Pelican Lagoon Islet Pilot Vegetation Survey
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Pelican Lagoon Pilot Vegetation Survey 2017 1 PROGRAM This project is supported by Natural Resources Kangaroo Island, through funding from the Australian Government’s National Landcare Programme. The views expressed and the conclusions reached in this report are those of the author and not necessarily those of persons consulted. Natural Resources Kangaroo Island shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report.
NATURAL RESOURCES KANGAROO ISLAND CONTACT DETAILS 37 Dauncey Street Kingscote SA 5223 Phone: (08) 8553 4444 Email: [email protected]
AUTHORS Kym Lashmar Veronica Bates Heiri Klein
YEAR OF PUBLICATION 2017
© Natural Resources Kangaroo Island
This document may be reproduced in whole or part for the purpose of study or training, subject to the inclusion of an acknowledgment of the source and to its not being used for commercial purposes or sale. Reproduction for purposes other than those given above requires prior written permission from Natural Resources Kangaroo Island.
For bibliographic purposes this paper should be cited as: Lashmar, K, Bates, V & Klein, H 2017. Pelican Lagoon Islet Pilot Vegetation Survey. Natural Resources Kangaroo Island, Catchment to Coast Project Report.
FRONT COVER IMAGES: Malva preissiana (Australian Hollyhock) on Goanna Islet (left). View of Pig Islet taken from Wallaby Islet (right).
Pelican Lagoon Pilot Vegetation Survey 2017 2 CONTENTS
CONTENTS ...... 3
TABLES, FIGURES AND PLATES ...... 4
INTRODUCTION ...... 6
STUDY AREA ...... 8
SURVEY METHOD ...... 11
RESULTS ...... 12
COMBINED PLANT SPECIES SUMMARY ...... 12
INDIVIDUAL ISLET SUMMARIES...... 14
WALLABY ISLET ...... 14 General Description ...... 15 Rare or Threatened Plants ...... 16 Weeds ...... 16 GOANNA ISLET ...... 17 General Description ...... 18 Rare or Threatened Plants ...... 19 Weeds ...... 19 RABBIT ISLET ...... 20 General Description ...... 21 Rare or Threatened Plants ...... 22 Weeds ...... 23 PIG ISLET ...... 24 General Description ...... 25 Rare or Threatened Plants ...... 26 Weeds ...... 26 SHAG ROCK ...... 27 General Description ...... 28 Rare or Threatened Plants ...... 29 Weeds ...... 29
DISCUSSION ...... 30
RECOMMENDATIONS ...... 32
REFERENCES ...... 33
APPENDICES...... 35
Appendix 1: Plant species list including islet distribution ...... 35
Pelican Lagoon Pilot Vegetation Survey 2017 3 TABLES, FIGURES AND PLATES
TABLES
TABLE 1: PELICAN LAGOON ISLET VEGETATION SURVEY LOCATIONS...... 8
TABLE 2: SUMMARY OF PLANT SPECIES RECORDED ON EACH ISLET...... 13
TABLE 3: WALLABY ISLET RARE OR THREATENED PLANT SPECIES...... 16
TABLE 4: WALLABY ISLET INTRODUCED PLANT SPECIES...... 16
TABLE 5: GOANNA ISLET RARE OR THREATENED PLANT SPECIES...... 19
TABLE 6: GOANNA ISLET RARE INTRODUCED PLANT SPECIES...... 19
TABLE 7: RABBIT ISLET RARE OR THREATENED PLANT SPECIES...... 22
TABLE 8: RABBIT ISLET INTRODUCED PLANT SPECIES...... 23
TABLE 9: PIG ISLET RARE OR THREATENED PLANT SPECIES...... 26
TABLE 10: PIG ISLET INTRODUCED PLANT SPECIES...... 26
TABLE 11: SHAG ROCK RARE OR THREATENED PLANT SPECIES...... 29
TABLE 12: SHAG ROCK INTRODUCED PLANT SPECIES...... 29
FIGURES
FIGURE 1: PELICAN LAGOON LOCATION MAP...... 7
FIGURE 2: PELICAN LAGOON BROAD VEGETATION COMMUNITIES...... 9
FIGURE 3: SUMMARY OF PLANT SPECIES RECORDED ON EACH ISLET ...... 13
PLATES
PLATE 1: RV HARLEQUIN MOORED ON THE SHORE OF PIG ISLET, PELICAN LAGOON...... 11
PLATE 2: THE SA RARE SPECIES XANTHOSIA TASMANICA (SOUTHERN XANTHOSIA) RECORDED ON RABBIT ISLET...... 12
PLATE 3: THE INTRODUCED WONS SPECIES ASPARAGUS ASPARAGOIDES (BRIDAL CREEPER) RECORDED ON EVERY ISLET...... 12
PLATE 4: WATER LEVEL VIEW OF WALLABY ISLET...... 14
PLATE 5: AERIAL VIEW OF WALLABY ISLET...... 14
PLATE 6: MODERATE SHRUBLAND COMMUNITY PRESENT IN THE EASTERN-HALF OF WALLABY ISLET...... 15
PLATE 7: COASTAL SALTMARSH COMMUNITY PRESENT AROUND MUCH OF THE SHORELINE OF WALLABY ISLET...... 15
PLATE 8: DEGRADED WESTERN-PORTION OF WALLABY ISLET...... 16
PLATE 9: LARGE REMNANT MELALEUCA LANCEOLATA (DRYLAND TEA-TREE) FOUND ON WALLABY ISLET...... 16
PLATE 10: WATER LEVEL VIEW OF GOANNA ISLET...... 17
PLATE 11: AERIAL VIEW OF GOANNA ISLET...... 17
Pelican Lagoon Pilot Vegetation Survey 2017 4 PLATE 12: THE LANDSCAPE OF GOANNA ISLET IS LARGELY DOMINATED BY LYCIUM FEROCISSIMUM (AFRICAN BOXTHORN)...... 18
PLATE 13: SMALL POCKET OF INTACT NATIVE SHRUBLAND AT THE EAST END OF GOANNA ISLET...... 18
PLATE 14: COASTAL SALTMARSH COMMUNITY PRESENT ALONG THE SOUTHERN SHORELINE OF GOANNA ISLET...... 18
PLATE 15: THE NATIVE SPECIES MALVA PREISSIANA (AUSTRALIAN HOLLYHOCK) PRESENT ON GOANNA ISLET...... 18
PLATE 16: WATER LEVEL VIEW OF RABBIT ISLET...... 20
PLATE 17: AERIAL VIEW OF RABBIT ISLET...... 20
