Appendix C4
Appendix C Rapid biosecurity risk assessments
Grader grass(Themeda quadrivalvis) / Species information / Establishment risk
Status / Departure points / Transportability / Climate
Habitat suitability
Arrangement of spikelets &
tubercle-based hairs on some glumes
Bundaberg, Qld, April (Australian Weeds Committee n.d.)
Sources: (Keir and Vogler 2006, Queensland Government 2013, Australian Weeds Committee n.d.). / Native to India and Nepal but now also occurs in Thailand, Indonesia, Papua New Guinea, China, the Middle East and tropical America.
First recorded in Australia in 1935 in North QLD. Thought to have been introduced in contaminated straw packaging. Grader grass is now widespread in QLD and NT where it is a major weed. It has naturalised in WA and NSW. Modelling has shown potential for the weed to become widespread across much of the coastal regions in Australia.
Grader grass has not been recorded on Christmas Island or the Cocos (Keeling) Islands (CKI). / Origin / Est.? / Pathway / Likelihood of introduction to PKNP
Air / Sea
Perth3 / N1 / Y / N / Unlikely
Broome3 / Y / Y / N / Very unlikely
Darwin3 / Y1 / Y / N / Unlikely
Fremantle3 / N1 / N / Y / Very unlikely
Christmas Island / N1 / Y / Y / Very unlikely
Cocos Home Island / N1 / N / Y / Very unlikely
Cocos Horsburgh Island / N1 / N / Y / Very unlikely
Cocos West Island / N1 / N / Y / Very unlikely
Remaining islands of the southern atoll / N1 / N / Y / Very unlikely
Indonesia2 / Y / N / Y / Possible
Sri Lanka2 / N1 / N / Y / Very unlikely
1 Potential for naturalised distribution
2 Suspected Illegal Entry Vessels (SIEVs)
3 Australian mainland / Highly transportable by humans and animals via almost any vector including vehicles, machinery, clothing, tents and other equipment.
Transport considered unlikely via the domestic air pathway from Darwin or Perth.
It is possible that grader grass seeds could be transported via the international sea pathway from Indonesia. / Prefers coastal and sub coastal and seasonally dry subtropical and tropical regions. Rain tolerance between 375–4500 mm but adapts to many moisture regimes. Climate is highly suitable.
Can exploit many habitat types but is mainly found in disturbed areas (roadsides, clearings) with free draining soils. Some habitat on PKNP is considered suitable.
Biology & ecology / Impacts to biodiversity
· Tufted erect annual grass to 1–2.5 m high.
· Long narrow leaves 10 mm wide and ~60 cm long on jointed stems. Junction with the blade a membrane to 2.5mm long.
· Seed head 15–60 cm long, reddish brown.
· Seeds germinable at 2–4 months and germinate in 2 weeks, flowering in summer.
· Seed bank viability ~15 months and seeds will not germinate under dense shade.
· Mature plants: golden brown, loose seed heads in complex clusters of spikelets (4–7 mm), tubercle-based (wart-like) hairs towards the tip of some membranous bracts and has a twisted awn. / · Forms dense monocultures that invade native grasslands and replaces native plants reducing biodiversity.
· Outcompetes by smothering and suppressing germination.
· Changes the structure of established ecosystems and the availability of habitat.
Gamba grass
(Andropogon gayanus) / Species information / Establishment risk
Status / Departure points / Transportability / Climate
Habitat suitability
Matures to a V-shaped seedhead,
Darwin, NT, May
Hairy spikelets (Australian Weeds Committee n.d.)
Sources: (Scott 2009, Crowley 2011, Queensland Government 2011, Petty, Setterfield et al. 2012) / Native to Africa but now also occurs in many parts of the world and established in South America.
First planted in Australia in 1931 in NT and QLD in 1942 where it was cultivated for pasture fodder. Its dispersal was aided by its use as a commercial pasture plant. Gamba grass is classified as a pest species in QLD, NT and WA.
Gamba grass has not been recorded on Christmas Island or the Cocos (Keeling) Islands (CKI).
Gamba grass is a Weed of National Significance and it listed as a Key Threatening Process to biodiversity in Northern Australia under the EPBC Act. / Origin / Est.? / Pathway / Likelihood of introduction to PKNP
Air / Sea
Perth3 / N1 / Y / N / Unlikely
Broome3 / N1 / Y / N / Very unlikely
Darwin3 / Y / Y / N / Unlikely
Fremantle3 / N / N / Y / Very unlikely
Christmas Island / N1 / Y / Y / Very unlikely
Cocos Home Island / N1 / N / Y / Very unlikely
Cocos Horsburgh Island / N1 / N / Y / Very unlikely
Cocos West Island / N1 / N / Y / Very unlikely
Remaining islands of the southern atoll / N1 / N / Y / Very unlikely
Indonesia2 / N / N / Y / Very unlikely
Sri Lanka2 / N / N / Y / Very unlikely
1 Potential for naturalised distribution
2 Suspected Illegal Entry Vessels (SIEVs)
3 Australian mainland / Highly transportable by humans and animals via almost any vector including vehicles, machinery, clothing, tents and other equipment.
