Pearson Island

Pearson Island is an island located in the Australian state of South Australia within the Pearson Isles an island group located in the larger group known as the Investigator Group about 63 kilometres (39 miles) southwest by west of Cape Finniss on the west coast of Eyre Peninsula. The group was discovered and named by Matthew Flinders on 13 February 1802. The island group has enjoyed protected area status since the 1960s and since 2011, it has been part of the Investigator Group Wilderness Protection Area. Pearson Island is notable both for its colony of Pearson Island Rock wallaby and for being a destination for scientific research.

This article is about the island in South Australia. For other uses, see Pearson.

Pearson Island
View of Pearson Island from its south end circa 1914 (State Library of South Australia PRG-280-1-12-263)
Pearson Island
Geography
LocationGreat Australian Bight
Coordinates33°57′39″S 134°15′54″E
Area213 ha (530 acres)[1]
Highest elevation238 m (781 ft)[1]
Administration

Description
View of southern end of Pearson Island
Rock formations and southern end of South Pearson Island
Northern anchorage of Pearson Island
"The Craw" rock formation on the northern side of Pearson Island

Pearson Island is located about 63 kilometres (39 miles) south west by west of Cape Finniss and about 25 kilometres (16 miles) south west of Flinders Island. It is the largest of four islands that form the island group known as the Pearson Isles or the Pearson Islands.[2]

It consists of one land mass with two relatively smaller peaks rising out of the sea in an arc extending to the south east via a spit of rock connected to its most southerly point. The arc encloses a bay known as “Anchorage Cove” which is sheltered from the weather both from the west and the south and which can be respectively used as an anchorage and as a landing point. The three parts of the island are informally referred to in one source respectively as the “north section”, the “middle section” and the “south section”. A unnamed rock which is permanently dry is located immediately west of the "south section" of Pearson Island.[3][4][5][6]

The island has an area of 213 hectares (530 acres).[1] Its highest point is a feature called “Hill 781” with a height of 238 metres (781 feet) above sea level and which is located in the south west end of the North section and which is named after its height in the imperial unit of measurement. “Hill 781” and two other hills, “North Hill” and “East Hill” on the “north section” are of a height greater than 200 metres (660 feet) while the highest point on the remainder of the island is “South Hill” on the “south section” with a height of 115 metres (377 feet).[6][7]

The “north section” has two valleys - one opening onto a bay to the north known as “East Cove” while the other valley opens onto an unnamed cove on the east side of the island. Each is enclosed on one side by the ridge line on the west side of the island that connects “North Hill” and “Hill 781” and by a ridge line that connects “Hill 781” to “East Hill”. Each valley has a drainage system which drains into a creek which are respectively known as “North Creek” and “Main Creek”.[7][8]

Formation, geology and oceanography
Further information: Pearson Isles § Formation, geology and oceanography

Pearson Island was formed along with the rest of the Pearson Isles about 10,500 years ago following the rise of sea levels at the start of the Holocene.[9]

Geologically, Pearson Island and the other members of the Pearson Isles are the summits of an inselberg partially concealed by sea level rise. Pearson Island exhibits landforms caused firstly by the formation of the inselberg and the characteristics of the granite from which it formed and secondly by the erosive and formative processes associated with the sea.[10]

Firstly, landforms associated with the formation of the inselberg and with its constituent material respectively are sheet structures and orthogonal jointing. Sheet structures which are flat or curvilinear layers of granite which have separated from the body of the inselberg due to stresses within the overall granite body.[11] The presence of orthogonal jointing within the sheet structures at right angles to the plane of the sheet structures create access for moisture into joints resulting in enlargement of the joints and the ultimate fracture of the sheet into “cubic, quadrangular or rhomboidal blocks” which can become either individual or field of free-standing granite boulders of 2–3 metres (6 feet 7 inches–9 feet 10 inches) in height.[12]

Secondly, the action of the sea has resulted in the erosion of the “lower inclined sheet structures” on the west side of the island at sea level resulting in the formation of a steep cliff face when compared to the relatively flat profile of the east side of the island. The eastern side of the island including the coastline of “Anchorage Cove” has layers of an aeolianite limestone up to 6–9 metres (20–30 feet) above the present sea level which suggests that sea level was higher at some time in the past.[13]

The waters around Pearson Island fall to water depths greater than 50 metres (160 feet) within 500 metres (1,600 feet) from the island’s coastline.[4][14]

Flora and fauna

Flora

As of 1996, at least six plant associations are reported as being present on Pearson Island.[15]

Firstly, the parts of the island above the height of 100 metres (330 feet) above sea level support a woodland of sheoak where both shelter and soil is present. The woodland’s density increases with altitude with the result that individual sheoaks will reach a height of 3 metres (9.8 feet) and support an understorey of species such as dryland tea tree, ruby saltbush and rock fern.