PLATE 18: REMNANT EUCALYPTUS DIVERSIFOLIA SSP. DIVERSIFOLIA (COASTAL WHITE MALLEE) TREES SURROUND RABBIT ISLET...... 21
PLATE 19: THICK TALL SHRUBLAND FOUND IN POCKETS THROUGHOUT RABBIT ISLET...... 21
PLATE 20: CLEARED AREAS ON RABBIT ISLET OFTEN CONTAIN INTRODUCED FOENICULUM VULGARE (FENNEL) PLANTS...... 22
PLATE 21: A MIXTURE OF VEGETATED AND NON-VEGETATED AREAS CREATE A PATCHWORK LANDSCAPE ON RABBIT ISLET...... 22
PLATE 22: PANDION HALIAETUS (OSPREY) NEST IN A MELALEUCA HALMATURORUM (SWAMP PAPER-BARK) TREE ON THE NORTHERN
SHORELINE OF THE ISLET ...... 22
PLATE 23: WATER LEVEL VIEW OF PIG ISLET...... 24
PLATE 24: AERIAL VIEW OF PIG ISLET...... 24
PLATE 25: LIMESTONE ROCKS PILED INTO ARTIFICIAL MOUNDS...... 25
PLATE 26: LANDSCAPE OF PIG ISLET DOMINATED BY INTRODUCED SPECIES INC. LYCIUM FEROCISSIMUM (AFRICAN BOXTHORN)...... 25
PLATE 27: COASTAL SALTMARSH COMMUNITY PRESENT ALONG MUCH OF THE SHORELINE OF PIG ISLET...... 25
PLATE 28: EVIDENCE THAT A SIGNIFICANT POPULATION OF MICE INHABIT PIG ISLET...... 25
PLATE 29: WATER LEVEL VIEW OF SHAG ROCK...... 27
PLATE 30: AERIAL VIEW OF SHAG ROCK...... 27
PLATE 31: THE LANDSCAPE OF SHAG ROCK IS DOMINATED BY LYCIUM FEROCISSIMUM (AFRICAN BOXTHORN)...... 28
PLATE 32: VIEW FROM SHAG ROCK WITH WALLABY ISLET & PROSPECT HILL IN THE BACKGROUND...... 28
PLATE 33: VIEW FROM SHAG ROCK WITH MUSTON IN THE BACKGROUND...... 28
PLATE 34: VIEW FROM SHAG ROCK WITH PROSPECT HILL IN THE BACKGROUND...... 28
Pelican Lagoon Pilot Vegetation Survey 2017 5 INTRODUCTION
Pelican Lagoon is a semi-enclosed, shallow marine lagoon located at the western end of Eastern Cove, Nepean Bay, on the north-eastern coastline of Kangaroo Island (Figure 1). The waterbody of Pelican Lagoon comprises two large interconnected basins that range in depth from <1m to >9m (Ballantine- Swan 2009). Located at the northern tip of Pelican Lagoon is the urban centre of American River (population 227), Kangaroo Island’s third largest township (Ballantine-Swan 2009). The surrounding landscape consists mainly of rural agricultural land that was first settled in 1836 (Ballantine-Swan 2009). Land division first occurred in the 1870s, with pastoralists clearing land to graze sheep (Ballantine-Swan 2009).
Pelican Lagoon is one of South Australia’s oldest marine protected areas, being gazetted as the American River Aquatic Reserve in 1971, primarily to conserve habitat and nursery grounds for commercially important fish species such as King George whiting (Sallaginodes punctata) (Baker 2004; PIRSA Fisheries and Aquaculture 2011). The reserve was re-proclaimed in November 2007 to bring it in line with the Fisheries Management Act 2007 (PIRSA Fisheries and Aquaculture 2011). Pelican Lagoon’s conservation value was further acknowledged in 2012 when it was gazetted a Sanctuary Zone within the Encounter Marine Park (Figure 1).
Recently, Eco-Action Kangaroo Island, with the support of Friends of Dudley Peninsula Parks, have proposed a restoration project for the islets of Pelican Lagoon aimed at controlling weeds, increasing biodiversity and enhancing ecosystem resilience. The Pelican Lagoon catchment is also one of the focus areas of Natural Resources Kangaroo Island’s On-ground Works Program, which assists local landholders with the delivery of revegetation and weed management projects. Weed control efforts on private properties around Pelican Lagoon have been challenging, in part due to the presence of source populations of a number of weed species, including African Boxthorn, on the nearby islets. Any effective ecological restoration program within the Pelican Lagoon catchment must therefore include the Pelican Lagoon islets if lasting outcomes across the catchment are to be achieved. Knowledge gained from this vegetation survey, and from the proposed restoration works and associated weed control activities on the islets, will therefore be of direct benefit to natural resource management across the entire catchment.
Pelican Lagoon Pilot Vegetation Survey 2017 6
Figure 1: Pelican Lagoon Location Map.
Pelican Lagoon Pilot Vegetation Survey 2017 7 STUDY AREA
Within Pelican lagoon are five rocky islets, which are the focus of the vegetation survey outlined in this report. These islets are; Wallaby Islet (Section 475), Goanna Islet (Section 476), Rabbit Islet (Section 477), Pig Islet (Section 478) and Shag Rock (Section 479) (Figure 1; Table 1). These islets, along with the peninsula to the north of the lagoon, form the Pelican Lagoon Conservation Park (Figure 1). The lagoon’s islets, and a thin coastal strip to the north of the lagoon, were initially dedicated as Conservation Park in 1967, however a large area adjacent to the coastal strip, and a portion of Crown Land (Section 462), were later added in 1984, increasing the parks overall size to 397 ha (NPWS 1987) (Figure 1).
