhat of a nuisance to walk through an infestation.	P & C (2001)	ML
2. Reduce tourism?	In Victoria, it is widespread in medium to large populations on coastal vegetation, lowland grassland & grassy woodland, riparian vegetation and rock outcrop vegetation. Dense patches would have a minor negative impact on aesthetics.	Carr et al (1992)	ML
3. Injurious to people?	No toxic properties.		L
4. Damage to cultural sites?	Its presence in dense patches would create a moderate negative visual impact.		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?	“In South Australia it was…sown for sand binding in pastoral country of the north east.” Not likely to contribute to soil erosion.	P & C (2001)	L
8. Reduce biomass?	“Occurs as a weed in neglected areas, roadsides, railway easements and pastures in southern Australia.” Weed replaces biomass.	P & C (2001)	ML
9. Change fire regime?	“Aerial growth dies in late autumn.” Little matter left to establish or support fire. Negligible effect on fire risk.	P & C (2001)	L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Grassy woodland (E); CMA=Port Phillip; Bioreg=Gippsland Plain; VH CLIMATE potential. Occurs in open disturbed areas (roadsides, railway easements). Can become the dominant species. Major displacement of grasses/forbs.	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
© low value EVC	Does not appear likely to invade any low value EVCs in Victoria.		L
13. Impact on structure?	“Sand rocket invades poor pastures and becomes the dominant species.” Major impact on ground covers and grasses.	P & C (2001)	ML
14. Effect on threatened flora?
Fauna
15. Effect on threatened fauna?
16. Effect on non-threatened fauna?	In some areas it is not eaten by stock except to some degree when in flower. The plant would establish successfully if fauna do not graze it. This would lead to a reduction in suitable fodder.	P & C (2001)	ML
17. Benefits fauna?	No known benefits.		H
18. Injurious to fauna?	“Claimed to be poisonous but details are lacking.” No evidence of toxicity.	P & C (2001)	L
Pest Animal
19. Food source to pests?	Not known as a food source to pests.		L
20. Provides harbour?	Growth habit of plant would not provide good cover for pest species.		L
Agriculture
21. Impact yield?	“Sand rocket invade poor pastures and becomes the dominant species. It reduces the value of fallows by depleting moisture and nutrients.” Major reduction in fodder, and potential to limit agricultural yield.	P & C (2001)	MH
22. Impact quality?	In some areas where stock does eat the plant it taints meat and dairy produce. “When occurring in cereal crops, sand rocket discolours and downgrades the harvested grain because it is green at the time of harvest.”	P & C (2001)	MH
23. Affect land value?	With the potential impact the weed can have on agricultural yields it may reduce land value somewhat.	P & C (2001)	M
24. Change land use?	In arable areas the plant can be easily controlled by deep ploughing and sowing a competitive pasture species. Not likely to affect land use.	P & C (2001)	L
25. Increase harvest costs?	“In some areas it competes with hay crops and makes cutting difficult.” Increase in time to harvest.	P & C (2001)	M
26. Disease host/vector?	None evident.		L

Impact Assessment Record - Sand rocket (PDF - 31KB)
Impact Assessment Record - Sand rocket (DOC - 58KB)
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