Division Table 1. Cyclones passing over or close - Pulu Keeling National Park Management Plan - Table 1. Cyclones passing over or close to the Cocos (Keeling) Islands | Zoe
Located in the Indian Ocean (lat. 12° 12’S, long. 96° 54’E), the Cocos (Keeling) Islands [Figure 1] are approximately 2900 kilometres north-west of Perth, 975 kilometres west-south-west of Christmas Island and 1,000 kilometres south-west of Java Head. They are located in one of Australia’s most distant and isolated Territories. The Cocos (Keeling) Group consists of 27 separate islands, the land area of which totals some 14 square kilometres [Figure 2].
The island group comprises two separate atolls, the southern, inhabited atoll of 26 islands, and the northern atoll (North Keeling Island - a single horseshoe-shaped island), which is located 24 km to the north of the southern group (lat. 11° 50’S, long. 96° 49’E). The atolls are connected by a submerged ridge at a depth of 700-800 metres. Together they comprise a single feature rising from the surrounding ocean floor.
Pulu Keeling National Park was proclaimed in December 1995 and is Australia’s sixth and smallest Commonwealth national park. ‘Pulu’ is the Cocos-Malay word for island. The Park includes the 1.2 square kilometre land area of the island, the central lagoon, and the waters around the island extending out to 1.5 kilometres from the high water mark.
History
Cocos (Keeling) Islands
The island group is named after the coconut, Cocos nucifera, which grows in profusion, even before the deliberate planting of almost all of the southern atoll as a part of the Clunies-Ross estate.
Captain William Keeling of the Dutch East India Company is believed to have been the first European to sight the islands in 1609 on his return from Bantam in the Dutch East Indies, though there is no record of that sighting.
In his 1805 sailing directory for this region of the Indian Ocean, the British hydrographer, James Horsburgh, called these atolls the Cocos-Keeling Islands, and named one of them after himself. After settlement the early inhabitants called them the Borneo Coral Reefs after the supply vessel, the Borneo, owned by John and Joseph Hare and Co, and captained by John Clunies-Ross. They were also known as the Keeling-Cocos Islands until 1955, when they officially became the Cocos (Keeling) Islands.
Despite knowledge of the existence of these islands for 200 years or more, it was not until the early nineteenth century that they were settled. Interest developed because they were situated on a trade route from Europe to the Far East. The first settlement was accidental; Captain Le Cour and the crew of the ship Mauritius lived on Direction Island in the southern atoll for several weeks after they were wrecked on the reef in 1825.
On 6 December 1825, Captain John Clunies-Ross, a Scottish trader sailing the Borneo for Alexander Hare’s company, made a brief landing on the islands. In the following year a settlement was established by Alexander Hare. John Clunies-Ross and his family returned in 1827 with the intention of commencing a settlement on the islands.
The history of this time is particularly colourful. The relations between Ross and Hare were poor. Initially both claimed ownership of the islands, but in 1831 Hare finally left the atoll. The Clunies-Ross family, who became known as the ‘Kings of the Cocos’, reigned over the islands for more than 150 years (Hughes 1950). Their family papers contain detailed information on the history and use of the islands during this time.
In 1857, the islands were declared a part of the British Dominions by Captain Fremantle who arrived aboard H.M.S. Juno, having misread his directions which instructed that he annex another Cocos Island in the Andaman Islands (Gibson-Hill 1947). In 1886 Queen Victoria granted in perpetuity all of the islands, under certain provisions, to John George Clunies-Ross. Responsibility for supervision of the islands was transferred over the years to the Governments of Ceylon (1878), the Straits Settlements (1886), Singapore (1903) and Ceylon once again (1939-45). They became a Territory of the Commonwealth of Australia in 1955, and in 1978 Australia purchased all of the lands, excepting the family home, from the Clunies-Ross family for $6.25 million. The family home and the Clunies-Ross collection of historic books, documents, furniture and paintings were purchased by the Australian Government in 1993 for $1.2 million. In 1984, through the United Nations supervised Act of Self Determination (ASD), the Cocos-Malay population voted to integrate with the Australian community. The ASD process instigated a commitment by the Commonwealth to raise services and standards of living to comparable Australian levels within 10 years (Carlsen 1995).
The Territory is administered by the Australian Government Department of Transport and Regional Services.
There are about 460 Cocos-Malay people living in the kampong (settlement) on Home Island. The population of Home Island predominantly descends from Malay workers brought to Cocos to work in the coconut plantations established by the Clunies-Ross family in the 1830s. These Cocos-Malays have developed a unique culture based on Muslim beliefs, and have colourful celebrations for events such as Hari Raya and weddings.
About 100 people live across the lagoon on West Island. They are mostly Government employees, contractors and their families.
North Keeling Island
The Cocos (Keeling) Group is named after Captain William Keeling. It was sketched, showing coconuts, by the Swedish captain Ekeberg in 1749 and appears on the 1787 chart reproduced by Dalrymple, the British hydrographer. Fitzroy examined and mapped it from H.M.S. Beagle in 1836, but made no landing.
North Keeling Island has not been inhabited for any extended period and is in a natural state. Fortunately, its remoteness from the main atoll, its difficult landing area and the absence of a reliable, fresh water supply have combined to preclude any possibility of permanent settlement. Nevertheless, small groups of Cocos-Malay boats have been paying occasional visits to this island almost every year since the early days of the occupation of the southern atoll. These hazardous voyages were usually made to collect coconuts, timber and seabirds (Bunce 1988).
Late in the nineteenth century, small camps of beri-beri sufferers lived on the island for short periods. Malay graves near the southern shore of the island mark the final resting place of a woman and a girl who succumbed to this dietary deficiency, and a male (also suffering from beri-beri), who died in an accident (Bunce 1988).