Secondly, below the altitude of 100 metres (330 feet), two Melaleuca species, dryland tea tree and swamp paperbark, are present as thickets with the former species being reported as the “most widespread” of the two species.

Thirdly, a scrub of swamp paperbark is present along the Main Creek watercourse in the eastern valley where favourable conditions such as “highly saline” soil and the shelter provided by the valley are present. Areas of the island close to its coastline have a heath cover.

Fourthly, where the soil is granitic in origin, the heath is dominated by twiggy daisy-bush with sub-ordinate species such as common correa and shore westringia.

Fifthly, grey saltbush dominates in the limestone-derived soils while marsh saltbush is present in both soil types.

Sixthly, a herbfield featuring both karkalla and Austral stork's bill and fringed with round-leaved pigface is found on “the thinnest, most exposed soils on top of granite outcrops fronting the sea”.

Fauna
Peninsula Dragon on Pearson Island
Sea Lion Mother and Cub on Pearson Island
Top of Pearson Island and Pearson Island Rock Wallaby

Vertebrate animals observed on Pearson Island consist of mammals, birds and reptiles. An account from 1911 mentioned seals, Cape Barren geese, and a raptor's nest at the island's summit made from a ton of sticks. Some members of the visiting party hunted the Pearson Island rock wallaby, while another inspected the island's small lizards. An "abundance of seals" was noted, and some oystercatchers (then known as "redbills") were seen. Australasian snapper, Western blue groper and rock cod were caught in adjacent waters.[16] Arthur Searcy recalled catching 30 and 40 lb groper there.

As of 1996, the following mammals have been observed - Pearson Island rock-wallaby, bush rat and a breeding colony of Australian sea lion.[17] The Australian sea lion, previously known as the "hair seal" has been seen on the island since the early 20th century.[18][19]

As of 2006, the following birds have been observed - Richard's pipit, wedge tailed eagle, white-faced heron, eastern reef egret, ruddy turnstone, masked woodswallow, galah, red-necked stint, Cape Barren geese, Horsfield's rufous tailed, Australian raven, white-fronted chat, crimson chat, rockhopper penguin, Australian kestrel, white bellied sea eagle, welcome swallow, silver gull, Pacific gull, singing honeyeater, budgerigah, rock parrot, golden whistler, osprey, house sparrow, red-capped robin, red-tailed tropicbird, great cormorant, white-browed scrubwren, crested tern, common starling, hooded dotterel, barn owl, masked plover, silver eye and breeding colonies of fairy tern, little penguin and sooty oystercatcher.[20]

As of 1996, the following reptiles have been observed - marbled gecko, four-toed earless skink, peninsula dragon and four-toed earless skink.[21]

Pearson Island rock-wallaby

Pearson Island rock-wallaby (Petrogale lateralis pearsoni) is a sub-species of the black-footed rock-wallaby which became isolated on what is now Pearson Island by sea level rise about 10,500 years ago. Specimens were first collected by F Woods Jones in 1920 and described as a new species in 1922. It was subsequently re-described as a sub-species of the black-footed rock-wallaby. The rock-wallabies originally occupied the “north section” of the island until 1960 when six specimens were accidentally released onto the “middle” and “south” sections of the island. By 1976, the six specimens had reproduced into a population estimated at 150 individuals compared with a population on the “north section” estimated between 250 and 300 in 1975. In 1974 and 1975 respectively, groups of rock-wallabies from the "north section" of Pearson Island were transferred to Thistle Island and Wedge Island in Spencer Gulf where the populations are reported in 2008 as being respectively 500 and 200 individuals.[22][23][24][25] Previous experiments had been undertaken with the support of Captain P. Weir and Captain George Justice, who relocating pairs of wallabies to Liguanea, Price, Greenly and Four Hummocks islands.[26]

