Территория Херд и острова Макдональд: Австралийский субантарктический архипелаг

Australian external territory in the sub Antarctic region

The Territory of Heard Island and McDonald Islands (HIMI; ISO 3166 region code: HMD, HM, 334;) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two thirds of the way from Madagascar to Antarctica. The group's overall area is and it has of coastline. Discovered in the mid 19th century, the islands lie on the Kerguelen Plateau in the Indian Ocean and have been an Australian territory since 1947. They contain Australia's only two active volcanoes. The summit of one, Mawson Peak, is higher than any mountain in all other Australian states or territories, except Dome Argus, Mount McClintock and Mount Menzies in the Australian Antarctic Territory. The islands are among the most remote places on Earth: They are located about southwest of Perth, southwest of Cape Leeuwin, Australia, southeast of South Africa, southeast of Madagascar, north of Antarctica, and southeast of the Kerguelen Islands (part of French Southern and Antarctic Lands). The islands, which are uninhabited, can be reached only by sea, which from Australia takes two weeks in the vessels normally used to access them.

Neither island cluster had recorded visitors until the mid 1850s. An American sailor, John Heard, on the ship Oriental, sighted Heard Island on 25 November 1853, en route from Boston to Melbourne. He reported the discovery one month later and had the island named after him. William McDonald aboard the Samarang discovered the nearby McDonald Islands six weeks later, on 4 January 1854. No landing took place on the islands until March 1855, when sealers from the Corinthian, led by Erasmus Darwin Rogers, went ashore at a place called Oil Barrel Point. From 1855 to 1882 a number of American sealers spent a year or more on the island, living in appalling conditions in dark smelly huts, also at Oil Barrel Point. At its peak the community consisted of 200 people. By 1880, sealers had wiped out most of the seal population and then left the island. In all, the islands furnished more than 100,000 barrels of elephant seal oil during this period. A number of wrecks have occurred in the vicinity of the islands. There is also a discarded building left from John Heard's sealing station that is situated near Atlas Cove. The islands were formally claimed by the United Kingdom in 1910 and transferred to Australia on 26 December 1947. The transfer was confirmed in letters exchanged on 19 December 1950. There were at least five private expeditions to Heard Island between 1965 and 2000. Several amateur radio operators have visited Heard, often associated with scientific expeditions. The first activity there was in 1947 by Alan Campbell Drury. Two amateur radio DXpeditions to the island took place in 1983 using the callsigns VK0HI (the Anaconda expedition) and VK0JS and VK0NL (the Cheynes II expedition), with a further operation in January 1997 (VK0IR). The DXpedition in March 2016 (VK0EK) was organised by Cordell Expeditions, and made over 75,000 radio contacts. Mawson Peak, atop Big Ben, was first climbed on 25 January 1965 by five members of the Southern Indian Ocean Expedition to Heard Island (sometimes referred to as the Patanela expedition). The second ascent was made by five members of the Heard Island Expedition 1983 (sometimes referred to as the Anaconda expedition). The US Navy vessels and were used to transmit signals which could be detected as far away as both ocean coasts of the US and Canada.

The islands are part of the Southern Indian Ocean Islands tundra ecoregion that includes several subantarctic islands. In this cold climate, plant life is mainly limited to grasses, lichens, and mosses. Low plant diversity reflects the islands' isolation, small size, severe climate, the short, cool growing season and, for Heard Island, substantial permanent ice cover. The main environmental determinants of vegetation on subantarctic islands are wind exposure, water availability, parent soil composition, salt spray exposure, nutrient availability, disturbance by trampling (from seabirds and seals) and, possibly, altitude. At Heard Island, exposure to salt spray and the presence of breeding and moulting seabirds and seals is a particularly strong influence on vegetation composition and structure in coastal areas.

Evidence from microfossil records indicates that ferns and woody plants were present on Heard Island during the Tertiary (a period with a cool and moist climate). Neither group of plants is present today, although potential Tertiary survivors include the vascular plant Pringlea antiscorbutica and six moss species. Volcanic activity has altered the distribution and abundance of the vegetation. The vascular flora covers a range of environments and, although only six species are currently widespread, glacial retreat and the consequent connection of previously separate ice free areas is providing opportunities for further distribution of vegetation into adjacent areas.

Low growing herbaceous flowering plants and bryophytes are the major vegetation components. The vascular flora comprises the smallest number of species of any major subantarctic island group, reflecting its isolation, small ice free area and severe climate. Twelve vascular species are known from Heard Island, of which five have also been recorded on McDonald Island. None of the vascular species are endemic, although Pringlea antiscorbutica, Colobanthus kerguelensis, and Poa kerguelensis occur only on subantarctic islands in the southern Indian Ocean. The plants are typically subantarctic, but with a higher abundance of the cushion forming Azorella selago than other subantarctic islands. Heard Island is the largest subantarctic island with no confirmed human introduced plants. Areas available for plant colonisation on Heard Island are generally the result of retreating glaciers or new ice free land created by lava flows. Today, substantial vegetation covers over 20 km2 of Heard Island, and is best developed on coastal areas at elevations below 250 m.