In November 1914 the German light-cruiser SMS Emden ran aground on the windswept southern reef of the island after her unsuccessful encounter with HMAS Sydney. Not all of the survivors were prepared to give themselves up and a handful hid on the island. In October 1915 a work gang from Home Island on the southern atoll found a number of their skeletons, which they buried on the shore near the wreck (Gibson-Hill 1948).
From October 1915 to January 1916, the islanders salvaged what they could from the German ship. Anything detachable and portable was removed and transported back to the landing area by trolleys that ran on narrow railway lines. The stripped hulk later slipped back off the reef into deeper water after a cyclone (Gibson-Hill 1948).
In 1950 a Japanese salvage company removed as much of the hull of the Emden as they could and shipped it back to Japan (Bunce 1988).
Between the wars, groups of 20 Cocos-Malay workers were stationed on North Keeling Island for up to 2 weeks at a time. These parties would live in atap (long-houses), built on the western shores of the lagoon. Once or twice a week they would receive a visit from an estate vessel, which would deliver foodstuffs and water and return to Home Island with timber, coconuts and birds (Bunce 1988).
After the death of John Sydney Clunies-Ross in 1944, the frequency of seabird hunting trips to North Keeling Island increased considerably. Groups of jukongs (small sailing boats) would go whenever the weather was suitable and thousands of birds would be brought down with shotguns as well as traditional flails. Barges would travel to the island once or twice a year to gather coconuts or bring back birds for Hari Raya festivities (Bunce 1988). All access to North Keeling Island was under direct supervision of the Clunies-Ross family. After the Government purchased the islands people were required to obtain a permit from the Shire Council prior to visiting North Keeling.
In the late 1970s and early 1980s, the acquisition of more efficient boats and weapons by the Cocos-Malay people greatly increased the frequency and efficiency of bird-hunting on North Keeling Island (Stokes 1994). In 1982, the Australian National Parks and Wildlife Service (ANPWS), now Parks Australia, investigated the situation and recommended urgent control of hunting (Stokes et al. 1984).
By July 1986, agreement had been reached with the Cocos-Malay people for a seabird hunting moratorium on North Keeling Island and the institution of a quota system of hunting from Horsburgh Island. The conclusion of the 1986 seabird hunting agreement resulted in considerable praise for the Cocos-Malay community, by the Australian and international community.
Cyclone John devastated the red-footed booby population in 1989 and all legal hunting ceased, to allow the population time to recover. In October 1992, Part 3 of the National Parks and Wildlife Regulations (made under the National Parks and Wildlife Conservation Act 1975) came into operation and provided protection for the red-footed booby and other species in the Cocos (Keeling) Islands Territory. Under the Regulations, any harvest of red-footed boobies had to be in accordance with a wildife management program approved by the Director of National Parks. Part 3 of the National Parks and Wildlife Regulations ceased to apply to North Keeling Island when it became part of Pulu Keeling National Park in December 1995. However, in 1996 a wildlife management program was approved in relation to the rest of the Territory, following the independent assessment of Kentish and Ryan (1996), which concluded that the red-footed booby population had returned to the levels preceding Cyclone John.
Under the wildlife management program, two harvests of red-footed boobies were approved in 1996 and 1997, but no hunting took place, possibly because the method of harvest allowed under the program involved using a flail, and not firearms. Lack of access to Pulu Keeling National Park in 1998 and 1999, due to unavailability of a suitable vessel, prevented monitoring of the red-footed booby population required by the wildlife management program. Consequently, approval of a harvest in those years was not possible. In July 2000, the National Parks and Wildlife Conservation Act 1975 was replaced by the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Red-footed boobies, Sula sula, are listed as a migratory species under the new Act and are under the protection of the Act. Any further harvest will be subject to the environmental assessment and approval provisions of the EPBC Act.
Pulu Keeling National Park
The Cocos (Keeling) Islands became an Australian External Territory on 23rd November 1955. In 1984, the Commonwealth handed over most of the land of the Cocos (Keeling) Islands to the Cocos (Keeling) Islands Shire Council, to be held in trust for the people of the islands. This trust deed stipulated that North Keeling Island was to be managed to conserve, amongst other things, the unique flora and fauna of the island.
The conservation significance of North Keeling Island was clearly recognised when it was recommended to become a national park or nature reserve by two House of Representative committees in 1990 and 1991, and when the island was listed on the Register of the National Estate in 1990.
In mid 1993, the Cocos (Keeling) Islands Shire Council decided, in principle, to lease North Keeling Island to the Commonwealth for the creation of a national park. This lease was signed by the Commonwealth and the Cocos (Keeling) Islands Shire Council in January 1995. Pulu Keeling National Park, comprising North Keeling Island and surrounding waters for a distance of 1.5 kilometres, was declared by Proclamation under the National Parks and Wildlife Conservation Act 1975 on 12 December 1995. The Commonwealth’s interest as lessee of North Keeling Island passed to the Director of National Parks in accordance with the Act.
The National Parks and Wildlife Conservation Act 1975 was replaced in July 2000 by the EPBC Act. The Proclamation of Pulu Keeling National Park continues as if it had been made under Section 344 of the EPBC Act so that the area continues as a Commonwealth reserve under the EPBC Act, for the following purposes:
the preservation of the area in its natural condition; and
the encouragement and regulation of the appropriate use, appreciation and enjoyment of the area by the public.
The Proclamation of Pulu Keeling National Park [Figure 3 and Appendix 6] was an important event that will help ensure the long-term conservation of the unique biodiversity and historical values of the Park, for the benefit of both the Cocos-Malay community and the wider local, national and international communities.
