Macquarie Island provides evidence of the rock types found at great depths in the earth’s crust and of plate tectonics and continental drift; the geological processes that have dominated the earth’s surface for many millions of years. It is the only island in the world composed entirely of oceanic crust and rocks from the mantle, deep below the earth’s surface. Macquarie Island probably began as a spreading ridge under the sea with the formation of new oceanic crust somewhere between 11 and 30 million years ago. At some stage the spreading halted and the crust began to compress, squeezing rocks from deep within the mantle upward like toothpaste from a tube. As the ridge grew it eventually became exposed above the ocean’s surface about 600,000 years ago. Thus, rocks normally only occurring deep within the earth’s mantle have become exposed on the earth’s surface. Since Macquarie Island emerged, it has mainly been carved by marine processes such as wave action, unlike other subantarctic islands, which have been shaped by glaciers. The geodiversity of Macquarie Island provides the foundation for the landforms, soils, plants and animals occurring there. It is an island of unique natural diversity, a site of major geoconservation significance and one of the truly remarkable places on earth. Around the shoreline there is a coastal terrace formed from a wave-cut platform now raised above sea level. Vast waterlogged areas on the coastal platform are heavily vegetated, forming a mire based on deep peat beds and known locally as “featherbed” from the sensation gained when walking over them. Old sea stacks testify to the continual uplifting of the island as they protrude through the peat beds, some of them now being several hundred metres from the existing coastline. Behind the coastal terrace, steep escarpments rise more than 200 metres to the undulating central plateau which has three peaks over 400 metres; the highest being Mt Hamilton at 433 metres. The slopes from the plateau to the sea are most spectacular at the southern end of the island and along the west coast where the relentless pounding of the Southern Ocean has cut a myriad of rugged bays and coves, fringed with sea stacks and reefs. The plateau surface is dotted with innumerable lakes, tarns and pools, mainly of structural origin. Fluctuations in sea level and marine erosion have cut away the original escarpments leaving some lakes perched on the edge of the plateau, while others have been partially or totally drained. The continual westerly winds, which increase in force as they rise over the barrier of the island, and changes in the topography on the plateau, result in dramatic changes in the vegetation cover. Among the most aesthetically appealing sights of the island are the vast congregations of wildlife, particularly penguins during breeding seasons. The breeding population of royal penguins on Macquarie Island is estimated at over 850,000 pairs – one of the greatest concentrations of sea birds in the world. Four species of albatross nest on steep and rugged cliffs, both on the main island and on nearby Bishop and Clerk Islands. These are majestic birds, easily viewed when nesting. Elephant seals also form impressive colonies on suitable beaches during the breeding season. These animals can grow to over 4.5 metres in length and to a weight of 3.5 tonnes. Conflicts between the larger bulls are among the more memorable sights that may be witnessed on the island. Macquarie Island and the Bishop and Clerk Islets, about 37 kilometres to the south, and Judge and Clerk Islets about 11 kilometres to the north, form a Nature Reserve with protection extending out to three nautical miles from the coast. Some of the marine values beyond state waters are also protected by the Macquarie Island Marine Park declared by the Australian Government on 28 October 1999. The primary purpose of the marine park is to protect the conservation values of the region from human disturbance. The marine park contains one of the world’s largest highly protected marine zones, covering more than 160,000 km². There are no permanent human inhabitants on Macquarie Island although the Australian Antarctic Division station is occupied year round. The only access to the island is by sea.
Macquarie Island
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Government evidence of impact of climate change:
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IUCN World Heritage Outlook, Macquarie Island, 2014
Current state and trend of VALUES Low Concern Trend Data Deficient The geological values for which the site was inscribed are unchanged; while the landscape values have undergone some deterioration; mainly due to the devastation caused by invasive species and possibly exacerbated by climate change.
Potential Threats High Threat Climate change has already been shown to be having effects as the island gets warmer and drier and rainfall patterns change; and populations of Rockhopper Penguins for example have crashed elsewhere as their food source (krill) moves south.
Global conservation status for King Penguins (Aptenodytes patagonicus) is Least Concern; Gentoo (Pygoscelis papua ) Near Threatened and Rockhopper (Eudyptes chrysocome) VU (Birdlife; 2012).
Although atmospheric drying is occurring; rainfall patterns are changing and precipitation is increasing (Adams 2009) leading to an increase in soil moisture which appears to be exacerbating erosion and slope instability (Scott and Kirkpatrick 2013).
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IUCN World Heritage Outlook, Macquarie Island, 2017
Possible cause has been potential link between climate change and a pathogen (Whinam et al.; 2014).