Bryophytes (mosses and liverworts) contribute substantially to the overall biodiversity of Heard Island, with 43 mosses and 19 liverworts being recorded, often occupying habitats unsuitable for vascular plants, such as cliff faces. Bryophytes are present in most of the major vegetation communities including several soil and moss inhabiting species. A 1980 survey of McDonald Island found lower diversity than that on Heard Island; four mosses and a number of algal species are recorded from there.

At least 100 species of terrestrial algae are known from Heard Island, commonly in permanently moist and ephemeral habitats. Forests of the giant Antarctic kelp Durvillaea antarctica occur at a number of sites around Heard Island and at least 17 other species of seaweed are known, with more to be added following the identification of recent collections. Low seaweed diversity is due to the island's isolation from other land masses, unsuitable beach habitat, constant abrasion by waves, tides and small stones, and the extension of glaciers into the sea in many areas.

Heard Island has a range of terrestrial environments in which vegetation occurs. Seven general vegetation communities are currently recognised, although vegetation composition is considered more of a continuum than discrete units:
Subantarctic vegetation is minimal and includes small types of shrubbery, including mosses and liverworts. Open cushionfield vegetation is the most widespread and abundant vegetation type on Heard Island. It is characterised by Azorella selago cushions interspersed with bryophytes, small vascular species and bare ground with 20–75% cover, and found mainly at altitudes between 30 and 70 m asl. Fellfield describes vegetation with abundant bare ground and less than 50% plant cover. Fellfield may occur as a result of harsh climatic or edaphic factors, or recent deglaciation which has exposed bare ground. Mossy fellfield is a community with high species richness and consists of bryophytes and small Azorella selago cushions. It is found at altitudes between 30 and 150 m in areas with intermediate exposure. Wet mixed herbfield occurs on moist substrate, mostly on moraines and moist lee slopes (often in association with burrowing petrels colonies) at low altitude (< 40 m) where the water table is at or close to the surface. Species richness is highest here of all the communities, with dominant species being Poa cookii, Azorella selago, Pringlea antiscorbutica, Acaena magellanica, and Deschampsia antarctica. Coastal biotic vegetation is dominated by Poa cookii and Azorella selago, occurring mainly on coastal sites of moderate exposure and in areas subject to significant influence from seals and seabirds. Saltspray vegetation is dominated by the salt tolerant moss Muelleriella crassifolia and limited in extent, being found at low elevations on lavas in exposed coastal sites. Closed cushionfield is found on moraines and sand at altitudes mostly below 60 m, and is dominated almost entirely by Azorella selago cushions that often grow together to form continuous carpets which can be subject to burrowing by seabirds.

One of the most rapidly changing physical settings in the subantarctic has been produced on Heard Island by a combination of rapid glacial recession and climate warming. The consequent increase in habitat available for plant colonisation, plus the coalescing of previously discrete ice free areas, has led to marked changes in the vegetation of Heard Island in the last 20 years or so. Other species and vegetation communities found on subantarctic islands north of the Antarctic Convergence now absent from the Heard Island flora may colonise the island if climate change produces more favourable conditions. Some plant species are spreading and modifying the structure and composition of communities, some of which are also increasing in distribution. It is likely that further changes will occur, and possibly at an accelerated rate. Changes in population numbers of seal and seabird species are also expected to affect the vegetation by changing nutrient availability and disturbance through trampling. One plant species on Heard Island, Poa annua, a cosmopolitan grass native to Europe, was possibly introduced by humans, though is more likely to have arrived naturally, probably by skuas from the Kerguelen Islands where it is widespread. It was initially recorded in 1987 in two deglaciated areas of Heard Island not previously exposed to human visitors, while being absent from known sites of past human habitation. Since 1987 Poa annua populations have increased in density and abundance within the original areas and have expanded beyond them. Expeditioner boot traffic during the Australian Antarctic program expedition in 1987 may be at least partly responsible for the spread, but it is probably mainly due to dispersal by wind and the movement of seabirds and seals around the island. The potential for introducing plant species (including invasive species not previously found on subantarctic islands) by both natural and human induced means is high. This is due to the combination of low species diversity and climatic amelioration. During the 2003/04 summer a new plant species, Cotula plumosa, was recorded. Only one small specimen was found growing on a coastal river terrace that had experienced substantial development and expansion of vegetation over the past decade. The species has a circumantarctic distribution and occurs on many subantarctic islands.