Physical Geography
Geology
The Cocos (Keeling) Islands consist of two separate coral atolls, 24 km apart, which have formed atop an old volcanic seamount that rises from a depth of 5,000 m in the north-eastern Indian Ocean. Bathymetric research shows that the atolls’ foundations are actually two of a series of undersea features known as the Vening-Meinesz Seamounts. This range of mountains also includes Christmas Island and extends in a north-easterly direction from a prominent seafloor feature of the Indian Ocean known as the Ninetyeast Ridge. The atolls of the Cocos (Keeling) Islands are two peaks in a section of the range known as the Cocos Rise (Jongsma 1976).
The two atolls are connected by a narrow submarine bank at a depth of 700-800 metres (Gibson-Hill 1948). Approximately 100 kilometres south-west of Cocos lies the Umitaka-Mary or Muirfield Seamount which rises to 16 metres below the surface of the ocean. Taken as a series from Umitaka-Mary in the south-west to Christmas Island in the north-east, these seamounts display a sequence in the evolution of atolls. Over the last 100 million years the Indo-Australian plate has moved steadily north towards the Java Trench. As it has done so it has passed over a ‘hot spot,’ or plume rising from deep in the mantle, producing a chain of seamounts with a south-west to north-east trend. Sediments on the Cocos Rise are very thin (100 metres to 200 metres thick) and no mineralisation or accumulation of petroleum has occurred (Jongsma 1976).
The Cocos (Keeling) Islands were the only coral atolls that Charles Darwin visited in 1836 as he developed his well-known theory of coral atoll formation (Darwin 1842), in which he asserted that the upgrowth of coral reefs continued long after the seamounts that supported them had subsided. While others including Guppy (1889) and Wood-Jones (1912) presented alternative theories, Darwin’s subsidence theory of coral reef development gained wide acceptance. The thickness of the corals underlying Cocos is not known, but the dredging of basaltic rocks in local waters suggest that it is in the order of 500-1,000 metres (Bunce 1988).
North Keeling Island is surrounded by a broken, irregular fringing reef, except at the north-west corner. Like the shingle bank around the shore of the island, the reef is narrower on the sheltered sides of the island and broader on the exposed sides. On the east coast it is continuous across the mouth of the lagoon and forms a wide bar, which at times blocks the entrance.
Geomorphology and Topography
North Keeling Island is approximately 2.0 kilometres long and 1.3 kilometres wide, with an internal lagoon, and a terrestrial area of 1.2 square kilometres above high water mark. Its shape is approximately rectangular with its long axis bearing slightly north-east. Like the southern atoll, it is a true coral island.
In form, the island is low and flat. The shore rises fairly steeply to a height of 3-5 metres, and from this peripheral ridge the ground slopes gently down to a large, shallow, sandy-bottomed lagoon which occupies the greater part of the interior [Figure 4].
The composition of the island varies from sand to rubble. On the northern shore there is a broad, sandy beach. This continues along the western shore but with varying amounts of shingle. In profile, the sandy beach rises up to about 4 metres above mean sea level. The southern shore of the island is composed of a spectacular steep shingle beach, with a series of berms, or ridges. Much of the eastern shore is composed of a series of shingle berms; these are particularly well-developed just south of the channel into the lagoon, but continue to the north as well.
There are also outcrops of coral conglomerate. A broad platform of conglomerate extends out over the reef flat at the eastern part of the island, almost closing the channel into the lagoon. Along much of the southern and eastern shore, the conglomerate outcrops occur at the foot of the beach but contain a series of parallel rubble ridges, that are dipped and stratified like beachrock.
There has been considerable speculation as to how North Keeling Island developed. The location of the remaining entrance to the lagoon is unusual because it is on the most windward side of the island, rather than in the shelter that might normally develop on the leeward. Indeed, the island is the inverse of the horseshoe shape that Guppy (1889) considered the typical style of development on the main atoll. This has led a number of observers, starting with Fitzroy (1839), to suggest that the island developed from a series of formerly unconnected islands.
Some indication of the age of the island is provided by research undertaken on the southern atoll. Samples of coral shingle from a trench through Home Island sediments, indicate an age range of 1,400-1,800 years B.P (Woodroffe et al. 1994).
Soils
The soils of North Keeling Island are calcareous and derived from coral breakdown. They comprise a relatively thin layer of sandy loam which in places grades into moderately and/or very stony sand comprising considerable amounts of coral clinker. They overlay a highly permeable sub-stratum which allows rapid leaching of nutrients. On the main (southern) atoll, long-term leaching has led to deficiencies in iron, potassium, copper, manganese, magnesium and other minerals (Cameron McNamara Consultants 1984). This leaching has probably also occurred on North Keeling Island. Similarly, the soils of North Keeling Island are expected to be highly alkaline, as on the southern atoll, with pH levels of between 8.0 and 8.5. Soils abutting the outer shore are subject to wave erosion during high tides and storm surges.
The lagoon shore of the island slopes gradually and deepens slowly. At low tide, its maximum depth is less than 2 m. The bottom, and much of the beach, is a fine, greyish, sandy silt, much of which is derived from decaying vegetation. Towards the eastern recesses, this is greyer and darker and in the north-east corner, the beach is composed of a fine, dark, brownish mud. In a few places, particularly towards the southern end, the sand is replaced by a bare breccia slope and jagged fragments occur all down the west side.
Along the sheltered sides of the island, the shore is composed partly of coral shingle and partly of patches of white sand. However, periodic storms and changes in wave alignments alter the distribution of beach sand on an annual cycle. On the south and east coast (the windward sides) the bank is almost entirely coral shingle.
Hydrology
The water resources of the Cocos (Keeling) Islands consist essentially of groundwater and rainwater. Where conditions are favourable, fresh groundwater on coral islands occurs in the form of shallow freshwater lenses beneath the ground surface. Such lenses are found in some of the larger islands within the Cocos (Keeling) Group. The groundwater from these lenses is the major source of freshwater for potable and other uses, on both Home and West Islands (Falkland 1994).
