It was a part of Esperance Municipality until 1993 when the municipality was merged with other municipalities to Huon Valley. The island is home to the entire royal penguin population during their annual nesting season. Ecologically, the island is part of the Antipodes Subantarctic Islands tundra ecoregion.
Since 1948 the Australian Antarctic Division has maintained a permanent base, the Macquarie Island Station, on the isthmus at the northern end of the island at the foot of Wireless Hill. The population of the base, the island's only human inhabitants, usually varies from 20 to 40 people over the year. A heliport is located near the base.
In September 2016, the Australian Antarctic Division said it would close its research station on the island in 2017. However, shortly afterwards the Australian government responded to widespread backlash to the decision by announcing funding to upgrade aging infrastructure and continue existing operations at Macquarie Island.
The Australian-Briton Frederick Hasselborough discovered the uninhabited island accidentally on 11 July 1810 when looking for new sealing grounds. He claimed Macquarie Island for Britain and annexed it to the colony of New South Wales in 1810. The island took its name after Colonel Lachlan Macquarie, Governor of New South Wales from 1810 to 1821. Hasselborough reported a wreck "of ancient design", which has given rise to speculation that the island may have been visited before by Polynesians or others.
Fabian Gottlieb von Bellingshausen, who explored the area for Alexander I of Russia, produced the first map of Macquarie Island. Bellingshausen landed on the island on 28 November 1820, defined its geographical position and traded his rum and food for Macquarie Island's fauna with the sealers. Between 1810 and 1919, seals and then penguins were hunted almost to the point of extinction. The conditions on the island and the surrounding seas were considered so harsh that a plan to use it as a penal settlement was rejected.
In 1877, the crew of the schooner Bencleugh was shipwrecked on the islands for four months; folklore says they came to believe there was hidden treasure on the island. The ship's owner, John Sen Inches Thomson, wrote a book on his sea travels, including his time on the island. The book, written in 1912, was entitled Voyages and Wanderings In Far-off Seas and Lands.
In 1890, New South Wales transferred the island to Tasmania, which leased it to Joseph Hatch (1837–1928) between 1902 and 1920 for his oil industry based on harvesting penguins.
Between 1911 and 1914, the island became a base for the Australasian Antarctic Expedition under Sir Douglas Mawson. George Ainsworth operated a meteorological station between 1911 and 1913, followed by Harold Power (1913 to 1914) and by Arthur Tulloch from 1914 until it was shut down in 1915.
In 1933, the authorities declared the island a wildlife sanctuary under the Tasmanian Animals and Birds Protection Act 1928, and in 1972 it was made a State Reserve under the Tasmanian National Parks and Wildlife Act 1970.
The Australian National Antarctic Research Expeditions (ANARE) established its expedition headquarters on 25 May 1948 on Macquarie Island.
The island had status as a biosphere reserve under the Man and the Biosphere Programme from 1977 until its withdrawal from the programme in 2011.
On 5 December 1997, Macquarie Island was inscribed on the UNESCO World Heritage List as a site of major geoconservation significance, being the only place on earth where rocks from the earth's mantle are being actively exposed above sea-level.
On 23 December 2004, an earthquake measuring 8.1 on the moment magnitude scale rocked the island but caused little damage.
Geoscience Australia issued a Tsunami Inundation Advice for Macquarie Island Station. The paper indicates that in certain scenario, a significant tsunami caused by a local earthquake could occur with no warning possible, and could inundate the isthmus where the existing station resides. Such a tsunami would likely affect other parts of the coastline and field huts located close to the shore. Such a significant earthquake at Macquarie Island capable of causing such a tsunami is a high risk according to several papers.
The island is about 34 km (21 mi) long and 5 km (3 mi) wide, with an area of 128 km2 (49 sq mi). Near Macquarie Island are two small groups of minor islands, the Judge and Clerk Islets (54°21′S 159°01′E / 54.350°S 159.017°E / -54.350; 159.017 (Judge and Clerk Islets)), 14 km (9 mi) to the north, 0.2 km2 (49 acres) in area, and the Bishop and Clerk Islets (55°03′S 158°46′E / 55.050°S 158.767°E / -55.050; 158.767 (Bishop and Clerk Islets)), 34 km (21 mi) to the south, 0.6 km2 (150 acres) in area.
The island is in two main pieces of plateau of around 150–200 m (490–660 ft) elevation to the north and south, joined by a narrow isthmus close to sea level. The high points include Mount Elder on the north-east coastal ridge at 385 m (1,263 ft), and Mounts Hamilton and Fletcher in the south at 410 m (1,345 ft).
The Bishop and Clerk Islets are part of the Australian state of Tasmania and mark the southernmost point of Australia (including islands).
In the 19th century a phantom island named "Emerald Island" was believed to lie south of Macquarie Island.
Macquarie Island is an exposed portion of the Macquarie Ridge and is located where the Australian plate meets the Pacific plate. The island lies close to the edge of the submerged microcontinent of Zealandia, but is not regarded as part of it as the Macquarie Ridge is oceanic rather than continental crust.
It is the only place in the Pacific Ocean where rocks from the mantle are actively exposed at sea level. It also is the only oceanic environment with an exposed ophiolite sequence. Due to these unique geological exposures it was made a UNESCO world heritage site in 1997.