Ocean acidification; Temperature extremes High Threat Inside site; throughout( 50 ) Outside site Climate change has already been shown to be having effects as the island gets warmer and drier and rainfall patterns change.
Potential Threats High Threat Climate change has already been shown to be having effects as the island gets warmer and rainfall patterns change.
Dramatic changes in vegetation cover due to climatic conditions Low Concern Trend Data Deficient The as yet undetermined die off of the Macquarie cushion plants (Whinam et al.; 2014a) is of concern.
No population decline has been signalled on Macquarie; although the global conservation status of the Royal Penguin is Near Threatened (Birdlife International; 2017) and the species is endemic to the property.
A number of measures have been implemented to identify the cause of the dieback (SOC; 2010) but one potential cause is a pathogen; exacerbated by climate change (Whinam et al.; 2014a).
Although atmospheric drying is occurring; rainfall patterns are changing and precipitation is increasing (Adams 2009) leading to an increase in soil moisture which appears to be exacerbating erosion and slope instability (Scott and Kirkpatrick 2013; Whinam et al.; 2014b).
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IUCN World Heritage Outlook, Macquarie Island, 2020
Criterion (vii) Dramatic changes in vegetation cover due to climatic conditions Changes in topography result in dramatic changes in the vegetation cover which can vary from lush grassland to sparse feldmark within the space of a few metres (World Heritage Committee; 2012).
Climate change is now recognised as a primary causative factor in the die back of A. macquariensis; and may be having as of yet unquantified impacts on other factors which contribute to the values of the site.
The cause of the dieback has been attributed to climate change related changes in soil conditions interacting with the cushions and a likely; although as yet unidentified; pathogen (Whinam et al.; 2014 Dickson et al.; 2019).
Although not yet fully understood; environmental changes brought about by a changing climate are widely considered to be the primary factor responsible for the dieback (IUCN Consultation; 2017 Bergstrom et al. 2015).
Ocean acidification; Temperature extremes (Climate change) High Threat Inside site; throughout( 50 ) Outside site Climate change has been shown to be having effects on several levels.
Changing climate is considered to be a causative factor in the dieback of the endemic cushion plant Azorella macquariensis and could increase risk from invasive plant species by improving growing conditions (Bergstrom et al.; 2015 IUCN Consultation; 2017).
Potential Threats High Threat Climate change has already been shown to be having effects as the island gets warmer and rainfall patterns change.
However; climate change is currently threatening some values of the site; which may increase in the future as changes in climate become more acute.
Dramatic changes in vegetation cover due to climatic conditions Low Concern Trend Data Deficient The dieback of the Macquarie cushion plants (Whinam et al.; 2014a Dickson et al.; 2019) is of great concern.
The root cause has now been attributed to climate change interacting with a pathogen (Whinam et al.; 2014a Dickson et al. 2019).
Factors negatively affecting provision of this benefit Climate change Impact level High; Trend Increasing Pollution Impact level Low; Trend Increasing Invasive species Impact level Low; Trend Continuing Importance for research Much scientific research has been carried out on the island and will continue into the longer term.
Although atmospheric drying is occurring; rainfall patterns are changing and precipitation is increasing (Adams 2009) leading to an increase in soil moisture which appears to be exacerbating erosion and slope instability (Scott and Kirkpatrick 2013; Whinam et al.; 2014b).
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Parks and Wildlife Service Tasmania, Macquarie Island Nature Reserve and World Heritage Area Management Plan 2006
Warmer temperatures resulting from global climate change are likely to increase the risk and impact of introductions due to more favourable survival conditions.
However; in the last few years rabbits appear to have greatly increased in localised areas due to a combination of factors cat eradication; climate change and possible attenuation of myxoma virus effectiveness.
Brothers (pers. comm.) does not agree that rats will necessarily reduce nest site availability for smaller seabirds; but believes that effects of climate change and rabbit control may be greater determinants.
Modification of vegetation will occur with global climate change.
The combined effect of the eradication of cats; warm weather and dry conditions has resulted in a substantial and rapid increase in the rabbit population.
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UNESCO, World Heritage Committee Thirty-seventh session: Item &B of the Provisional Agenda: State of conservation of World Heritage properties inscribed on the World Heritage List, WHC-13/37.COM/7B
Initiatives were also undertaken to share the innovative climate change adaptation measures with other countries where coral reef systems suffer from the effects of climate change.
In addition; climate change effects; including increasing cyclone activity; as well as increasing water levels and salinity in Lake Tegano; induced by sea level rise; have led to shortages of housing; food and medical supplies.
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