Impact Assessment - Apple of Sodom (Solanum linnaeanum) 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?	S. linnaeanum grows well in sandy coastal areas where it strongly competes with native species. If left to develop it can, “…result in dense patches which crowd out other vegetation [and] restrict stock movement.” Because of its prickly nature it may potentially restrict human access.	P & C (2001)	ML
2. Reduce tourism?	In Victoria, its distribution is limited, but it occurs in medium to large populations. Because of its prickly nature, its presence may affect some recreational activities, particularly bushwalking or hiking.	Carr et al (1992) P & C (2001)	MH
3. Injurious to people?	An erect perennial shrub, the plant has numerous prickles on the stem, leaves and fruit. The fruit is poisonous.	P & C (2001)	H
4. Damage to cultural sites?	Dense patches may create a negative visual effect.		ML
Abiotic
5. Impact flow?	Terrestrial sp.	P & C (2001)	L
6. Impact water quality?	Terrestrial sp.	P & C (2001)	L
7. Increase soil erosion?	A perennial, spreading shrub with a stout taproot. Plants are partially deciduous in winter. Not likely to increase soil erosion.	P & C (2001)	L
8. Reduce biomass?	It competes strongly with native plants and crowds out other vegetation. Direct replacement of biomass.	P & C (2001)	ML
9. Change fire regime?	Predominantly evergreen (plants are partially deciduous), it does not significantly increase fuel load. It therefore presents little change to the fire regime.	P & C (2001)	L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Coastal dune scrub (E); CMA=Glenelg Hopkins; Bioreg=Warnambool Plain; VH CLIMATE potential Occurs in medium to large populations and, “…competes strongly with native species.” Major displacement of grasses/forbs.	Carr et al (1992) P & C (2001)	MH
(b) medium value EVC	EVC=Coastal dune scrub (D); CMA=Glenelg Hopkins; Bioreg=Victorian Volcanic Plain; VH CLIMATE potential. Occurs in medium to large populations and, “…competes strongly with native species.” Impact as above..	Carr et al (1992) P & C (2001)	MH
(c) low value EVC	EVC=Heathy woodland (E); CMA=Corangamite; Bioreg=Otway Plains; VH CLIMATE potential “Grows well…[in]…coastal areas.” Prefers open areas. Possible minor impact in woodland areas.	P & C (2001)	ML
11. Impact on structure?	“Dense patches can crowd out other vegetation.” It also, “…competes strongly with native species.” It would have a major impact on the floral strata in coastal vegetation and grasslands.	P & C (2001) Carr et al (1992)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	Medium to large populations, though limited in distribution. Competes with beneficial plants so is likely to reduce food source for non-threatened fauna. Spiny nature of plant discourages grazing.	Carr et al (1992) P & C (2001)	ML
15. Benefits fauna?	No benefits for fauna. “Neither the fruit nor seeds are eaten by birds or animals.”	P & C (2001)	H
16. Injurious to fauna?	Prickles present throughout the year. Fruit is poisonous.	P & C (2001)	H
Pest Animal
17. Food source to pests?	“Neither the fruit nor seeds are eaten by birds or animals.”	P & C (2001)	L
18. Provides harbor?	The plant does provide harbor for rabbits. As a perennial, it possibly provides for permanent harbor.	P & C (2001)	H
Agriculture
19. Impact yield?	Although the fruit is poisonous, animals avoid grazing the plant because of its prickly nature. Infestations crowd out other vegetation and restricts stock movement; reduces carrying capacity.	P & C (2001)	ML
20. Impact quality?	Seeds do not present as impurities in seed or cereal crops. No burrs to affect wool.	P & C (2001)	L
21. Affect land value?	It is more a problem in unimproved pastures. Would have minimal impact on land value.	P & C (2001)	L
22. Change land use?	It is more a problem in unimproved pastures. Seedlings are easily killed by frequent cultivation as part of crop sowing or pasture improvement.	P & C (2001)	L
23. Increase harvest costs?	No evidence of increased harvest costs.		L
24. Disease host/vector?	None evident.		L