Impact Assessment - Peppercorn tree (Schinus molle) 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 Peppercorn tree.
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: Peppercorn tree
Scientific name: Schinus molle
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | It is described as freely coppicing and as forming extensive species poor stands (Weber 2003), and although not specifically documented, it has some potential to restrict human access. | M | M |
| 2. Reduce tourism? | No information was found to suggest it reduces tourism, but as a large tree to 10 m tall (Blood 2001) it is likely to be obvious to the ‘average’ visitor and may affect the aesthetics of an area. | ML | MH |
| 3. Injurious to people? | Fruit are allergenic, especially toxic to children, causing vomiting, gastro-enteritis, irritation of mucous membranes, allergic dermatitis, hay fever, asthma and breathing difficulties (Shepherd 2004). Major component in allergies, hay fever and asthma. | MH | MH |
| 4. Damage to cultural sites? | Older trees grow top heavy, can blow down in storms and are consequently no longer planted on public streets in Riverside, California for fear of law suits (Howard & Minnich 1989). Has potential to cause damage to property, though this appears not directly as a result of its growth habit. Its gum is also documented as causing damage to car duco (Landcare 2007). | M | M |
| Abiotic | |||
| 5. Impact flow? | Terrestrial species, not likely to impact water flow. | L | M |
| 6. Impact water quality? | Terrestrial species, not likely to impact water quality. | L | M |
| 7. Increase soil erosion? | ‘Since the soil under the canopy can remain bare and lacks an herbaceous ground flora, erosion can be accelerated in stands growing on slopes or near streams (Weber 2003)’. Moderate probability of large scale soil movement. | ML | MH |
| 8. Reduce biomass? | Grows as a ‘tree in a shrubland’ (Howard & Minnich 1989). Could increase the biomass of a community. | L | MH |
| 9. Change fire regime? | It is described growing as a ‘tree in a shrubland’ capable of shading out all native vegetation (Weber 2003) and there is suggestion that it could turn scrublands into savannahs (Howard & Minnich 1989). It is also described as fire retardant (Zanthorrea 2007) so there is potential for it to decrease fire intensity in some communities and also have a moderate affect on fire frequency. | MH | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Riparian scrub (BCS= E); CMA= Wimmera; Bioreg= Wimmera; CLIMATE potential=VH. ‘It is freely coppicing and forms extensive species poor stands that shade out all native vegetation (Weber 2003)’. Grows as a ‘tree in a shrubland’ (Howard & Minnich 1989). Major displacement of dominant species. | MH | MH |
| (b) medium value EVC | EVC= Low Chenopod shrubland (BCS= D); CMA= Mallee; Bioreg= Murray Scroll Belt; CLIMATE potential=VH. ‘It is freely coppicing and forms extensive species poor stands that shade out all native vegetation (Weber 2003)’. Grows as a ‘tree in a shrubland’ (Howard & Minnich 1989). Major displacement of dominant species. | MH | MH |
| (c) low value EVC | EVC= Shrubby Riverine Woodland (BCS= LC); CMA= Mallee; Bioreg= Murray Mallee; CLIMATE potential=VH. ‘It is freely coppicing and forms extensive species poor stands that shade out all native vegetation (Weber 2003)’. Grows as a ‘tree in a shrubland’ (Howard & Minnich 1989). Major displacement of dominant species. | MH | MH |
| 11. Impact on structure? | ‘S. molle potentially alters structure and composition in grasslands, woodlands and coastal scrub areas (Morisawa 2000)’. Forms extensive species poor stands that shade out all native vegetation (Weber 2003). Not described as forming monocultures. | MH | MH |
| 12. Effect on threatened flora? | Forms extensive species poor stands that shade out all native vegetation (Weber 2003). ‘S. molle potentially alters structure and composition in grasslands, woodlands and coastal scrub areas (Morisawa 2000)’. Likely to impact on threatened flora species but not specifically documented. | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | Forms extensive species poor stands that shade out all native vegetation (Weber 2003). Likely to alter habitat by eliminating native vegetation but its specific impact on fauna was not found documented. | MH | L |
| 14. Effect on non-threatened fauna? | Forms extensive species poor stands that shade out all native vegetation (Weber 2003)’. Likely to alter habitat by eliminating native vegetation but its specific impact on fauna was not found documented. | M | L |
| 15. Benefits fauna? | In degraded locations mature trees may provide food and shelter to native animals including birds, bats and possums (Muyt 2001). Leaves consumed by the native Emperor Gum moth (French 1945). Berries fed on by the threatened Spotted Bower bird (Walker & Christian 2003). Provides some assistance in food and shelter to desirable species. | MH | MH |
| 16. Injurious to fauna? | Fruit and leaves cause poisoning or death in poultry, pigs and possibly calves (Blood 2001). It could be toxic to some fauna but no information was found documented. | M | M |
| Pest Animal | |||
| 17. Food source to pests? | ‘Seed is possibly dispersed by foxes (Muyt 2001)’. Fruits are eaten in large quantities by the ‘Patagonian Fox’ in South America (Silva et al 2005). Because it fruits year round it has the potential to provide food throughout the year to one serious pest. | MH | M |
| 18. Provides harbour? | Not described as providing harbour for any serious pest animals, e.g. foxes or rabbits, and as a tree (Howard & Minnich 1989) is unlikely to, but most likely to provide harbour for minor pest species such as exotic birds. | ML | MH |
| Agriculture | |||
| 19. Impact yield? | A pest in orange groves and other sites of irrigation (Howard & Minnich 1989) but not documented as impacting on yield. | L | M |
| 20. Impact quality? | There is no information to suggest it impacts on agricultural quality. | L | M |
| 21. Affect land value? | There is no information to suggest it impacts on agricultural quality. | L | M |
| 22. Change land use? | There is no information to suggest it would cause a change in land use. | L | M |
| 23. Increase harvest costs? | Described as a pest in orange groves and sites of irrigation (Howard & Minnich 1989) but it is not clear from the information available whether it may increase harvest costs, for example due to increased irrigation requirements. | M | L |
| 24. Disease host/vector? | ‘Host of fruit fly (Blood 2001)’. Host of a major agricultural pest. | H | MH |
Impact Assessment Record - Peppercorn tree (PDF - 67KB)
Impact Assessment Record - Peppercorn tree (DOC - 58KB)
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