Table 1: Pelican Lagoon Islet Vegetation Survey locations.
Name Section # Area (ha) Easting Northing
Wallaby Islet 475 18.33 750520 6032368
Goanna Islet 476 6.99 751579 6031971
Rabbit Islet 477 13.35 753320 6032410
Pig Islet 478 3.89 750945 6032816
Shag Rock 479 0.50 750324 6032942
Prior to the 1930s several areas surrounding the lagoon were used to grow barley, and up until the 1950s much of the mainland sections were burnt for grazing (NPWS 1987). Melaleuca halmaturorum from the surrounding areas was harvested until at least the 1950s to be used as fence posts (NPWS 1987; K. Lashmar personal observation c.2008). The last known fire in the area occurred during the 1950s, and was lit to clear regenerating vegetation (NPWS 1987). It has been reported that sometime after the area was settled, the islets were cleared and used to graze stock (NPWS 1987; Overton et al. 1988), however little is known about the pre-European flora on the islets. NPWS (1987) does however report that, with the exception of the edges of the islets, the vegetation on the islets consists of low shrubland or low open shrubland/grassland. NPWS (1987) also states that they all contain introduced African boxthorn (Lycium ferocissimum) and other introduced herb species as well as the native plant associations. NPWS (1987) reports that Section 479 (Shag Rock) is particularly dominated by ‘boxthorn and nettles’.
Pelican Lagoon Pilot Vegetation Survey 2017 8 The remnant vegetation surrounding the lagoon is a mixture of Leucopogon parviflorus shrubland, Myoporum insulare tall open shrubland, Melaleuca halmaturorum tall open shrubland/low woodland, Tecticornia, Suaeda & Sarcocornia spp. samphire saltmarsh, and a mixture of open mallee communities dominated by Eucalyptus rugosa, E. diversifolia and E. cneorifolia (Figure 2). The vegetation on the islets themselves has been mapped (outlined), but not assigned a vegetation community, therefore the community is not formally known (Figure 2).
Figure 2: Pelican Lagoon broad vegetation communities.
Between 1985 and 1986, Overton et al. (1988) made approx. 15 individual trips to the islets of Pelican Lagoon to formally document the flora associations present. A total of 53 native, and 36 introduced species were recorded as part of that survey. Overton et al. (1988) also stated that the numbers of species on each islet appeared to be related to islet size.
Given that 30 years have passed since the original Overton et al. (1988) survey, it is likely that the vegetation on the islets has changed significantly during that time. Planning any restoration works using 30 year old data would be unwise, therefore an up-to-date understanding of the vegetation on the Pelican Lagoon islets is required.
Pelican Lagoon Pilot Vegetation Survey 2017 9 The aims of the current study are to:
1. Re-survey the vegetation that inhabits the islets of Pelican Lagoon, 2. Document the distribution of species between the different islets, 3. Identify rare, threatened and invasive species that are present on the islets, and 4. Compare final results with those recorded by Overton et al (1988) to identify changes in vegetation types, species or distribution.
The results from this study can then be used to better inform management decisions regarding any possible restoration works that are to be undertaken on the islets.
Pelican Lagoon Pilot Vegetation Survey 2017 10 SURVEY METHOD
The survey method used in this study was a basic Ramble Survey technique. A Ramble Survey consists of wandering (rambling), throughout the vegetation, noting all vegetation types and identifying and recording all native and exotic plant species encountered. Species are recorded to binomial species level; trinomial species level may be applied where possible. During the ‘ramble’ a slow and steady pace is generally maintained, pausing from time to time to record smaller or more cryptic species. Particular attention is payed to searching for threatened, rare or cryptic species that are known to occur in the general area.
Where species cannot be identified, a voucher is taken and assigned a unique identification number. These vouchers are later identified in-office with the use of additional reference material. In instances where a voucher cannot be identified to species level, it may be identified to genus or family level (this mainly applies to young seedlings and grasses). References by Berkinshaw (2009), Dashorst & Jessop (2006), Gillam & Urban (2014), Holliday et al. (1994), Jackson (1988), Jessop et al. (2006), Nicolle (2013), Nicolle (1997), Overton & Overton (2012), Overton (2009) and Prescott (1995) were used to aid species identification.
The Pelican Lagoon Islet Pilot Vegetation Survey was conducted on 20 May 2016, and covered all five of the lagoons islets detailed in Table 1. RV Harlequin, a 5.2m Zodiac Pro 12 ridged inflatable vessel was used as transport to-and-from the islets (Plate 1).
Plate 1: RV Harlequin moored on the shore of Pig Islet, Pelican Lagoon.
Pelican Lagoon Pilot Vegetation Survey 2017 11 RESULTS
Combined Plant Species Summary
A total of 73 plant species were recorded during the Pelican Lagoon Islet Pilot Vegetation Survey, comprising 47 native, and 26 introduced species. One native species recorded is classified as Rare under the National Parks And Wildlife Act 1972; Xanthosia tasmanica (Southern Xanthosia) (Plate 2), and four additional native species are listed as regionally Rare by Gillam & Urban (2014); Galium migrans ssp. migrans (Loose Bedstraw), Millotia myosotidifolia (Broad-leaf Millotia), Nitraria billardierei (Nitre-bush) and Tecticornia arbuscular (Shrubby Samphire). Two of the introduced species recorded are Weeds of National Significance (WoNS); Asparagus asparagoides (Bridal creeper) (Plate 3) and Lycium ferocissimum (African Boxthorn). One species was unable to be identified. A full species list, including islet distribution, is provided in Appendix 1.
Plate 2: The SA Rare species Xanthosia tasmanica (Southern Plate 3: The introduced WoNS species Asparagus Xanthosia) recorded on Rabbit Islet. asparagoides (Bridal creeper) recorded on every islet.
