Impact Assessment - Sea spurge (Euphorbia paralias) 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 Sea spurge.
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: Sea spurge
Scientific name: Euphorbia paralias
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | Can grow to 1 m and form dense stands (Blood 2001; Weber 2003). As the sap is described as “dangerously poisonous” causing skin and eye irritation a dense stand would make access by people difficult (Blood 2001). | MH | MH |
| 2. Reduce tourism? | Unknown; there is no evidence reported of the species impacting on tourism. However it is toxic and can form dense stands on beaches which are popular places for recreational activities. | M | L |
| 3. Injurious to people? | Described as “dangerously poisonous” the plants sap is toxic, capable of causing skin irritation and harm to eyes and requires methylated spirits to be removed (Blood 2001). | H | MH |
| 4. Damage to cultural sites? | Unknown; there is no specific evidence reported of the species damaging sites. However it is reported to alter the formation of sand dunes making them steeper and more likely to be undercut (Blood 2001). This may have some impact on middens. | M | L |
| Abiotic | |||
| 5. Impact flow? | Reported to alter sand dune formation (Blood 2001). This may result in changes to the path of flow but shouldn’t restrict it rate. | L | M |
| 6. Impact water quality? | There is no evidence of this occurring. | L | M |
| 7. Increase soil erosion? | The species is a pioneer species of coastal dunes which are by nature prone to erosion. The species has previously been planted with the intent of dune stabilisation (Blood 2001). The resulting dunes however were found to be steeper and more likely to be undercut by wave action (Blood 2001). Heylinger (2002) reports of plants where the sand has been eroded away leaving their roots exposed for observation. Therefore there is a high probability of large scale erosion, it is unknown however if there are any off-site implications. | M | MH |
| 8. Reduce biomass? | The plant is largely a pioneer species (Heylinger 2002). Which would obviously result in an increase in biomass as something is always more than nothing. The species is also however reported to eliminate native vegetation with dense stands (Weber 2003). Therefore there is some loss of biomass, however as the plant forms dense stands overall there is likely to be an increase in biomass. | L | MH |
| 9. Change fire regime? | Unknown. | M | L |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Coastal Dune Grassland (E); CMA= West Gippsland ; Bioreg= Gippsland Plain; VH CLIMATE potential. Can form dense stands which can eliminate native vegetation and prevent establishment of other natives (Weber 2003). Therefore resulting in the major displacement of species. | MH | MH |
| (b) medium value EVC | EVC= Spray-zone Coastal Shrubland (R); CMA= West Gippsland ; Bioreg= Wilsons Promontory; VH CLIMATE potential. Can form dense stands which can eliminate native vegetation and prevent establishment of other natives (Weber 2003). Therefore resulting in the major displacement of species. | MH | MH |
| (c) low value EVC | EVC= Coastal Tussock Grassland (LC); CMA= West Gippsland ; Bioreg= Gippsland Plain; VH CLIMATE potential. Can form dense stands which can eliminate native vegetation and prevent establishment of other natives (Weber 2003). Therefore resulting in the major displacement of species. | MH | MH |
| 11. Impact on structure? | Can form dense stands which can eliminate native vegetation and prevent establishment of other natives (Weber 2003). As the plant is a pioneer species and where it invades, it predominantly forms part of the only layer, this would have a major effect on effectively all layers (Blood 2001; Heylinger 2002). | H | MH |
| 12. Effect on threatened flora? | Unknown. | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | Unknown. | MH | L |
| 14. Effect on non-threatened fauna? | The species can alter dune formation and vegetation composition (Blood 2001; Weber 2003). This could result in impacts to the available shelter and food supply of fauna. Specific evidence is not reported however. | M | L |
| 15. Benefits fauna? | Not reported to be eaten by anything in Australia, and has toxic sap so would have little potential to provide shelter for species (Blood 2001). Therefore thought to provide little support for desirable species. | H | M |
| 16. Injurious to fauna? | Has toxic sap which can cause irritation (Blood 2001; Sayed et al 1980). | H | H |
| Pest Animal | |||
| 17. Food source to pests? | Not reported to be eaten by anything in Australia. | L | M |
| 18. Provides harbour? | Has toxic sap so would have little potential to provide shelter for species (Blood 2001). | L | M |
| Agriculture | |||
| 19. Impact yield? | Not reported as a weed of agriculture. | L | M |
| 20. Impact quality? | Not reported as a weed of agriculture. | L | M |
| 21. Affect land value? | Not reported as a weed of agriculture. | L | M |
| 22. Change land use? | Not reported as a weed of agriculture. | L | M |
| 23. Increase harvest costs? | Not reported as a weed of agriculture. | L | M |
| 24. Disease host/vector? | Not reported as a weed of agriculture. | L | M |
Impact Assessment Record - Sea spurge (PDF - 82KB)
Impact Assessment Record - Sea spurge (DOC - 58KB)
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