Impact Assessment - African lovegrass (Eragrostis curvula) 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?	Grass 30 to 120 cm high. Low nuisance value to humans; not likely restrict access.	P & C (2001)	ML
2. Reduce tourism?	“Found in disturbed soils on roadsides, railway tracks, river banks and waste places.” Apart from its nuisance value when accessing rivers, it is unlikely to affect tourism.	P & C (2001)	ML
3. Injurious to people?	No recorded toxic effects.		L
4. Damage to cultural sites?	As a grass, this sp. unlikely to affect the structure of historical or cultural features. Presence is noticeable and it is, “capable of dominating the ground-flora on lighter soils.” Moderate visual effect.	Muyt (2001)	ML
Abiotic
5. Impact flow?	Although it grows on riverbanks, there is no indication it affects water flow.	P & C (2001)	L
6. Impact water quality?	Not known to affect water quality		L
7. Increase soil erosion?	A cultivar of E. curvula complex is used in New South Wales to control soil erosion. “Some cultivars are still promoted for…soil stabilisation use.”	P & C (2001) Muyt (2001)	L
8. Reduce biomass?	“…ultimately dominates sparse, overgrazed pastures.” “…dominating ground-flora on lighter soils.” Direct replacement of biomass.	P & C (2001) Muyt (2001)	ML
9. Change fire regime?	Is recorded as a fire hazard in the Eurobodalla Shire in New South Wales.	ESC Factsheet 1	H
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Hills herb-rich woodland (E); CMA=Glenelg Hopkins; Bioreg=Victorian Volcanic Plain; VH CLIMATE potential. “…capable of dominating the ground-flora on lighter soils.” Major displacement of grasses/forbs.	Muyt (2001)	MH
(b) medium value EVC	EVC=Grassy dry forest (D); CMA=Glenelg Hopkins; Bioreg=Goldfields; VH CLIMATE potential “…infestations thin out over time under dense overstorey canopies.” Minor displacement of grasses.	Muyt (2001)	ML
(c) low value EVC	EVC=Heathy woodland (LC); CMA=Glenelg Hopkins; Bioreg=Greater Grampians; VH CLIMATE potential “…infestations thin out over time under dense overstorey canopies.” Major displacement of grasses/forbs.	Muyt (2001)	ML
11. Impact on structure?	It is “…capable of dominating the ground-flora on lighter, low-nutrient soils,” and thus likely to have a major effect on the lower stratum.	Muyt (2001)	ML
12. Effect on threatened flora?
Fauna
13. Effect on threatened fauna?
14. Effect on non-threatened fauna?	Although a weed of disturbed neglected areas it also, “highly invasive in heathlands, woodlands, forests, grasslands and riverine environments.” It is highly persistent, dominant, and largely unpalatable, and therefore may have a minor negative impact on food sources for non-threatened fauna. This may lead to reduced populations	P & C (2001) Muyt (2001)	MH
15. Benefits fauna?	No recorded benefits. “Mature plants are largely unpalatable.”	Muyt (2001)	H
16. Injurious to fauna?	There is no evidence of the plant having toxic properties. It does not produce any spines or burrs.		L
Pest Animal
17. Food source to pests?	No evidence of a food source for pest animals. “Mature plants are largely unpalatable.”	Muyt (2001)	L
18. Provides harbor?	Clumping nature of plant may provide limited harbour for rodents.		ML
Agriculture
19. Impact yield?	“In arable areas, cultivation and cropping or the establishment of perennial pasture …gives good control.” The weed is unlikely to have a significant impact in well-managed paddocks.	P & C (2001)	ML
20. Impact quality?	Is not recorded as a weed of cropping; no evidence of contamination in grass seed crop. Pasture hay is a known vector.	P & C (2001)	ML
21. Affect land value?	In arable areas, its presence controlled with good pasture management practices. “…in non-arable areas, it may be better to utilise the plant as a pasture species.” Little influence on land value.	P & C (2001)	L
22. Change land use?	The weed is not a problem in well managed pastures.	P & C (2001)	L
23. Increase harvest costs?	No evidence of increase in harvest costs		L
24. Disease host/vector?	Not evident.		L