Due to the generally porous nature of the soils and underlying geology, there is no significant surface run-off. Run-off only occurs in localised areas where the ground is compacted and only for very short periods after heavy rain.
The upper surface of a freshwater lens is the water table and the lower surface is a boundary between freshwater and saline water. The lower boundary is not a sharp interface but is in the form of a transition zone. Within the transition zone, over the space of a few metres, the water salinity increases from freshwater to seawater (Falkland 1994).
The size and salinity distribution of freshwater lenses, particularly the depth of freshwater and transition zones, are dependent on many factors including: rainfall; the amount and nature of surface vegetation; the nature and distribution of soils (these factors influence the evapo-transpiration); and the island’s size, particularly the width from sea to lagoon (Falkland 1994).
Preliminary investigations on North Keeling Island (Falkland 1988, 1992) indicate the presence of a very thin freshwater lens on at least part of the island. It is not known whether this lens is permanent.
Gibson-Hill (1948) states that the North Keeling Island wells were sunk to a depth of 3.6-4.5 metres, before the Second World War, when between 40 and 60 Cocos-Malay people lived there for up to 3 months at the end of each year, collecting coconuts and timber. The water in the wells then was reported to be brackish, though not heavily salted, and was used for washing and cooking rather than drinking.
The broader western side of the island is an average 300-400 metres wide. This roughly equates to the minimum 400 metre width of larger islands on the southern atoll, which is necessary to sustain a freshwater lens on tidally-influenced saltwater (Jacobson 1976).
Climate
The climate of North Keeling Island appears to correspond closely with that of the southern atoll of the Cocos (Keeling) Islands.
The Cocos (Keeling) Islands are situated in the humid, tropical zone, at the southern edge of the equatorial low pressure belt which moves northwards and southwards according to the season. The islands are subject to the north-west monsoons of January to May, which are moderated by oceanic conditions. Relatively strong, constant south-east trade winds blow for much of the year, both during and outside the monsoon season.
The main climatic features of the islands are:
annual rainfall varying between about 840 and 3,290 mm with an average of 1,976 mm per annum;
annual potential evaporation of about 2,000 mm with an average daily evaporation of 6.7mm;
relatively uniform temperatures with an average daily maximum temperature of 28.9°C and average daily minimum temperature of 24.4°C;
relative humidity ranging between about 65% and 90% with a mean of 75%;
mean daily surface pressure of approximately 1011 hPa. Extremely low pressure values may, however, be recorded during the passage of tropical cyclones;
prevailing winds from the east to south-east for all months, showing the influence of the south-east trade winds; and
mean, daily wind speeds that vary from approximately 16 to 30 km/hr with a maximum gust during a cyclone recorded at 176 km/hr.
Cyclones
Cyclones have the potential to have serious effects on the vegetation and wildlife of the island. A cyclone database maintained by the Bureau of Meteorology shows that a number of cyclones have affected the Cocos (Keeling) Islands. One of the most damaging cyclones in recent times was ‘Doreen’, which passed directly over the southern atoll in 1968. Cyclone Walter (April 2001) destroyed 61 per cent of the canopy and 14 per cent of the trees. The fledged chicks from the previous year also disappeared (Murray pers. comm. 2001).
Table 1 lists those cyclones that have passed over or close to Cocos (Keeling) Islands since 1960.
Terrestrial Environment
Flora
North Keeling Island is a very remote isolated oceanic island that has always been isolated from any large land mass. Before it was first visited by people, colonisation of the island by plants and animals could have occurred only by wind, pelagic drift, flight or animal carriage. The origins and development of the flora and fauna of the island into a unique assemblage of ‘travelling’ species has long fascinated biologists.
In terms of geological substrate and elevation, the Cocos (Keeling) Islands have similarities with some of the islands of the central and western Indian Ocean for example, the Maldives and the Farquhar Group. All of these low islands have evolved in isolation from a continent, through the combined forces of vulcanism, subsidence and coral growth. They all now rise less than 10 m above sea level (Williams 1994b). The low habitat diversity of these islands leads to a flora characterised by very low endemicity with indigenous taxa of pan-tropical or Indo-Pacific distribution dominating (Renvoize 1979).
The Cocos (Keeling) Islands are no exception to this general pattern, with only one endemic sub-species of plant, Pandanus tectorius cocosensis (Renvoize 1979). Sixty-one plant species have been recorded on Cocos (Keeling) Islands. North Keeling Island has a number of species not found on the southern atoll. Some species are more abundant on North Keeling Island than on the islands of the southern atoll, either because of greater areas of suitable habitat on North Keeling Island or due to clearing over the last 160 years on the southern atoll (Williams 1994a). Other species on North Keeling Island have a restricted distribution and most of these are found on the northern peninsula at the entrance to the lagoon on the north west shore and adjacent habitats.
The vegetation of North Keeling Island was divided into four zones by Gibson-Hill (1948); (1) pisonia, Pisonia grandis, and coconut, Cocos nucifera, forest; (2) octopus bush, Argusia argentea, shrublands; (3) tea shrub, Pemphis acidula, thickets; (4) and open grassy areas. Much of the island is dominated by the pisonia forest, mixed in many areas with coconut, with a few stands of pure coconut also occuring [Figure 4].
Octopus bush is common on the eastern shore, dominating the crest of the shingle or rubble ridges. In some cases it forms monospecific stands while north of the lagoon entrance it occurs with cabbage bush, Scaevola taccada. Around the margins of the lagoon, tea shrub forms dense thickets, replaced in some places by ironwood, Cordia subcordata. The open grassy areas often have a covering of sea purslane, Sesuvium portulacastrum, such as the clearing to the north-west of the lagoon.