Transport considered very unlikely. The only origin point where it has naturalised is in Darwin via the domestic air pathway. / Prefers subtropical and tropical regions, in areas <980 m in altitude with between 400 mm–1500 mm annual rainfall. Climate is highly suitable.
Prefers tropical savannah grassland habitat but does colonise other vegetation. Found in drainage lines and riparian zones. Wetland habitat on PKNP is considered marginally suitable.
Biology & ecology / Impacts to biodiversity
· A perennial grass, leaves 30–60 cm long and up to 3 cm wide, a distinctive white midrib is covered with soft hairs.
· Stems are robust and covered in soft hairs.
· The root system spreads up to 1 m from the tussock, close to the soil surface .
· Reproduces by seed contained in fluffy V-shaped seed heads of up to six groups of branches, each containing 2–18 primary branches.
· Up to 244 000 seeds develops per plant in May–June. Seed sets in July and August then spreads rapidly with plants growing actively in the wet season and flowering in April.
· Seed is wind dispersed, however, 90% fall in close proximity to parent plants.
· Mature plants grow up to 4 m tall in tussocks up to 70 cm in diameter. / · The main impacts on the mainland are related to fire. Gamba grass carries high fuel loads, when burnt; the high intensity fires transform woodlands to grassland.
· High demand for nutrients and water over large areas can alter hydrology in wetlands.
· Outcompetes by smothering and suppressing germination.
· Alters the natural nitrogen (N) cycle by taking up N and reducing its availability to other plants.
· Large plants have small spaces between clumps, which reduces feeding habitat for ground dwelling species.
Common sensitive plant
(Mimosa pudica) / Species information / Establishment risk
Status / Departure points / Transportability / Climate
Habitat suitability
Bipinnate leaves close when touched, heated or cooled and at night (Ahmad, Sehgal et al. 2012)
Pinkish-purple flowers and leaves (Ahmad, Sehgal et al. 2012)
Seed pods (CABI 2013)
Sources: (Magda, Duru et al. 2006, Chauhan and Johnson 2009, Ahmad, Sehgal et al. 2012, Atlas of Living Australia 2013, CABI 2013) / Native to tropical America (southern Mexico to mid South America and the Caribbean), now widely distributed through Africa, south North America, south-east Asia and across the Indian and Pacific Ocean islands.
In Australia, common sensitive plant is a pest species in NSW, NT and QLD.
Common sensitive plant has not been recorded on Christmas Island but has naturalised in the Cocos (Keeling) Islands (CKI). / Origin / Est.? / Pathway / Likelihood of introduction to PKNP
Air / Sea
Perth3 / N / Y / N / Unlikely
Broome3 / N1 / Y / N / Very unlikely
Darwin3 / Y / Y / N / Unlikely
Fremantle3 / N / N / Y / Very unlikely
Christmas Island / N1,4 / Y / Y / Very unlikely
Cocos Home Island / Y / N / Y / Likely
Cocos Horsburgh Island / Y / N / Y / Likely
Cocos West Island / Y / N / Y / Likely
Remaining islands of the southern atoll / Y / N / Y / Likely
Indonesia2 / Y / N / Y / Possible
Sri Lanka2 / Y / N / Y / Possible
1 Potential for naturalised distribution
2 Suspected Illegal Entry Vessels (SIEVs)
3 Australian mainland
4 Mimosa pigera/invisa present on Christmas Island since 1963. Invasive since 1973 (Flora of Australia online) / Highly transportable by humans, animals and water via almost any vector including vehicles, machinery, clothing, tents and other equipment.
Common sensitive plant is naturalised on the southern atoll of Cocos (Keeling) Islands. Introduction via the local sea or natural pathways is likely. It is invasive in Sri Lanka and Indonesia. It is possible that it could be introduced via the international sea pathway. / Prefers humid tropical regions but also grows in temperate. In open land at low elevations to 800m with between 1000mm–5000mm annual rainfall. Climate is highly suitable.
Principal habitat includes natural forests, grasslands, riverbanks and irrigation channels. Also persists in irrigation channels and coastal dunes. Habitat on PKNP is considered highly suitable.
Biology & ecology / Impacts to biodiversity
· A creeping annual or perennial herb.