Pelican Lagoon Pilot Vegetation Survey 2017 12 The greatest total number of plant species was recorded on Rabbit Islet (50), with Shag Rock recording the lowest number (22) (Table 2; Figure 3). The greatest richness of native plant species was also recorded on Rabbit Islet (37), followed by Wallaby Islet (28). These two islets are the two largest islets in the lagoon. The lowest richness of native species was recorded on Shag Rock (11) which is also the smallest islet in the lagoon (Table 2; Figure 3). The largest number of introduced species was recorded on Goanna Islet (14), with the lowest number recorded on Wallaby Islet (7) (Table 2; Figure 3). Significant overstorey species i.e. trees, were only recorded on Rabbit Islet, and consisted of a single species; Eucalyptus diversifolia ssp. diversifolia (Coastal White Mallee), the majority of which are confined to the periphery of the islet. Several large Melaleuca lanceolata (Dryland Tea-tree) were recorded on Wallaby Islet, however this species is not considered a true significant overstorey species.
Table 2: Summary of plant species recorded on each islet.
Name Total species Indigenous species Introduced species
Wallaby Islet 35 28 7
Goanna Islet 38 24 14
Rabbit Islet 50 37 13
Pig Islet 32 22 10
Shag Rock 22 11 11
Figure 3: Summary of plant species recorded on each islet
Pelican Lagoon Pilot Vegetation Survey 2017 13 INDIVIDUAL ISLET SUMMARIES
Wallaby Islet
Islet area: 18.33ha
Indigenous species: 28
Introduced species: 7
Total plant species: 35
Plate 4: Water level view of Wallaby Islet.
Plate 5: Aerial view of Wallaby Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 14 General Description
The geology of Wallaby Islet is generally rocky with a thin layer of sandy topsoil. Exposed limestone rubble and small boulders are present throughout. The vegetation on Wallaby Islet can be classed as highly modified, as it is partially degraded, and lacks a true overstorey stratum. It does contain a moderate condition mid-storey community that consists of medium to large sized shrub species such as; Leucopogon parviflorus (Coast Beard-heath), Olearia axillaris (Coast Daisy-bush), Pimelea serpyllifolia ssp. serpyllifolia (Thyme Riceflower) and Alyxia buxifolia (Sea Box). This community largely populates the eastern-half of the islet, and extends along the southern shore (Plate 6). Surrounding much of the islet is a very good coastal saltmarsh community (Plate 7) dominated by Tecticornia arbuscula (Shrubby Samphire) and Suaeda australis (Austral Seablite). The western-half of the islet is far more degraded (Plate 8), and consists largely of introduced Lycium ferocissimum (African Boxthorn) shrubs and also several Olea europaea (European Olive) trees, which are not present on any of the other islets. Wallaby Islet did however recorded the fewest introduced species of any of the islets (7). Numerous scats and runways indicate that there is a population of Kangaroos and Wallaby’s present on the islet, with some major runways indicating that there is some movement between the islet and the surrounding shore of Pelican Lagoon to the south.
Plate 6: Moderate shrubland community present in the Plate 7: Coastal saltmarsh community present around much eastern-half of Wallaby Islet. of the shoreline of Wallaby Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 15
Plate 8: Degraded western-portion of Wallaby Islet. Plate 9: Large remnant Melaleuca lanceolata (Dryland Tea- tree) found on Wallaby Islet.
Rare or Threatened Plants
Two KI Rare plant species were recorded on Wallaby Islet (Table 3). Galium migrans ssp. migrans (Loose Bedstraw) is found throughout the islet, while Tecticornia arbuscular (Shrubby Samphire) is restricted to the coastal saltmarsh areas that fringe the islet.
Table 3: Wallaby Islet Rare or Threatened plant species.
Scientific Name Common Name AUS SA KI Notes Galium migrans ssp. migrans Loose Bedstraw R Tecticornia arbuscula Shrubby Samphire R
Weeds
Seven introduced plant species were recorded on Wallaby Islet (Table 4). The species of most concern are the two WoNS species; Lycium ferocissimum (African Boxthorn) and Asparagus asparagoides (Bridal creeper), however Olea europaea (European Olive) and Asphodelus fistulosus (Onion Weed) can also be extremely invasive if left unchecked.
Table 4: Wallaby Islet Introduced plant species.
Scientific Name Common Name WoNS Notes Asparagus asparagoides* Bridal creeper* Y Asphodelus fistulosus* Onion Weed* Diplotaxis tenuifolia* Lincoln Weed* Lycium ferocissimum* African Boxthorn* Y Medicago polymorpha* Burr Medic* Melilotus indicus* King Island Melilot* Olea europaea* European Olive*
Pelican Lagoon Pilot Vegetation Survey 2017 16 Goanna Islet
Islet area: 6.99ha
Indigenous species: 24
Introduced species: 14
Total plant species: 38
Plate 10: Water level view of Goanna Islet.
Plate 11: Aerial view of Goanna Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 17 General Description
The geology of Goanna Islet is far sandier than that of the other islets, with the only real rocky areas present along the northern and western shorelines. The islet’s vegetation can be classified as highly modified, and is largely degraded with Lycium ferocissimum (African Boxthorn) dominating the landscape (Plate 12). Towards the eastern end of the islet is a very small pocket of moderate condition native shrubland dominated by Olearia axillaris (Coast Daisy-bush) and Pimelea serpyllifolia ssp. serpyllifolia (Thyme Riceflower) with the occasional Myoporum insulare (Common Boobialla) (Plate 13). Surrounding the southern shoreline of the islet is a good to very good coastal saltmarsh community (Plate 14) dominated by Tecticornia arbuscula (Shrubby Samphire). Despite the overall poor condition of the islet, it does contain a sizable population of Malva preissiana (Australian Hollyhock) (Plate 15). No presence of native herbivores was observed.
Plate 12: The landscape of Goanna Islet is largely Plate 13: Small pocket of intact native shrubland at the east dominated by Lycium ferocissimum (African Boxthorn). end of Goanna Islet.