The richest floristic units, apart from the herblands, are the forest types found near the lagoon entrance and on the north-west side of the island.
Table 2 lists native plants, exotic species and plant species with restricted distribution on North Keeling Island.
Fauna
Like the flora, the fauna of the Cocos (Keeling) Islands emanates from a number of locations. While no mammals exist on the island, land crabs are conspicuous on the forest floor, seabirds are prolific with many species breeding, and there are a host of small invertebrates present. Appendix 1 details fauna of the Park which are listed under the EPBC Act and International Agreements.
Terrestrial Vertebrates
The only terrestrial vertebrates recorded from North Keeling Island are birds, the gecko Lepidodactylus lugubris, and rabbits, Oryctolagus cuniculus. The gecko is relatively uncommon (Stokes and Cogger 1987), while the rabbit was an early introduction that had disappeared by the 1880s (Guppy 1890). North Keeling Island has never been colonised by rats.
Birds
Table 4 lists the birds recorded for the Park and the whole of the Cocos (Keeling) Islands.
When Charles Darwin visited the Cocos (Keeling) Islands in April 1836, the ‘immense number’ of marine birds recorded in 1828-29 on the main atoll (cited in Gibson-Hill 1949) were probably somewhat diminished. Darwin however refers to trees on the southern atoll being occupied by many nests of gannets [sic], frigate birds and terns, and to a smell in the air which led him to call it a ‘sea rookery’ (Darwin 1979). From Darwin’s diary, it would appear that the forest of the southern atoll was by then well on the way to being transformed into the monoculture coconut plantation that it had become by 1885, when most birds had been eliminated from the southern atoll (Forbes 1885). The reason for this decline was almost certainly due to habitat change, intense hunting and predation by cats and rats. Today, there are still very few birds on the southern atoll.
Birds remain in large numbers on North Keeling Island due to its isolation, the difficulty of landing, the absence of any feral predators and access restrictions placed by the former Clunies-Ross family up to the mid 1970s (Stokes 1994).
Of the approximately sixty species of birds recorded from the Cocos (Keeling) Islands, twenty-five have been seen on North Keeling Island in the last twenty years. Of those twenty-four, fifteen breed on the island, possibly sixteen if the Round Island petrel, Pterodroma arminjoniana, is confirmed to breed there. All species recorded from North Keeling Island are protected by the EPBC Act, being listed threatened species (critically endangered, endangered or vulnerable), listed migratory species or listed marine species under the Act.
North Keeling Island is also one of the few remaining near-pristine tropical islands in the Indian Ocean (Stokes et al. 1984), and is the only seabird breeding colony within a radius of 975 kilometres. Unsurprisingly, therefore, the island is the focal bird habitat within a huge expanse of the central-eastern Indian Ocean. It is unlikely that any other Indian Ocean island rivals North Keeling’s range of seabird species (Feare 1984; Stokes and Goh 1987). However, the health of many of the island’s seabird species is largely unknown, with careful management is required to avoid the decline in seabird populations seen on other Indian Ocean islands over the last 100 years.
By far the most numerous seabird on North Keeling Island is the red-footed booby Sula sula. Based on comprehensive population surveys between 1985 and 1996, the current population is estimated at approximately 30,000 breeding pairs (Baker 2003, pers comm.), making it one of the most important and possibly the largest colony of red-footed boobies in the world. Although the red-footed booby is the most numerous booby species in the world, most populations are threatened by habitat destruction and feral animals (Marchant & Higgins 1990).
Gibson-Hill (1948) estimated there were only 3,500-4,000 pairs of breeding red-footed boobies in July 1941. The main Pisonia community on the western margin of the island, which now supports the major concentration of nesting red-footed boobies, was apparently devoid of nests at the time of Gibson-Hill’s visit. Large numbers of birds of all ages have been harvested by Cocos-Malays over the last century, and this undoubtedly had a significant effect on the population status. Protection of the population on North Keeling Island in more recent years has resulted in a much larger and more stable population, although still vulnerable to cyclones.
Least and great frigate birds, Fregata ariel and F. minor, also occur on the island in large numbers. Data from surveys indicates a population size of possibly 3,000 breeding pairs of least frigate birds, with a smaller number of great frigate birds. North Keeling Island, therefore, has the second largest population of least frigate birds in Australia and probably in the Indian Ocean. Numbers of these two species have also been depleted by past harvesting and on-going poaching (Murray 2003, pers comm.).
The Cocos buff-banded rail, Gallirallus philippensis andrewsi, is significant as the only endemic bird in the Territory. It is a common bird on North Keeling Island and occurs in all habitats. It frequently forages along the lagoon shore, eating crustacea, which are abundant in the seagrass deposited along the tide line.
The status of the rail in the Territory is of concern, as it is now extremely rare on the main (southern) atoll. This is in contrast to 1906-07 when it was reported to be ‘very abundant on all the islands’ (Wood-Jones 1909). In the past the bird was widely hunted and by 1941 a decline was apparent, with reduced numbers on West and Home Islands (Gibson-Hill 1949). However, rail individuals were sighted on West and South Islands in 2002 (Murray 2002, pers. comm.).
Gibson-Hill (1948) states that a number of rails were released last century on North Keeling Island. The island now appears to support the last significant population. However, it would seem unusual for this bird not to have colonised North Keeling Island naturally as it is not far from the southern atoll and the species is well distributed through many small Pacific islands (Stokes et al. 1984).
The Round Island petrel, Pterodroma armijoniana, was listed in July 2002 as critically endangered under the EPBC Act. It breeds at fewer than five locations world-wide and is believed to have a very small population in Pulu Keeling National Park. Although Parks Australia staff have been conducting surveys, there are no confirmed recent sightings in Pulu Keeling National Park.