Macquarie Island's climate is moderated by the sea, and all months have an average temperature above freezing although snow is common between June and October and may even occur in Macquarie Island's "summer". Its climate is defined as a tundra climate under the Köppen climate classification due to its cool summers.
Average daily maximum temperatures range from 4.9 °C (40.8 °F) in July to 8.8 °C (47.8 °F) in January. Precipitation occurs fairly evenly throughout the year and averages 967.9 mm (38.11 in) annually. Macquarie Island is one of the cloudiest places on Earth with an average of only 856 hours of sunshine per year, similar to that in Tórshavn in the Faroe Islands.
The flora has taxonomic affinities with other subantarctic islands, especially those to the south of New Zealand. Plants rarely grow over 1 m in height, though the tussock-forming grass Poa foliosa can grow up to 2 m tall in sheltered areas. There are over 45 vascular plant species and more than 90 moss species, as well as many liverworts and lichens. Woody plants are absent.
The island has five principal vegetation formations: grassland, herbfield, fen, bog and feldmark. Bog communities include 'featherbed', a deep and spongy peat bog vegetated by grasses and low herbs, with patches of free water. Endemic flora include the cushion plant Azorella macquariensis, the grass Puccinellia macquariensis, as well as two orchids – Nematoceras dienemum and Nematoceras sulcatum.
Mammals found on the island include: subantarctic fur seals, Antarctic fur seals, New Zealand fur seals and southern elephant seals – over 80,000 individuals of this species. Diversities and distributions of cetaceans are less known; southern right whales and orcas are more common followed by other migratory baleen and toothed whales especially sperm and beaked whales prefer deep waters. So called "Upland Seals" once found on Antipodes Islands and Macquarie Island have been claimed as a distinct subspecies of fur seals with thicker furs by scientists although it is unclear whether these seals were genetically distinct.
Royal penguins and Macquarie shags are endemic breeders, while king penguins, southern rockhopper penguins and gentoo penguins also breed here in large numbers. The island has been identified by BirdLife International as an Important Bird Area because it supports about 3.5 million breeding seabirds of 13 species.
The ecology of the island was affected soon after the beginning of European visits to the island in 1810. The island's fur seals, elephant seals and penguins were killed for fur and blubber. Rats and mice that were inadvertently introduced from the ships prospered due to lack of predators. Cats were subsequently introduced deliberately to keep the rodents from eating human food stores. In about 1870, rabbits were left on the island by sealers to breed for food. By the 1970s, the then 130,000 rabbits were causing tremendous damage to vegetation.
The feral cats introduced to the island have had a devastating effect on the native seabird population, with an estimated 60,000 seabird deaths per year. From 1985, efforts were undertaken to remove the cats. In June 2000, the last of the nearly 2,500 cats were culled in an effort to save the seabirds. Seabird populations responded rapidly, but rats and rabbits continued to cause widespread environmental damage.
The rabbits rapidly multiplied before numbers were reduced to about 10,000 in the early 1980s when myxomatosis was introduced. Rabbit numbers then grew again to over 100,000 by 2006. The rodents feed on young chicks while rabbits nibbling on the grass layer has led to soil erosion and cliff collapses, destroying seabird nests. Large portions of the Macquarie Island bluffs are eroding as a result. In September 2006 a large landslip at Lusitania Bay, on the eastern side of the island, partially destroyed an important penguin breeding colony. Tasmania Parks and Wildlife Service attributed the landslip to a combination of heavy spring rains and severe erosion caused by rabbits.
Research by Australian Antarctic Division scientists, published in the 13 January 2009 edition of the British Ecological Society's Journal of Applied Ecology, suggested that the success of the feral cat eradication program has allowed the rabbit population to increase, damaging the Macquarie Island ecosystem by altering significant areas of island vegetation. However, in a comment published in the same journal other scientists argued that a number of factors (primarily a reduction in the use of the Myxoma virus) were almost certainly involved and the absence of cats may have been relatively minor among them. The original authors examined the issue in a later reply and concluded that the effect of the Myxoma virus use was small and reaffirmed their original position.
On 4 June 2007 a media release by the Australian Federal Minister for the Environment and Water Resources, Malcolm Turnbull, announced that the Australian and Tasmanian Governments had reached an agreement to jointly fund the eradication of rodent pests, including rabbits, to protect Macquarie Island's World Heritage values. The plan, estimated to cost $24 million Australian dollars, was based on mass baiting the island similar to an eradication program on New Zealand's Campbell Island, to be followed up with dog hunting teams trained by Steve Austin over a period of up to seven years. The baiting was expected to inadvertently affect kelp gulls, but higher than expected levels of bird deaths caused a temporary suspension of the program. Other species killed by the baits include giant petrels, black ducks and skuas.
In February 2012, The Australian reported that rabbits, rats and mice had been nearly eradicated from the island.
By April 2012, the hunting teams had located and exterminated 13 rabbits still surviving since the baiting in 2011. The last five rabbits found were in November 2011, including a lactating doe and four kittens. No fresh rabbit signs were found up to July 2013. On 8 April 2014 Macquarie Island was officially declared pest-free after seven years of conservation efforts. This achievement is the largest successful island pest-eradication program ever attempted.