Plate 14: Coastal saltmarsh community present along the Plate 15: the native species Malva preissiana (Australian southern shoreline of Goanna Islet. Hollyhock) present on Goanna Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 18 Rare or Threatened Plants
Three KI Rare plant species were recorded on Goanna Islet (Table 5). Galium migrans ssp. migrans (Loose Bedstraw) is present throughout the islet, while Tecticornia arbuscular (Shrubby Samphire) and Nitraria billardierei (Nitre-bush) are restricted to the saline margins of the islet.
Table 5: Goanna Islet Rare or Threatened plant species.
Scientific Name Common Name AUS SA KI Notes Galium migrans ssp. migrans Loose Bedstraw R Reasonably common on KI Nitraria billardierei Nitre-bush R despite its Rare listing. Tecticornia arbuscula Shrubby Samphire R
Weeds
Fourteen introduced species were recorded on Goanna Islet including two WoNS (Table 6). The majority of these species are prevalent throughout the islet.
Table 6: Goanna Islet Rare Introduced plant species.
Scientific Name Common Name WoNS Notes Asparagus asparagoides* Bridal creeper* Y Bromus sp.* Brome grass* Cirsium vulgare* Spear Thistle* Diplotaxis tenuifolia* Lincoln Weed* Erodium cicutarium* Storks Bill* Hypochaeris radicata* Deep-rooted cas's ear* Lagurus ovatus* Hare's Tail Grass* Lolium sp.* Ryegrass* Lycium ferocissimum* African Boxthorn* Y Medicago polymorpha* Burr Medic* Melilotus indicus* King Island Melilot* Solanum nigrum* Black-berry nightshade* Sonchus oleraceus* Common Sow-thistle* Trifolium sp.* Clover*
Pelican Lagoon Pilot Vegetation Survey 2017 19 Rabbit Islet
Islet area: 13.35ha
Indigenous species: 37
Introduced species: 13
Total plant species: 50
Plate 16: Water level view of Rabbit Islet.
Plate 17: Aerial view of Rabbit Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 20 General Description
The geology of Rabbit Islet is generally rocky with a thin layer of sandy topsoil. Exposed limestone rubble and small boulders are present throughout. The vegetation of Rabbit Islet is in better condition than most of the other islets in Pelican Lagoon, but is still regarded as highly modified. Rabbit Islet recorded the greatest richness of native plant species of all the islets. Rabbit Islet is also the only islet to retain a significant overstorey vegetation stratum in the form of remnant Eucalyptus diversifolia ssp. diversifolia (Coastal White Mallee) trees (Plate 18). This overstorey however, is mainly restricted to the periphery of the islet. Parts of the islet are populated by pockets of moderate condition tall closed shrubland (Plate 19) dominated by Leucopogon parviflorus (Coast Beard-heath), Myoporum insulare (Common Boobialla) and Acrotriche patula (Prickly Ground-berry), while other areas are largely cleared and often contain introduced Foeniculum vulgare (Fennel) plants (Plate 20). This creates a patchwork type landscape of vegetated and non-vegetated areas (Plate 21). Along the eastern shoreline of Rabbit Islet is a good to very good coastal saltmarsh community, however this community was not formally assessed at the time of this survey. Numerous scats, runways and sightings indicate that there is a permanent population of Kangaroos and possibly Wallaby’s on the islet, and a hive of feral bees was also observed in a small underground limestone cave. Of conservation significance is a Pandion haliaetus (Osprey) nest located in the canopy of a Melaleuca halmaturorum (Swamp Paper-bark) tree on the far northern shoreline of the islet (Plate 22).
Plate 18: Remnant Eucalyptus diversifolia ssp. diversifolia Plate 19: Thick tall shrubland found in pockets throughout (Coastal White Mallee) trees surround Rabbit Islet. Rabbit Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 21
Plate 20: Cleared areas on Rabbit Islet often contain Plate 21: A mixture of vegetated and non-vegetated areas introduced Foeniculum vulgare (Fennel) plants. create a patchwork landscape on Rabbit Islet.
Plate 22: Pandion haliaetus (Osprey) nest in a Melaleuca halmaturorum (Swamp Paper-bark) tree on the northern shoreline of the islet
Rare or Threatened Plants
One SA Rare, and two KI Rare plant species were recorded on Rabbit Islet (Table 7). Xanthosia tasmanica (Southern Xanthosia) and Millotia myosotidifolia (Broad-leaf Millotia) were found in the understorey of the tall closed shrubland community, likely due to the damp and cool microclimate that the overstorey of this community creates. Galium migrans ssp. migrans (Loose Bedstraw) is present throughout the islet.
Table 7: Rabbit Islet Rare or Threatened plant species.
Scientific Name Common Name AUS SA KI Notes Xanthosia tasmanica Southern Xanthosia R Galium migrans ssp. migrans Loose Bedstraw R Millotia myosotidifolia Broad-leaf Millotia R
Pelican Lagoon Pilot Vegetation Survey 2017 22 Weeds
Thirteen introduced species were recorded on Rabbit Islet including two WoNS (Table 8). The majority of these species can be found throughout the islet, however Lycium ferocissimum (African Boxthorn) is much more prevalent along the western shoreline, and Foeniculum vulgare (Fennel) is largely restricted to cleared areas. Another species of concern is Acacia cyclops (Western Coastal Wattle), which was recorded in very low numbers. This species has the potential to be extremely invasive if left unchecked.
Table 8: Rabbit Islet Introduced plant species.
Scientific Name Common Name WoNS Notes Acacia cyclops* Western Coastal Wattle* Asparagus asparagoides* Bridal creeper* Y Bromus sp.* Brome grass* Diplotaxis tenuifolia* Lincoln Weed* Erodium cicutarium* Storks Bill* Foeniculum vulgare* Fennel* Hypochaeris radicata* Deep-rooted cas's ear* Lagurus ovatus* Hare's Tail Grass* Lycium ferocissimum* African Boxthorn* Y Medicago polymorpha* Burr Medic* Melilotus indicus* King Island Melilot* Sonchus oleraceus* Common Sow-thistle* Trifolium campestre* Hop Clover*
Pelican Lagoon Pilot Vegetation Survey 2017 23 Pig Islet
Islet area: 3.89ha
Indigenous species: 22
Introduced species: 10
Total plant species: 32
Plate 23: Water level view of Pig Islet.