· Woody and often prostrate, stems sparsely and shortly hairy with longer bristles and prickles 2.5–5 mm long.
· Leaves are bipinnate, 1–2 pairs, linear to oblong, sparsely hairy with bristly margins, droop at night or when touched or cooled.
· Flowers globose (round) head, ovoid and pink.
· Reproduces from seed, up to 700 seeds per plant.
· Seed pods are oblong, bristled, 2–6 mm wide with 1–5 seeds. Seeds dispersed by attaching to animal fur and human clothing and equipment.
· Seeds germinate readily, are salt and moisture stress and shade tolerant.
· Grows in freely drained soils with a wide range of pH and soil textures.
· Fast growing, high reproduction potential, long-lived and pioneers in disturbed areas. / · Forms a monotypic groundcover and outcompetes other plants by smothering, monopolising resources, poisoning, and producing spines, thorns or burrs.
· Has the ability to modify ecosystems, alter habitats and reduce native biodiversity.
· Seeds, leaves and other plant parts contain a toxic breakdown product that interferes with animals (NB: impacts to specific fauna and birds species present on PKNP not studied).
Leucaena
(Leucaena leucocephala) / Species information / Establishment risk
Status / Departure points / Transportability / Climate
Habitat suitability
Foliage, flowers and seed pods
Plant on terrace boundaries (CABI 2013)
Sources: (Hwang, Hsu et al. 2010, Invasive Species Specialist Group 2010, ABRS 2013, CABI 2013) / Native to Mexico and Central America (precise native range is blurred by indigenous cultivation as a minor food plant). Now present on every continent and widely distributed through south-east Asia and across the Indian and Pacific Ocean islands where it is cultivated. It is listed by the IUCN as one of the ‘100 of the World’s Worst Invasive Alien Species’.
In Australia, leucaena was/is cultivated but has become a pest species in QLD, NT, WA and NSW.
Laucaena is naturalised and common on Christmas Island where it forms thickets in disturbed areas, infrequently invades undisturbed forest and has rapidly spread across the island.
On the Cocos (Keeling) Islands (CKI) it has naturalised near the kampong on Home Island. / Origin / Est.? / Pathway / Likelihood of introduction to PKNP
Air / Sea
Perth3 / N / Y / N / Unlikely
Broome3 / N1 / Y / N / Very unlikely
Darwin3 / Y / Y / N / Unlikely
Fremantle3 / N / N / Y / Very unlikely
Christmas Island / Y / Y / Y / Possible
Cocos Home Island / Y / N / Y / Likely
Cocos Horsburgh Island / N1 / N / Y / Very unlikely
Cocos West Island / N1 / N / Y / Very unlikely
Remaining islands of the southern atoll / N1 / N / Y / Very unlikely
Indonesia2 / Y / N / Y / Possible
Sri Lanka2 / Y / N / Y / Possible
1 Potential for naturalised distribution
2 Suspected Illegal Entry Vessels (SIEVs)
3 Australian mainland / Highly transportable by humans, animals (including birds) and water via almost any vector including vehicles, machinery, clothing, tents and other equipment.
Laucaena is naturalised on Christmas Island introduction via the domestic air pathway possible.
Naturalised on Home Island. Introduction via the local sea and natural pathways is likely. If introduced to other islands of CKI likelihood would be similar.
It is invasive in Sri Lanka and Indonesia. It is possible that it could be introduced via the international sea pathway. / Prefers tropical and sub-tropical regions. Tolerates a wide range of annual rainfall between 500mm–3500mm and withstands a long dry season. Climate is highly suitable.
Is a habitat generalist, open coastal or riverine, natural and planted forests, grasslands, disturbed/ruderal areas, and shrublands. Habitat on PKNP is considered highly suitable.
Biology & ecology / Impacts to biodiversity
· Shrub/small tree, 1–7 m tall lives 20-40 yrs.
· Leaves with 3–8 pairs of pinnae, each with 7–16 pairs of leaflets.
· Leaflets oblong, 6–19 mm long, unequal-sided, oblique at base, acute or pointy at tip, margins minutely pubescent.
· Inflorescence globose (round), 1.5–2 cm diam.; peduncle 1–4 cm long. Calyx 2.5 mm long, tubular, slightly toothed.
· Petals narrowly rounded, 4.5 mm long, white or greenish. Stamens 8 mm long, whitish; anthers covered with hairs.
· Legume linear-oblong, flat, 10–18 cm long, minutely pubescent, pendulous, often clustered.
· Seeds 10–25, 7–9 mm long, brown, shiny and abundant. / · Aggressive coloniser of ruderal or disturbed sites modifies successional patterns.