White-tailed tropicbirds, Phaethon lepturus, are common, nesting in moderate numbers in hollows of mature Pisonia trees.
Several species of migratory waders are occasionally seen feeding on the lagoon shoreline. The significance of the island as a staging point for migratory birds is not known.
Feral chickens, Gallus gallus, are reported to have existed on the island for many years from last century, but are now extinct (Guppy 1890; Gibson-Hill 1948).
Terrestrial Reptiles
The gecko, Lepidodactylus lugubris, has successfully colonised many oceanic islands, a success in part attributed to its ability to reproduce asexually (Cogger 1996). It is not possible to say whether the Cocos (Keeling) populations made their own way to the islands, or whether they were introduced as a result of human activity (Cogger 1996).
Invertebrates
Crabs are the most conspicuous and probably the most numerous inhabitants of the forest floor and beach fringe. The little nipper, Geograpsus grayi, is common under the Pisonia forest. The robber crab, Birgus latro, is occasionally observed within the forest but was more abundant prior to harvesting by Cocos-Malays. Three species of hermit crabs are present in large numbers, the red hermit crab, Coenobita perlata, the purple hermit crab, C. brevimana, and the tawny hermit crab, C. rugosa. During the day the hermit crabs take refuge under logs and shrubs, and at night-time venture out to scavenge on the forest floor and beach.
The land crab, Cardisoma carnifex, is abundant, particularly in the saltmarsh and on the fringes of the lagoon. The yellow nipper, Geograpsus crinipes, and the Christmas Island red crab, Gecarcoidea natalis, also occur.
The horn-eyed ghost crab, Ocypode ceratophthalma, is commonly found on the north-western beaches with Grapsus tenuicrustatis common on rocky sections of the coast.
A species of cricket, Ornebius sp., occurs among the leaves of both Cordia and Pisonia, and Nerius lineolatus, a long-legged Dipteran, and the mosquito, Aedes aegypti, are plentiful. Butterflies, ants, cockroaches, beetles and weevils are also present on North Keeling Island.
Spiders, a small wood-louse, centipedes, millipedes, termites, scorpions, various species of ectoparasitic ticks and mites, and a terrestrial mollusc Melampus sp. have been recorded on North Keeling, but as yet no earthworms have been found. Earthworms are abundant on the southern atoll.
Marine Environment
North Keeling Island is entirely surrounded by a broken, irregular fringing reef, except at the northwest corner. The reef is narrower on the sheltered sides of the island (north and west), and broader on the exposed sides (south and east). On the east coast it is continuous across the mouth of the lagoon, and forms a wide bar which effectively blocks the entrance. Much of the reef is partly exposed at low tide (Gibson-Hill 1948). Along the western side of the island is a wide coral terrace which drops into deep water (Ecology Lab 1994). It is believed there is no seagrass fringing North Keeling (Murray 2003, pers comm.).
North Keeling Island’s lagoon has only a single, narrow entrance on the south-eastern side of the atoll. The opening has no channel through the reef, but is a shallow conduit which drains almost totally at low tide (Woodroffe and McLean 1994). The lagoon is shallow, reported as being nowhere deeper than 8 feet (2.4 m) by Guppy (1889). Its surface sediments are muddy sands, except for two sandy spits which trail in through the entrance. Some of the lagoon is covered with seagrass, and is an important fish nursery area. Periodically, the lagoon entrance becomes blocked, and there is no water movement into or out of the lagoon. When this occurs the water quality in the lagoon deteriorates, and fish and seagrasses die.
In broad terms the Park comprises three major marine habitat types: (1) outer reef slope (subtidal); (2) reef flats including sandy and rocky shores (predominantly intertidal); and (3) lagoon (predominantly subtidal) (Berry 1989).
The Cocos (Keeling) atolls represent the western limit for many species of the Western Pacific biogeographic province. Biogeographic and ecological interest in the marine biota also stems from the extreme isolation and relatively small size of the atolls, from which there are some unusual absences including benthic skates and rays.
According to Berry (1989), the extreme isolation of the islands influences their faunal composition. Those species established at the Cocos (Keeling) Islands must be pelagic as adults, or have long-lived pelagic larval stages. In general, the fauna is relatively depauperate compared with other atolls (Berry 1989 ), but there is evidence of hybridisation which may ultimately result in the evolution of a new species (Choat 2003 pers. comm.). In recent times periodical large-scale natural disturbances including cyclones (Bunce 1988), deoxygenation of lagoon waters (perhaps linked to El Niño events) and outbreaks of crown of thorns starfish, Acanthaster planci, have also reduced the abundance of corals (Berry 1989).
Specific information on marine fauna surrounding North Keeling Island is limited. Taxonomic surveys of the southern atoll were undertaken by the Western Australian Museum in 1989 and the Ecology Laboratory of the Institute of Marine Ecology, University of Sydney, in 1992, with less attention given to the waters surrounding North Keeling Island due to the difficulty of access. Ongoing surveys by Parks Australia staff and researchers from James Cook University is progressively adding to knowledge on marine fauna.
Marine Mammals
Two species of dolphin are regularly seen in the Park: the common dolphin Delphinus delphis and the bottlenose dolphin Tursiops truncatus (Murray 2002, pers. comm.).
An unidentified whale has been recorded passing through the waters of the Park, and a species of beaked whale has been washed up on the southern atoll (Tranter 1995, pers. comm.). Humpback whales, Megaptera novaeangliae, and their calves have been filmed migrating past the Cocos (Keeling) Islands and there have been several sightings of Cuviers beaked whale, Ziphius cavirostris, and unidentified pilot whales. A dead sperm whale, Physeter macrocephalus, washed up on South Island in October 2003 (Murray 2003, pers comm.). A dugong, Dugong dugong, has been sighted by residents a number of times in the past ten years in the lagoon of the southern atoll, and in May 2002, one appeared to take up residency (Murray 2002, pers. comm.).