Plate 24: Aerial view of Pig Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 24
General Description
The geology of Pig Islet is generally rocky with a thin layer of sandy topsoil. Exposed limestone rubble and small boulders are present throughout, with rocks piled up into artificial mounds in several places (Plate 25). The vegetation on the islet is classified as non-functional, as there are no terrestrial native vegetation communities present, and the landscape is mainly dominated by introduced plant species including Lycium ferocissimum (African Boxthorn) (Plate 26). As with many of the other islets, the surrounding shoreline of Pig Islet harbours a good coastal saltmarsh community dominated by Tecticornia arbuscula (Shrubby Samphire) and Suaeda australis (Austral Seablite) (Plate 27). No presence of native herbivores was observed, however a significant presence of mice was noted, as the islet was littered with burrows (Plate 28). On the far southern shore of the islet, a possible Little Penguin burrow was observed, however at the time of the survey the burrow was inactive.
Plate 25: Limestone rocks piled into artificial mounds. Plate 26: Landscape of Pig Islet dominated by introduced species inc. Lycium ferocissimum (African Boxthorn).
Plate 27: Coastal saltmarsh community present along much Plate 28: Evidence that a significant population of mice of the shoreline of Pig Islet. inhabit Pig Islet.
Pelican Lagoon Pilot Vegetation Survey 2017 25
Rare or Threatened Plants
One KI Rare plant species was recorded on Pig Islet (Table 9). Tecticornia arbuscular (Shrubby Samphire) is restricted to the saline margins of the islet.
Table 9: Pig Islet Rare or Threatened plant species.
Scientific Name Common Name AUS SA KI Notes Tecticornia arbuscula Shrubby Samphire R
Weeds
Ten introduced species were recorded on Pig Islet including two WoNS (Table 10). The majority of these species are prevalent throughout the islet.
Table 10: Pig Islet Introduced plant species.
Scientific Name Common Name WoNS Notes Asparagus asparagoides* Bridal creeper* Y Bromus sp.* Brome grass* Diplotaxis tenuifolia* Lincoln Weed* Hypochaeris radicata* Deep-rooted cas's ear* Lagurus ovatus* Hare's Tail Grass* Lycium ferocissimum* African Boxthorn* Y Medicago polymorpha* Burr Medic* Petrorhagia dubia* Velvet Pink* Reichardia tingitana* False Sow-thistle* Sonchus oleraceus* Common Sow-thistle*
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Shag Rock
Islet area: 0.50ha
Indigenous species: 11
Introduced species: 11
Total plant species: 22
Plate 29: Water level view of Shag Rock.
Plate 30: Aerial view of Shag Rock.
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General Description
The geology of Shag Rock, as the name suggests, is generally rocky, with exposed limestone rubble and small boulders present throughout. The islet is in extremely poor condition, with the vegetation classified as non-functional. It is almost exclusively dominated by introduced Lycium ferocissimum (African Boxthorn) shrubs (Plates 31 - 34). No terrestrial native vegetation communities are present on the islet. There were as many introduced species recorded on the islet as there were native, which somewhat shows just how degraded this islet has become. Along the northern shore is a small section of moderate to good coastal saltmarsh community dominated by Tecticornia arbuscula (Shrubby Samphire) and Suaeda australis (Austral Seablite). No presence of native herbivores was observed.
Plate 31: The landscape of Shag Rock is dominated by Plate 32: View from Shag Rock with Wallaby Islet & Lycium ferocissimum (African Boxthorn). Prospect Hill in the background.
Plate 33: View from Shag Rock with Muston in the Plate 34: View from Shag Rock with Prospect Hill in the background. background.
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Rare or Threatened Plants
Two KI Rare plant species were recorded on Shag Rock (Table 11). Galium migrans ssp. migrans (Loose Bedstraw) was present in very low numbers, while Tecticornia arbuscular (Shrubby Samphire) is restricted to the northern saline margins of the islet.
Table 11: Shag Rock Rare or Threatened plant species.
Scientific Name Common Name AUS SA KI Notes Galium migrans ssp. migrans Loose Bedstraw R Tecticornia arbuscula Shrubby Samphire R
Weeds
Eleven introduced species were recorded on Shag Rock including two WoNS (Table 12). These species are prevalent throughout the islet.
Table 12: Shag Rock Introduced plant species.
Scientific Name Common Name WoNS Notes Asparagus asparagoides* Bridal creeper* Y Brassica tournefortii* Long-fruited Wild Turnip* Cerastium glomeratum* Mouse-ear Chichweed* Chenopodium murale* Green Fat Hen* Diplotaxis tenuifolia* Lincoln Weed* Erodium cicutarium* Storks Bill* Lagurus ovatus* Hare's Tail Grass* Lycium ferocissimum* African Boxthorn* Y Sonchus oleraceus* Common Sow-thistle* Stellaria media* Chickweed* Urtica urens* Stinging nettle*
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DISCUSSION
This survey has identified a total of 73 plant species comprising 47 native, and 26 introduced species. This is slightly less than the 89 (53 native, 36 introduced) species recorded by Overton et al. (1988), however the current survey was conducted during a single day, as opposed to the ~15 individual trips that Overton et al. (1988) made. The current study was also conducted during May 2016, at a time when many annual species were absent from the landscape, meaning that many species that are present during only part of the year, were likely missed. Other species recorded were only present in dead form, meaning that identification was restricted to genus level only. Of the 73 plant species recorded in the present survey, 49 are in common with the Overton et al. (1988) survey, with a further 6 likely to be in common with the Overton et al (1988) survey, but were not fully identified due to reasons stated above. Therefore, the remaining 18 species recorded in the current survey constitute new records for the islets. These new records include the SA Rare species Xanthosia tasmanica (Southern Xanthosia), and also the regionally Rare species Galium migrans ssp. migrans (Loose Bedstraw) and Millotia myosotidifolia (Broad-leaf Millotia). Six of the new records are introduced species, and include; Acacia cyclops (Western Coastal Wattle) – restricted to Rabbit Islet, Cirsium vulgare (Spear Thistle) – restricted to Goanna Islet, and Reichardia tingitana (False Sow-thistle) – restricted to Pig Islet. Acacia cyclops and Cirsium vulgare were only observed in very low numbers, however Reichardia tingitana was present in large numbers on Pig Islet, even though it was absent from all other islets. This would appear to indicate that initial introductions of new species to the islets happen on a somewhat random basis.
