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Impact Assessment - Florida blackberry (Rubus argutus) in Victoria

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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.

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 Florida blackberry

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: Florida blackberry
Scientific name: Rubus argutus

Question
Comments
Rating
Confidence
Recreation
1. Restrict human access?Prickly shrub to 2.5 m tall (NPDC, 2006) that forms impenetrable thickets (Smith, 1985), see also photo from ISI (2005), a major impediment to human access.
H
MH
2. Reduce tourism?The ability of this tall, prickly shrub (NPDC, 2006) to grow in boggy soil (Tunison, 1991) and form impenetrable thickets (Smith, 1985) may have a major impact on recreation around waterways, restricting access and being obvious to most visitors.
H
MH
3. Injurious to people?Prickles up to 8 mm long on stems (always present) and also prickles on leaf margins most of the year (deciduous) (Tunison, 1991)
MH
MH
4. Damage to cultural sites?Moderate visual effect caused by large, prickly shrub (NPDC, 1991).
ML
MH
Abiotic
5. Impact flow?Able to grow in boggy soil (Tunison, 1991) but not recorded in permanent water. Terrestrial species.
L
MH
6. Impact water quality?Able to grow in boggy soil (Tunison, 1991) but not recorded in permanent water. Terrestrial species.
L
MH
7. Increase soil erosion?Forms thickets (Smith, 1985) and able to grow in boggy soil (Tunison, 1991) which may enable it to bind soil otherwise prone to soil erosion.
L
MH
8. Reduce biomass?“Habitat-disruptive when dense clonal thickets form…Most other native plants are excluded from these thickets when fully developed” (Tunison, 1991). Where this plant replaces taller species it will reduce biomass slightly.
MH
MH
9. Change fire regime?“Habitat-disruptive when dense clonal thickets form…Most other native plants are excluded from these thickets when fully developed” (Tunison, 1991). Although this plant does burn (Smith, 1985) it does not provide a dried fuel source like the grasses that it replaces so it would cause a minor decrease in fire intensity.
ML
MH
Community Habitat
10. Impact on composition
(a) high value EVC
EVC= Montane riparian woodland (V); CMA=North East; Bioreg=Highlands-Northern Fall; CLIMATE potential=M.
Displaces all species within the ground and/or shrub layers.
H
MH
(b) medium value EVCEVC= Montane grassy woodland (D); CMA=North East; Bioreg=Highlands-Northern Fall; CLIMATE potential=M.
“Smother[s] vegetation, displacing the native species or preventing their re-establishment” (Smith, 1985). Grows to 2.5 m tall (NPDC, 2006). Displaces all species within the ground and/or shrub layers.
H
MH
(c) low value EVCEVC= Riparian forest (LC); CMA=North East; Bioreg=Highlands-Northern Fall; CLIMATE potential=M.
“Smother[s] vegetation, displacing the native species or preventing their re-establishment” (Smith, 1985). Grows to 2.5 m tall (NPDC, 2006). Displaces all species within the ground and/or shrub layers.
H
MH
11. Impact on structure?“Habitat-disruptive when dense clonal thickets form…Most other native plants are excluded from these thickets when fully developed, although some [vigorous, shade-tolerant species] tolerate or even penetrate a blackberry canopy…Forms large thickets in upper elevation forests” (Tunison, 1991). “Smother[s] vegetation, displacing the native species or preventing their re-establishment” (Smith, 1985). Grows to 2.5 m tall (NPDC, 2006). Able to have a major effect on the ground and shrub layers, displacing most or all of the species, but unlikely to out compete the trees.
MH
MH
12. Effect on threatened flora?12. Effect on threatened flora?No information found.
MH
L
Fauna
13. Effect on threatened fauna?No information found.
MH
L
14. Effect on non-threatened fauna?One of 12 of the most significant environmental weeds on the Hawaiian Islands…serious threat to native ecosystems (Smith, 1985). “Smother[s] vegetation, displacing the native species or preventing their re-establishmentö (Smith, 1985). Large infestations could reduce habitat and food sources for native fauna, leading to a local reduction in numbers.
MH
MH
15. Benefits fauna?Palatable to grazing animals (Caldwell et. al, 2001). May provide an alternative food source for grazing animals and some bird species that might eat the berries (Parsons & Cuthbertson, 1992) and shelter for small vertebrates due to its thorny nature (Tunison, 1991).
MH
MH
16. Injurious to fauna?Prickles up to 8 mm long on stems (always present) and also prickles on leaf margins most of the year (deciduous) (Tunison, 1991). Sheep can become entangled in the canes of the related and similar R. fruticosus (Parsons & Cuthbertson, 1992). Dangerous to fauna.
H
MH
Pest Animal
17. Food source to pests?Birds and foxes eat the fruit of the related R. fruticosus (Parsons & Cuthbertson, 1992). Provides
MH
MH
18. Provides harbor?The related, and similar R. fruticosus harbours foxes and rabbits (Parsons & Cuthbertson, 1992), although Florida blackberry is deciduous (Tunison, 1991) so wouldn’t provide harbour for the whole year.
MH
MH
Agriculture
19. Impact yield?Grows in plantations (Tunison, 1991), but no evidence found of this plant as an agricultural weed (in Smith, 1985 or Tunison, 1991), probably because they are palatable to grazing animals (Caldwell et. al, 2001). Unlikely to impact yield.
L
H
20. Impact quality?See Q 19. Not a weed of agriculture.
L
H
21. Affect land value?See Q 19. Not a weed of agriculture.
L
H
22. Change land use?See Q 19. Not a weed of agriculture.
L
H
23. Increase harvest costs?See Q 19. Not a weed of agriculture.
L
H
24. Disease host/vector?Not noted as a disease host/vector (in Smith, 1985 or Tunison, 1991).
L
MH

This table can also be viewed as a PDF document (printer friendly).

Impact Assessment Record - Florida blackberry (PDF - 255KB)
Impact Assessment Record - Florida blackberry (DOC - 340KB)
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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