Marine Reptiles
Gibson-Hill (1950a) recorded both the hawksbill turtle, Eretmochelys imbricata, and the green turtle, Chelonia mydas, from the Cocos (Keeling) Islands. As early as 1909, Wood-Jones observed that breeding of green turtles had virtually ceased on the islands of the southern atoll, although extensive nesting could be observed on North Keeling Island. Gibson Hill (1950a) reported a similar situation in 1941. Nesting green turtles are occasionally observed on the southern atoll (Murray 2002, pers. comm.), but frequently on North Keeling Island. Although hawksbill turtles are seen and are likely to reside around the island, nesting has not been recorded (Tranter 1997, pers. comm.). Olive ridley turtles, Lepidochelys olivacea, have been seen in the Park, and loggerheads, Caretta caretta, and leatherbacks, Dermochelys coriacea, on the southern atoll (Murray 2002, pers. comm.). The only two species of sea snake recorded at the southern atoll is the yellow-bellied sea-snake, Pelamis platurus, and the banded sea krait, Laticauda colubrina.
Fish
About 528 species of fish have been recorded in the seas of the Cocos (Keeling) Islands (Berry 1989). Compared with other oceanic atolls, the islands’ fish fauna appears impoverished (Allen 1989). Reasons for this may include the small physical size of the islands, the relative isolation and lack of surrounding island ‘stepping stones’, and limited surveys of fish (Allen 1989). Most fish found at Cocos (Keeling) have distributions that cover large areas of the Indo-Pacific region (Allen 1989). However, recent genetic research has shown at least 4 species to be hybridising . This is believed to be the result of Cocos (Keeling) Islands’ location at the confluence of the western Pacific and eastern Indian Ocean biogeographic provinces (Choat 2003, pers comm.). There is no confirmed endemism in the Cocos (Keeling) Islands fish fauna, although one angelfish, Centropyge joculator, is known only from Cocos (Keeling) and Christmas Island. An undescribed goby of the genus Trimma may have the same distribution (Allen and Smith-Vaniz 1994).
Substantial populations of both butterfly fish and sharks (black-tip, white-tip and grey reef) in the Park provide a good indication of a healthy fish fauna. Whale sharks are also occasionally seen as they migrate past the atolls. Comparisons made between Cocos (Keeling) Islands and other Indo-Pacific atolls reinforce the notion of Cocos as one of the last areas of pristine reef systems in the world (Choat 2003, pers. comm.).
Table 3 lists the fish species of Cocos (Keeling) Islands.
Corals
Reef-building corals of the southern atoll have received considerable attention, partly because the southern atoll was the only one ever visited by Darwin (in 1836), and partly because of the intrinsic interest in the atoll’s geographic isolation. It is located approximately 1000 kilometres and 1,830 kilometres from the reefs of Java and Western Australia respectively, with Christmas Island being the only ‘stepping stone’ for westerly movement of propagules (Berry 1989). Many common and widespread Indo-Pacific taxa have not been recorded from the Cocos (Keeling) Islands and are almost certainly absent. Ninety-nine species of reef corals are recorded from the Cocos (Keeling) Islands (Veron 1990). Of these, all but twelve are known from Western Australia. Nine species are not recorded elsewhere in the eastern Indian Ocean and two (one being taxonomically doubtful) may be endemic (Veron 1990).
Molluscs
Six hundred and ten species of molluscs are known from the Cocos (Keeling) Islands. There are 496 gastropods, 109 bivalves, 1 chiton and 4 cephalopods. The fauna is diverse and compares favourably with the total number of species known from nearby areas that have been studied, such as Christmas Island with 490 species (Berry 1989).
Crustaceans
A total of 198 species of decapod crustaceans have been recorded with the most diverse taxa being xanthoid and paguroid crabs (Berry 1989). Three species of rock lobster, Panulirus penicillatus,
P. ornatus and P. versicolor are widespread in the Indo-Pacific area and have also been recorded at the Cocos (Keeling) Islands (Berry 1989). A total of 13 species of barnacles in 11 genera have also been recorded from the area (Jones 1994).
Eighty-nine species of echinoderms have been recorded at the Cocos (Keeling) Islands, most being widespread Indo-West Pacific species, but there are several species with westward extensions of their range from Indonesia or Christmas Island, and one south-eastward extension from Sri Lanka (Marsh 1994). The Cocos (Keeling) Islands have a fairly rich fauna of holothurians, including most of the species also known as trepang or beche-de-mer.
Social and Economic Values
The presence of a major bird breeding area, a historic ship wreck, and a near pristine National Park, managed for its wilderness qualities, provides income-generating opportunities for the local Cocos (Keeling) Islands community.
Special interest visitor groups such as bird watchers, eco-tourists, scuba divers and surfers, are attracted to Pulu Keeling National Park. Local licensed tour operators organise specialist trips for particular interest groups. As no camping is permitted on North Keeling Island, visitors have to be accommodated on and transported to and from the southern atoll, thereby providing further opportunities for tourism enterprises and local economic growth.
Parks Australia North operations and staff also contribute to the local economy. Parks Australia hires an ocean-going boat for access to the Park during the trade wind season, and maintenance services are also required for Parks Australia’s work boats, premises and vehicles. Where possible Parks Australia uses local contract personnel and local services for construction, office maintenance and scientific research. At the time of writing this Plan two of the four Parks Australia staff employees are members of the Cocos-Malay community.
Pressures On Pulu Keeling National Park
Pest Species
Yellow crazy ants, Anoplolepis gracilipes, exist on the island but as yet have not developed into supercolonies, probably in part due to the absence of scale insects, (the principal source of the honeydew usually fed on by the ants elsewhere). However, a species of scale has recently been accidentally introduced to the southern atoll.