It is difficult to make a direct comparison between the results of this survey, and the results of the Overton et al. (1988) survey, as the current survey was conducted during a single day, as opposed to the multiple trips made by Overton et al. (1988). Several interesting changes in vegetation types on the islets were noted however, and these include:
1. Aceana novae-zelandiae (Biddy-biddy) - recorded by Overton et al. (1988) on Wallaby and Rabbit Islets, but not recorded in the current survey. 2. Acrotriche patula (Prickly Ground-berry) - recorded by Overton et al. (1988) on Wallaby, Rabbit and Pig Islets, but only recorded on Rabbit Islet in the current survey. 3. Asparagus asparagoides* (Bridal Creeper*) - only recorded by Overton et al. (1988) on Goanna Islet, but recorded on every islet in the current survey. 4. Austrostipa stipoides (Coast Spear-grass) - not recorded by Overton et al. (1988), but recorded on Rabbit and Pig Islets in the current survey. 5. Bulbine semibarbata (Small Leak-lily) - recorded by Overton et al. (1988) on Wallaby and Rabbit Islets, but not recorded in the current survey.
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6. Carduus tenuiflorus* (Slender Thistle*) - recorded by Overton et al. (1988) on Wallaby, Goanna and Rabbit Islets, but not recorded in the current survey. 7. Eucalyptus diversifolia ssp. diversifolia (Coastal White Mallee) - recorded by Overton et al. (1988) on Wallaby and Rabbit Islets, but only recorded on Rabbit Islet in the current survey. 8. Olea europaea* (Olive*) - recorded by Overton et al. (1988) on Wallaby, Rabbit and Pig Islet, but only recorded on Wallaby Islet in the current survey. 9. Rhagodia candolleana ssp. candolleana (Sea-berry Saltbush) - only recorded by Overton et al. (1988) on Goanna Islet, but recorded on every islet in the current survey. 10. Rhagodia crassifolia (Fleshy Saltbush) - recorded by Overton et al. (1988) on Wallaby, Rabbit and Pig Islets as well as Shag Rock, but not recorded in the current survey. Possible confusion between the two Rhagodia spp. 11. Solanum nigrum* (Black Nightshade*) - recorded by Overton et al. (1988) on every islet, but only recorded on Goanna Islet in the current survey.
The total absence of large overstorey species on all but one of the islets, is likely due to pervious land clearance and burning practices. It is highly likely that many of the larger islets would have supported a significant overstorey stratum prior to European settlement. Why trees such as Eucalyptus diversifolia ssp. diversifolia (Coastal White Mallee), or perhaps Eucalyptus rugosa (Coastal mallee), which surround Pelican Lagoon, have not regenerated on the islets is unclear. It is likely that much of the available seed bank that was once present in the soil has been exhausted through stock grazing and periodic burning. This is likely true for many other plant species that may have once occupied the islets. The widespread native species that are currently on the islets i.e. the species that make up the shrubland communities, are general colonising type species that have likely regenerated from what little remnant seedbank remains, or have re-colonised the islets via natural means. These include Leucopogon parviflorus (Coast Beard-heath) and Myoporum insulare (Common Boobialla) which are both spread largely by birds, and Olearia axillaris (Coast Daisy-bush) which produces large quantities of wind-blown seed. All of these species are also prevalent around the periphery of Pelican Lagoon which provides a constant supply of seed.
In general, all of the islets in Pelican Lagoon are in various states of degradation, with vegetation classified as highly modified or non-functional, and introduced species a prominent feature. Given that the islets form part of the Pelican Lagoon Conservation Park, there is no reason why attempts should not be made to rehabilitate or at least partially rehabilitate these islets back to a more ecologically functional state.
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RECOMMENDATIONS
As a result of this survey, several recommendations can be made:
1. Follow-up survey work. It is recommended that a follow-up vegetation survey be conducted on the Pelican Lagoon islets targeting species that may have been absent at the time of the initial survey in May. This survey should also cover any areas missed during the initial survey, such as the samphire saltmarsh on Rabbit Islet.
2. Vegetation community mapping. No formal vegetation community mapping has been conducted on any of the islets. Therefore, as part of the follow-up survey, existing vegetation communities should be documented and formally mapped.
3. Vegetation restoration works. Consideration should be given to either restoring or partially restoring the vegetation of the islets. These islets are part of the Pelican Lagoon CP, but at present due to their current condition, are not conserving any vegetation of significant value. Potential restoration works on the islets carry with them many logistical challenges, which would need to be considered in great detail. Significant weed control and revegetation works have been conducted on properties surrounding Pelican Lagoon. Therefore, failure to control weeds on the islets would result in the islets themselves acting as a weed seedbank, capable of re-infesting the surrounding properties.
4. Reference sites. To gain a broader understanding of the types of vegetation that may have once existed on the islets of Pelican Lagoon, the vegetation surrounding the lagoon should be surveyed so that representative reference sites can be established. The information obtained from these sites would then be referred to when planning rehabilitation works.
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REFERENCES Baker, J. L. 2004. Towards a System of Ecologically Representative Marine Protected Areas in South Australian Marine Bioregions - Technical Report, Prepared for the Coast and Marine Conservation Branch, Department for Environment and Heritage, South Australia.
Ballantine-Swan, M-A. 2009. Draft Pelican Lagoon Issues Paper. Prepared for Kangaroo Island Natural Resources Management Board, Kingscote, South Australia.
