Victorian Resources Online (archived)

Impact Assessment - Ivy-leafed sida (Sida leprosa) in Victoria (Nox)

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.

Each resource attribute, or criterion, is assessed relative to a list of intensity ratings. Depending upon information found in relation to each criterion, a rating of Low, Medium Low, Medium High or High is assigned. Descriptions of the impact criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the impact of Ivy-leafed sida

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

Common Name: Ivy-Leafed sida
Scientific name: Sida leprosa (Ort.) Schum (Malvella leprosa (Ort.) Krapov.)

Question	Comments	Reference	Rating
Recreation
1. Restrict human access?	“A semi-erect perennial herb to 30 cm high.” Does not inhibit human access.	P & C (2001)	L
2. Reduce tourism?	Dense patches would be noticeable, but the low growth habit of the plant would not affect recreational activities. Minor effect to aesthetics.		ML
3. Injurious to people?	No spines or burrs. It is not known to be toxic.	P & C (2001)	L
4. Damage to cultural sites?	“…competes strongly with pasture species.” In dense patches, it may create a moderate negative visual effect.
Abiotic
5. Impact flow?	Although it occurs on “channel banks and [in] irrigated annual pastures,” it is a terrestrial species. Not known to affect water flow.	P & C (2001)	L
6. Impact water quality?	Terrestrial species.	P & C (2001)	L
7. Increase soil erosion?	A “deep-rooted perennial, [that] competes strongly with pastures species.” While aerial parts die off in autumn, the extensive root system likely to provide deeper soil binding. Moderate probability of large scale soil movement.	P & C (2001)	ML
8. Reduce biomass?	Competes strongly with pasture, particularly irrigated annual pasture. Invader replaces biomass.	P & C (2001)	ML
9. Change fire regime?	A low-growing plant, it would not add greatly to the fuel load. Small or negligible effect on fire risk.		L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Creekline grassy woodland (E); CMA=Goulburn Broken; Bioreg=Murray Fans; VH CLIMATE potential. Area of potential distribution limited. “Whilst it is well established, the areas are not large. In Victoria, it is confined to the banks of some irrigation channels. A deep-rooted perennial, it competes strongly with pasture species.” Minor impact on lower stratum.	P & C (2001)	ML
(b) medium value EVC	EVC=Riverine grassy woodland (E); CMA=Goulburn Broken; Bioreg=Murray Fans; VH CLIMATE potential. Area of potential distribution limited. Impact as in 10(a) above.	P & C (2001)	ML
(c) low value EVC	Unlikely to occur in low value EVCs in Victoria. Potential distribution limited to small areas in North Central and Goulburn Broken CMAs.		L
11. Impact on structure?	Competes strongly with pasture species. “Whilst it is well established, the areas are not large.” It would have a minor impact on the floral strata in grassland situations.	P & C (2001)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	Competes strongly with pasture species, and animals do not readily eat the plant. Infested areas are not large. Reduce food source for some native fauna.	P & C (2001)	ML
15. Benefits fauna?	No benefits.	P & C (2001)	H
16. Injurious to fauna?	Not known to be toxic.		L
Pest Animal
17. Food source to pests?	Not known as a food source to pest animals.		L
18. Provides harbour?	Low-growing plant with annual vegetation. Not likely to provide harbour.	P & C (2001)	L
Agriculture
19. Impact yield?	“Competes strongly with pasture species…[and] it is not readily eaten by animals.” However, infested areas are not large. Likely to have minor impact on yield.	P & C (2001)	ML
20. Impact quality?	Not known as a weed of cropping in Australia. Animals do not eat the plant.	P & C (2001)	L
21. Affect land value?	Infested areas are not large. Not likely to seriously affect land value.	P & C (2001)	L
22. Change land use?	Infested areas are not large. Not likely to dictate a change in land use in pasture situations.	P & C (2001)	L
23. Increase harvest costs?	Not a weed of cropping in Australia.	P & C (2001)	L
24. Disease host/vector?	“A closely related species is an important host for a virus disease of tobacco in parts of Africa.” Potential to host a serious disease of important agricultural produce.	P & C (2001)	H

Impact Assessment Record - Ivy-leafed sida (PDF - 30KB)
Impact Assessment Record - Ivy-leafed sida (DOC - 56KB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

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