None of the introduced plant species currently present in Pulu Keeling National Park are considered severe threats (Claussen and Slip 2002), but a number of weeds present on the southern atoll are serious environmental threats. These weeds include Mossman River grass, Cenchrus echinatus, para grass, Brachiaria mutica, buffel grass, Cenchrus ciliaris, Siam weed, Chromolaena odorata, and a photosynthetic bacterium. However, at the time of preparing this Management Plan the paw-paw, Carica papaya, is the most common weed present in the Park, but is not a major threat as it is a non-aggressive species. All visitors and equipment coming into the Park are checked to ensure unwanted species from the southern atoll are not introduced to the Park.
Habitat Loss
Severe tropical cyclones damage vegetation. In April 2001, Cyclone Walter demolished 14% of North Keeling Island’s trees and felled 61% of the canopy. Such weather events have a considerable detrimental effect on the breeding success of seabird populations, but must be considered part of the natural cycle.
Visitor Use
The potential impacts of visitors to the Park include the accidental introduction of pests and diseases, disturbance to nesting birds, littering and habitat degradation (along walking tracks and picnic areas). Due to difficulty of access and requirements that visitors be accompanied by permitted tour operators, visitor numbers to the Park are low and carefully controlled. This assists in preventing further pest species reaching the island, and reduces disturbance to nesting sea birds. Visitors are not permitted to camp on the island. All rubbish is removed from the island.
Other Major Threats
The Cocos-Malay residents of the southern atoll used to hunt considerable numbers of seabirds. Lack of access to the Park for data collection and the introduction of the EPBC Act have resulted in no legal hunting in recent years. Any future hunting will need to be approved under the Act, and will be outside Pulu Keeling National Park. Poaching of seabirds remains an ongoing problem and a significant management issue.
The Cocos-Malay community has relied on seafood since settlement in the 1820’s. Due to difficulties of access, the taking of marine resources from waters around North Keeling Island has always been limited. Fishing in the Park waters has been restricted to trolling by permit only, in order to protect reef species. However, foreign fishermen occasionally illegally fish in the Park and have landed on North Keeling Island and stolen park equipment. The thefts have led to interference with long-term park monitoring programs. Visits by foreign fishermen also have the potential to introduce pests and diseases.
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Figure 1. Location of the Cocos (Keeling) Islands
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Figure 2. The Cocos (Keeling) Islands
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Figure 3. Pulu Keeling National Park and Zoning Plan
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Figure 4. Vegetation and Cross-section of North Keeling Island
Table 1. Cyclones passing over or close to the Cocos (Keeling) Islands
since 1960.
Data are from the Bureau of Meteorology’s cyclone database and other sources. Cyclones listed are those which passed within 100 kilometres of the Islands and had a minimum central pressure of less than 1000 hecto-pascals. Rainfall totals are to the nearest millimetre over a 2 day period. The distances given in the table below are the closest approach of each cyclone to the southern atoll. The minimum central pressure indicates the estimated intensity of the cyclone at the point of closest approach. Maximum wind speed is the maximum gust registered at Cocos Island during the cyclone. (Table adapted from Falkland 1994) and updated.
Name
Date of passing closest to Island
Approx distance away (km)
Min-central pressure when passing closest to Island/min pressure on Island (hecto-pascals)
Max. wind speed on Island (km/hour)
Total rainfall (mm)
Unnamed
13/12/61
60
991/992
122
71
Hazel
9/3/64
80
988/991
102
121
Carol
27/12/65
100
997/1002
95
48
Nancy
14/3/66
100
997/1000
91
26
Doreen
21/1/68
20
970/970
176
219
Dianne
6/1/70
80
996/1005
98
124
Paula
27/3/73
20
999/1006
83
25
Annie
25/11/73
40
995/1002
145
71
Deidre
21/12/73
30
995/994
85
72
Denise
23/5/75
30
995/1002
100
28
Daphne
15/1/82
60
995/998
81
66
Annette
5/2/84
30
994/999
81
142
Daryl
11/3/84
80
984/1001
92
253
Ophelia
12/1/96
30
986/1002
93
252
Alison
8/4/86
30
988/1002
106
112
Fredric
30/1/88
40
988/995
111
90
Herbie
19/5/88
50
990/995
87
57
John
25/1/89
10
997/1000
61
106
Leon
17/2/89
90
990/1006
63
27
Pedro
10/11/89
100
982/1001
137
299
Graham
5/12/91
100
925/1004
98
49
Harriet
27/2/92
10
975/982
163
80
Ken
21/12/92
55
990/1001
111
162
Willy
29/4/94
80
990
102
174
Daryl
17/11/95
140
990
95
156
Hubert
8/1/96
120
995
95
178
Pancho
21/1/97
100
945/1003
96
84
Alison
9/11/98
70
975/999
75
138
Walter
5/4/01
19
940
105
168.8
Dianne
7/4/02
42
986
63
52
Table 2. Flora of Pulu Keeling National Park
Data taken from Gibson-Hill (1948), Australian Biological Resources Study (1993) and Williams (1994a).
Note that this is not a comprehensive list and is mainly extracted from the Ecology Lab Report (1994). It is not specific to the waters of Pulu Keeling National Park but is a general list of fish found in the Cocos (Keeling) Islands (extracted from tables of shallow reefs on the southern atoll; deep coral reefs around North Keeling Island and the southern atoll; and the southern atoll lagoon).
For more comprehensive information on fish species, refer to the Atoll Research Bulletin 399-414 (Woodroffe 1994) .
* Endemic to Christmas and Cocos (Keeling) Islands.
** Undescribed goby of the genus Trimma may have same distibution as Centropyge joculator.