Berkinshaw, T. 2009. Mangroves to Mallee: The complete guide to the vegetation of temperate South Australia. Greening Australia, Adelaide South Australia.
Dashorst, G.R.M. & Jessop, J.P. 2006. Plants of the Adelaide Plains and Hills. Third edition, The Board of the Botanic Gardens of Adelaide and State Herbarium, North Terrace, Adelaide.
Gillam, S. & Urban, R. 2014. Regional Species Conservation Assessment Project, Phase 1 Report: Regional Species Status Assessments, Kangaroo Island NRM Region. Department of Environment, Water and Natural Resources, South Australia.
Holliday, I. Overton, B. & Overton, D. 1994. Kangaroo Island’s Native Plants. Ivan Holliday, Bev Overton and Dean Overton, Adelaide.
Jackson, I. 1988. The Flora of Kangaroo Island. D.J. Woolman Government Printer, South Australia.
Jessop, J., Dashorst, G. R. M. & James, F. M. 2006. Grasses of South Australia: An illustrated guide to the native and naturalised species. The Board of Botanic Gardens of Adelaide and State Herbarium, Adelaide, South Australia.
National Parks and Wildlife Service 1987. Conservation Parks of Kangaroo Island. Department of Environment and Planning, South Australia.
Nicolle, D. 2013. Native Eucalypts of South Australia. Dean Nicolle, South Australia.
Nicolle, D. 1997. Eucalypts of South Australia. Dean Nicolle, Morphett Vale, South Australia.
Overton, B., Mc-Kelvey, M. & Schwaner, T. 1988. A list of native and alien flowering plants on islets in Pelican Lagoon, Kangaroo Island, South Australia, South Australian Naturalist, 63 (2): 44-50 pp.
Overton, B & Overton, D. 2012. Discover Kangaroo Island’s Native Plants. Environmental Realist, Kingscote, South Australia.
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Overton, B. 2009. Kangaroo Island Plant List. Unpublished.
PIRSA Fisheries and Aquaculture 2011. Management Plan for the Pelican Lagoon Aquatic Reserve. Primary Industries and Regions South Australia, Adelaide, South Australia.
Prescott, A. 1995. It’s Blue With Five Petals: Kangaroo Island Field Guide. Ann Prescott & Associates Pty. Ltd., Adelaide, South Australia.
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APPENDICES
Appendix 1: Plant species list including islet distribution
R = Rare * = Introduced species
KI
Species Common Name SA
EPBC
Pig Islet
Shag Rock
Rabbit Islet
Goanna Islet
Wallaby Islet
Acacia cyclops* Western Coastal Wattle* Acacia longifolia ssp. sophorae Coastal Wattle Acrotriche patula Prickly Ground-berry Alyxia buxifolia Sea Box Asparagus asparagoides* Bridal creeper* Asphodelus fistulosus* Onion Weed* Atriplex cinerea Coast Saltbush Austrostipa sp. Spear-grass Austrostipa stipoides Coast Spear-grass Brassica tournefortii* Long-fruited Wild Turnip* Bromus sp.* Brome grass* Carpobrotus rossii Native Pigface Cerastium glomeratum* Mouse-ear Chichweed* Chenopodium murale* Green Fat Hen* Cirsium vulgare* Spear Thistle* Clematis microphylla Old Man's Beard Dianella brevicaulis Short-stem Flax-lily Dichondra repens Kidney Weed Diplotaxis tenuifolia* Lincoln Weed* Enchylaena tomentosa var. tomentosa Ruby Saltbush Erodium cicutarium* Storks Bill* Eucalyptus diversifolia ssp. diversifolia Coastal White Mallee Foeniculum vulgare* Fennel* Frankenia pauciflora var. gunnii Southern Sea-heath Galium migrans ssp. migrans Loose Bedstraw R Geranium retrorsum Grassland Geranium Graminae sp. Grass sp. Hypochaeris radicata* Deep-rooted cas's ear* Lagurus ovatus* Hare's Tail Grass* Leucopogon parviflorus Coast Beard-heath
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Lolium sp.* Ryegrass* Lycium ferocissimum* African Boxthorn* Maireana oppositifolia Salt Bluebush Malva preissiana Australian Hollyhock Medicago polymorpha* Burr Medic* Melaleuca halmaturorum Swamp Paper-bark Melaleuca lanceolata Dryland Tea-tree Melilotus indicus* King Island Melilot* Millotia myosotidifolia Broad-leaf Millotia R Muehlenbeckia adpressa Climbing Lignum Muehlenbeckia gunnii Coastal Climbing Lignum Myoporum insulare Common Boobialla Nitraria billardierei Nitre-bush R Olea europaea* European Olive* Olearia axillaris Coast Daisy-bush Orchidaceae sp. Orchid sp. Orthrosanthus multiflorus Morning Flag Oxalis perennans Native Sorrel Petrorhagia dubia* Velvet Pink* Pimelea serpyllifolia ssp. serpyllifolia Thyme Riceflower Reichardia tingitana* False Sow-thistle* Rhagodia candolleana ssp. Sea-berry Saltbush candolleana Rumex sp. Dock Rytidosperma sp. Wallaby-grass Sarcocornia quinqueflora Beaded Samphire Senecio odoratus Scented Groundsel Senecio picridioides Purple-leaf Groundsel Senecio sp. Groundsel Senecio pinnatifolius var. maritimus Variable Groundsel Solanum nigrum* Black-berry nightshade* Sonchus oleraceus* Common Sow-thistle* Stellaria media* Chickweed* Suaeda australis Austral Seablite Tecticornia arbuscula Shrubby Samphire R Tetragonia implexicoma Bower Spinach Threlkeldia diffusa Coast Bonefruit Trachymene pilosa Dwarf Trachymene Trifolium campestre* Hop Clover* Trifolium sp.* Clover* Unidentified sp. 1 Unidentified plant Urtica urens* Stinging nettle* Vittadinia australasica var. australasica Sticky New Holland Daisy Xanthosia tasmanica Southern Xanthosia R
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