Little penguin

Little penguins were mentioned as being present on Pearson Island as early as 1914[27] and were described as "plentiful" in 1923.[28][29] In 1933, J. T. Mortlock wrote that he saw "a good many" penguins on Pearson Island.[30] In 2006, the population of the little penguin colony on Pearson Island was estimated to be 12,000 birds, making it the largest single colony in South Australia. As of 2011, the Pearson Island colony's status was unknown.[31] In 2013, a tour operator based on Kangaroo Island visited the island and reported that the little penguins were "missing".[32] A little penguin survey was scheduled to be conducted on Pearson Island by the South Australian Research and Development Institute (SARDI) in 2013.[33] As of March 2014, the SARDI survey's results remain unpublished.

History

European discovery

Pearson Island is part of the island group which was first sighted by Matthew Flinders on Saturday, 13 February 1802 and subsequently named by Flinders on the same day as the Pearson Isles.[34]

Naming of the island
Further information: Pearson Isles § Nomenclature

The name of island derived from that of the group. While the name is widely used, it is not officially named.[3][35] It also is referred to as the “North Island” within the context of the Pearson Isles by a number of sources.[3][35]

Agricultural and other economic use

Pearson Island was briefly used for the grazing of sheep in the 19th century by Anton Schlink, who had leased nearby Flinders Island for the same purpose, however, with unsuccessful results due to the island’s “unfavourable, rocky and dry nature” and difficulties with stock management.[36][37] The waters immediately adjoining the island have been used for commercial fishing, recreational fishing and recreational diving.[38]

Scientific research

Pearson Island has been the subject of scientific interest since the early twentieth century in respect to its geology, its ecology and its terrestrial and marine flora and fauna. The island and its companions are an attractive destination for scientists because of their relative remoteness, the relative low human impact and the absence of introduced pests.[21][39]

While first sighted in 1802 by Flinders, the island group was not visited by Robert Brown, the botanist accompanying Flinders, and the literature suggest that it was not visited by any of the scientists accompanying the Baudin expedition visited the island to make observations.[35]

Pearson Island was first visited by Edgar Waite, the then director of the South Australian Museum in 1914 followed by F Woods Jones, the then chair of anatomy at the University of Adelaide in 1920.[40]

The island was then the subject of three expeditions organised by the Royal Society of South Australia (RSSA) in the years 1923, 1960 and 1969. The 1923 expedition was funded by Sir George Murray, the then chief justice of Supreme Court of South Australia and led by F Woods Jones. The 1960 expedition was led by T. D. Campbell, anthropologist and a former Professor of Dentistry at the University of Adelaide. The 1969 expedition was a joint project conducted in conjunction with the then Department of Fisheries and Fauna Conservation and was led by scientists Scoresby Shepherd and I.M. Thomas.[40][41]

The most recent expedition discussed in the literature is an expedition organised by the then Department of Environment and Heritage in 2006 to visit islands within the Investigator Group including Pearson Island and included a range of personnel from various government agencies including archaeologists, botanists, geologists and zoologists.[42][43]

A navigation aid has been located on the middle section of Pearson Island since 1968. It consists of a 2 m (6 ft 7 in) high tower with a group flashing light placed at a height of 79 m (259 ft) above sea level. The land on which the aid is located is owned by the Australian Maritime Safety Authority (AMSA) which is the Australian government agency responsible for navigation aids. Access to the island for the maintenance of the navigation aid is via helicopter.[21][44][45][46][47][48]

Protected area status
Further information: Investigator Group Wilderness Protection Area

Pearson Island first received protected area status as part of the Pearson Isles on 27 July 1916 as part of a bird protection district declared under the Birds Protection Act 1900 and the Animals Protection Act 1912, to protect the black-footed rock wallaby.[49]

The Pearson Isles were subsequently proclaimed as part of a fauna reserve declared under the Fauna Conservation Act 1964 either on 1 September 1966 or 16 March 1967.[50][51] The island and other members of the group became part of the Investigator Group Conservation Park proclaimed under the National Parks and Wildlife Act 1972 in 1972 to "protect delicate island ecology and Australian sea lion and New Zealand fur seal haul-out areas”. On 25 August 2011, it and the rest of the Pearson Isles were excised from the Investigator Group Conservation Park to form the Investigator Group Wilderness Protection Area.[51][52]