71 species of lichens have been recorded from Heard Island and they are common on exposed rock, dominating the vegetation in some areas. As with plants, a 1980 survey of McDonald Island found lower diversity there, with just eight lichen species and a number of non lichenized fungi recorded.

The main indigenous animals are insects along with large populations of ocean going seabirds, seals and penguins.

Sealing at Heard Island lasted from 1855 to 1910, during which time 67 sealing vessels are recorded visiting, nine of which were wrecked off the coast. Relics that survive from that time include trypots, casks, hut ruins, graves and inscriptions. This caused the seal populations there to either become locally extinct or reduced to levels too low to exploit economically. Modern sealers visited from Cape Town in the 1920s. Since then the populations have generally increased and are protected. Seals breeding on Heard include the southern elephant seal, the Antarctic fur seal and the subantarctic fur seal. Leopard seals visit regularly in winter to haul out though they do not breed on the islands. Crabeater, Ross and Weddell seals are occasional visitors.

Heard Island and the McDonald Islands are free from introduced predators and provide crucial breeding habitat in the middle of the vast Southern Ocean for a range of birds. The surrounding waters are important feeding areas for birds and some scavenging species also derive sustenance from their cohabitants on the islands. The islands have been identified by BirdLife International as an Important Bird Area because they support very large numbers of nesting seabirds. Nineteen species of birds have been recorded as breeding on Heard Island and the McDonald Islands, although recent volcanic activity at the McDonald Islands in the last decade is likely to have reduced vegetated and un vegetated nesting areas. Penguins are by far the most abundant birds on the islands, with four breeding species present, comprising king, gentoo, macaroni and eastern rockhopper penguins. The penguins mostly colonise the coastal tussock and grasslands of Heard Island, and have previously been recorded as occupying the flats and gullies on McDonald Island. Other seabirds recorded as breeding at Heard Island include three species of albatross (wandering, black browed and light mantled albatrosses), southern giant petrels, Cape petrels, four species of burrowing petrels (Antarctic and Fulmar prions, common and South Georgia diving petrels), Wilson's storm petrels, kelp gulls, subantarctic skuas, Antarctic terns and the Heard shag. although a Convention for the Conservation of Antarctic Marine Living Resources CCAMLR) Working Group was cautious about the interpretation of the increasing trend given the disparate nature of the data, as discussed in the paper. The discovery of a large, previously unknown, colony of Heard shags in 2000/01 at Cape Pillar raised the known breeding population from 200 pairs to over 1000 pairs. Due to the steep topography of Heard Island, most of its glaciers are relatively thin (averaging only about in depth). The presence of glaciers on Heard Island provides an excellent opportunity to measure the rate of glacial retreat as an indicator of climate change. Available records show no apparent change in glacier mass balance between 1874 and 1929. Between 1949 and 1954, marked changes were observed to have occurred in the ice formations above 5000 feet on the southwestern slopes of Big Ben, possibly as a result of volcanic activity. By 1963, major recession was obvious below 2000 feet on almost all glaciers, and minor recession was evident as high as 5000 feet. The coastal ice cliffs of Brown and Stephenson Glaciers, which in 1954 were over 50 feet high, had disappeared by 1963 when the glaciers terminated as much as 100 yards inland. Retreat of Heard Island glaciers is most dramatic on the eastern section of the island, where the termini of former tidewater glaciers are now located inland. Based on the findings of that expedition, the rate of loss of glacier ice on Heard Island appears to be accelerating. Between 2000 and 2003, repeat GPS surface surveys revealed that the rate of loss of ice in both the ablation zone and the accumulation zone of Brown Glacier was more than double average rate measured from 1947 to 2003. The increase in the rate of ice loss suggests that the glaciers of Heard Island are reacting to ongoing climate change, rather than approaching dynamic equilibrium. The islands are a territory (Territory of Heard Island and McDonald Islands) of Australia administered from Hobart by the Australian Antarctic Division of the Australian Department of Climate Change, Energy, the Environment and Water. The administration of the territory is established in the Heard Island and McDonald Islands Act 1953, which places it under the jurisdiction of the Supreme Court of the Australian Capital Territory, with the non criminal laws of the Australian Capital Territory and the criminal laws of Jervis Bay Territory applying to the Territory. The islands are contained within a marine reserve and are primarily visited for research, meaning that there is no permanent human habitation. In part to carry out this mission, as of 2023, the Navy's Armidale class boats are in the process of being replaced by larger s.

Despite the lack of population, the islands have been assigned the country code HM in ISO 3166 1 (ISO 3166 2:HM) and therefore the Internet top level domain hm. The time zone of the islands is UTC+5.