Since 2012, the waters adjoining Pearson Island have been part of a sanctuary zone in the Investigator Marine Park.[53]

See also

Citations and references

Citations
  1. Robinson et al, 1996, page 196
  2. DMH, 1985, chart 38
  3. Sailing Directions (Enroute), Pub. 175: North, West, and South Coasts of Australia (PDF). Sailing Directions. United States National Geospatial-Intelligence Agency. 2017. p. 179.
  4. RAN, 1979
  5. DEH, 2006, page 5
  6. RSSA, 1971, page 124
  7. Robinson et al, 1996, page 31
  8. Robinson et al, 1996, page 196-197
  9. Robinson et al, 1996, Page 11
  10. RSSA, 1971, page 123
  11. RSSA, 1971, pages 123, 125 and 126
  12. RSSA, 1971, pages 126-128
  13. RSSA, 1971, pages 128-129
  14. Baker (Part 2), 2004, page 59
  15. Robinson et al, 1996, pages 33 & 198
  16. "A ROMANTIC LAND". Register (Adelaide, SA : 1901 - 1929). 15 February 1911. p. 8. Retrieved 9 July 2020.
  17. Robinson et al, 1996, page 199
  18. "A TRAWLING CRUISE". Observer (Adelaide, SA : 1905 - 1931). 31 October 1914. p. 22. Retrieved 9 July 2020.
  19. "LONELY ISLAND". West Coast Sentinel (Streaky Bay, SA : 1912 - 1954). 20 January 1923. p. 3. Retrieved 9 July 2020.
  20. DEH, 2006, pages 65-71
  21. Robinson et al, 1996, page 200
  22. Robinson, 1980, page 95
  23. Lennon, 2011
  24. Robinson et al, 1996, page 101
  25. Burbidge, A.; Woinarski, J.; Reed, J.; van Weenen, J.; Moseby, K.E.; Morris, K. (2008). "The IUCN Red List of Threatened Species - Petrogale lateralis". IUCN Red List of Threatened Species. 2008. Retrieved 4 June 2015.
  26. "ISLANDS OF THE WEST COAST". Register (Adelaide, SA : 1901 - 1929). 2 September 1925. p. 5. Retrieved 9 July 2020.
  27. "A TRAWLING CRUISE". Observer (Adelaide, SA : 1905 - 1931). 31 October 1914. p. 22. Retrieved 9 July 2020.
  28. RSSA, 1923, pages 119 and 122
  29. "A SCIENTIFIC HOLIDAY". Saturday Journal (Adelaide, SA : 1923 - 1929). 22 December 1923. p. 16. Retrieved 9 July 2020.
  30. "VISIT TO PEARSON ISLANDS". Port Lincoln Times (SA : 1927 - 1954). 7 April 1933. p. 2. Retrieved 23 May 2020.
  31. Wiebken, 2011, pages 11-13
  32. Winter, Caroline (27 July 2013). "Little Penguin decline hits SA tourism". Australian Broadcasting Corporation. Retrieved 25 March 2014.
  33. Delaney, Jarrad (24 July 2013). "Search for penguins". West Coast Sentinel. Retrieved 24 July 2013.
  34. Flinders, 1814 (1966), page 223
  35. RSSA, 1923, page 97
  36. Robinson et al, 1996, page 191
  37. "A pastoral pioneer, Anton Schlink". West Coast Sentinel (Streaky Bay, Sa : 1912 - 1954). West Coast Sentinel. 22 July 1927. p. 4. Retrieved 16 April 2015.
  38. Baker (Part 2), 2004, page 69
  39. Baker (Part 3), 2004, Page 51
  40. RSSA, 1971, page 120
  41. Brown, Tasman; Rogers, Ruth. Campbell, Thomas Draper (1893–1967). National Centre of Biography at the Australian National University. Retrieved 29 May 2015.
  42. Chalmers, 2006, page 40
  43. Robinson et al, 2008, pages 45-50
  44. Robinson et al, 1996, page 129
  45. Australian Lighthouses, 2015
  46. DEH, 2006, page 38
  47. BIA, 2005, page 220
  48. WAC, 2013, page 16
  49. Robinson et al, 1996, page 138
  50. Robinson et al, 1996, page 140
  51. DEH, 2006, page 6
  52. WAC, 2013, pages 16-17
  53. DEWNR, 2012, page 22 of 26

References
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