Biogeography

Maudlandia Antarctic desert

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Ice Balls near Auster Rookery 1992 Australian Antarctic Division photo by K.Sheridan © Commonwealth of Australia

Antarctica remains the only relatively unspoiled continent on our planet. Almost entirely covered in a permanent ice cap that reaches as much as 4776 meters in thickness, conditions for life are quite extreme—but, not impossible. Terrestrial vegetation is limited in Maudlandia, though the Dry Valleys region of continental Antarctica is a fascinating ecosystem of flora and fauna highly adapted to polar desert conditions. Colonies of seabirds, penguins, and seals abound around the coasts, obtaining their sustenance from the highly-productive Antarctic seas. While this continent has had relatively little direct interference from humans, it is activity elsewhere that may have the greatest effect on Antarctica. Production of certain gases has contributed to a serious depletion of ozone in the atmosphere over Antarctica, as well as contributing to global warming, which could potentially lead to the melting of vast quantities of ice.

Location and General Description


 

Antarctica is the coldest, driest, windiest, on average highest, and most isolated continent on the planet. It covers almost 10 percent of the land surface on Earth, at 13.9 million km2. However, 98% of this area is covered by a permanent sheet of ice, that contains 90% of the world’s ice and almost 70% of the Earth’s fresh water. The remaining 2% of land area, restricted primarily to the coastal fringes of the continent, is where the majority of Antarctica’s limited terrestrial life exists. Ice-free Antarctica can be roughly divided into two biogeographic regions: the Antarctic Peninsula, here termed Marielandia, and the continental coast, or Maudlandia. The Transantarctic Mountains extend 3,200 km dividing the continent into East (Maudlandia) and West (Marielandia). The average elevation of the range is 2300 meters (m), with highs reaching 4.270 m, similar to the U.S. Rockies. Some volcanic activity occurs along the Transantarctic Mountains, for example, Mount Erebus (77.5°S) at the edge of McMurdo Sound, is the world’s southernmost active volcano.

Maudlandia covers a greater area than Marielandia, about two-thirds of the continent. However, the whole of this region is subject to a harsh continental Antarctic climate, which is cold, windy and arid. Mean monthly temperatures only exceed 0°C for a month or less during the summer, and winter averages range from –5 to -25°C. The ice-free portions of the region are characterized by semi-desert with moss and algae vegetation on ahumic soil. While the flora is restricted in species and extent, there are many lichens present that are capable of forming local, extensive stands. Snow algal growth can be found in some places. Rain is quite rare, with an annual precipitation just above 10-15 cm. Invertebrates can be locally abundant. Farther inland from the coast, in the mountain and glacier zone that encircles the central ice sheet, the climate becomes colder and drier. All monthly average temperatures are below -5°C, there is no rainfall, and precipitation is only the water equivalent of 10 cm annually. This area is considered Antarctic Desert, and is concentrated within three parallel valleys, Victoria, Wright, and Taylor, near the McMurdo Sound. The unique Dry Valley ecosystem covers about 1500 sq of ground kept bare by strong winds that blast snow and precipitation away, preventing the build-up of ice. Several large lakes occur in the valleys, some of which are frozen solid, though a few are not. For example, one lake maintains 43°C water below its 3 m thick ice ceiling, because the salinity of the water traps enough heat to keep it liquid. One 18 mile river flows with glacier melt during one to two months of summer. Generally, the limited vegetation consists of open, discontinuous lichen growth, with occasional patches of moss near scarce snow patches, bird colonies, or other favorable spots. A depauperate assemblage of mites, springtails, and other invertebrates are present.

Biodiversity Features

Maudlandia differs from Marielandia in that the larger expanses of ice-free land are found inland, rather than near the coast. It is within the McMurdo Dry Valleys that the most outstanding examples of life adapted to the extreme climate occur. In this landscape that was once assumed to be completely barren, microbiologists in the 1970s discovered communities of microscopic algae, fungi, and bacteria living protected inside rocks. These organisms live in minute gaps between grains of sandstone, close to the surface of the semi-translucent rock where they can receive some sunlight and moisture, and also receive nourishment from the minerals in the stone. These organisms are known as cryptoendolithic microorganisms. Other such algal species as Hemichloris antarctica, are specially adapted to repeated freezing and re-thawing. Recently discovered by divers, the bottom of some lakes support a microbial mat made up of many species of blue-green algae, similar to those thought to be the earliest life-forms and the original sources of oxygen on the planet. The unlikely top predator within the Dry Valleys is a bacteria-eating nematode that can survive multiple years of being freeze-dried—entering a state called anhydrobiosis. Certain lichen species, for example, Buellia frigida, might grow as little as 1 cm in 1000 years. The area's harsh conditions and the organisms that have adapted to them are often considered to be an approximation of life that may exist on Mars. 

caption Emperor penguins (Aptenodytes forsteri) in the Southwest Ross Sea. (Photograph by Michael Van Woert, NOAA Photo Library)

Certain areas within Maudlandia have been designated as Specially Protected Areas due to their unique flora. Barwick Valley (approximately 77°S, 161°E) has one of the least disturbed or contaminated of the Dry Valleys of Victoria Land. Cryptogram Ridge on Mount Melbourne, Victoria Land (74°21'S, 164°42'E) has geothermal activity that supports a unique community of bryophytes, algae, and microbiota (including the only known occurrence in the Antarctic of the moss, Campylopus pyriformis) and the very rare continental occurrence of the liverwort, Cephaloziella exiliflora. This site can only be compared with one other known high-altitude geothermally-influenced ice-free area near the summit of Mount Erebus.

As all larger animals of the terrestrial ecosystem of Antarctica obtain their food from the productive waters of the Southern Ocean, it is the coastal areas of Maudlandia that are populated with large colonies of birds and seals. The characteristic animal of Antarctica, the flightless penguin, can exist in the southern polar regions only due to a lack of any significant predators. In the Arctic, penguins would be far too vulnerable to such carnivores as polar bear and Arctic fox. Leopard seals are important penguin predators. Of the estimated total of 350 million birds of all species in the Antarctic, about 175 million are penguins, and the rest are flying birds. Six species of penguin are considered native to the Antarctic region: Adélie penguin (Pygoscelis adeliae), chinstrap penguin (P. antarctica), gentoo penguin (P. papua), emperor penguin (Aptenodytes forsteri), king penguin (A. patagonicus), rockhopper penguin (Eudyptes crestatus), and macaroni penguin (E. chrysolophus). Four of these breed on the continent: the Adélie, emperor, chinstrap, and gentoo penguins. Adélie penguins are by far the most plentiful penguin species on the continent.

The emperor penguin is the largest (100-130 cm tall, 30 to 33 kg) and perhaps most unusual penguin of the group. Of all the penguin species, only the emperor breeds during the cold, dark winter months in Antarctica. Breeding colonies are generally found on sea-ice far from the open ocean where temperatures are as low as -60° C and winds can reach 180 km per hour. Females lay a single egg in May after a 63-day gestation period, and then pass the egg over to their mate, leaving to feed at sea. During incubation, the male penguin fasts for 9 weeks, and may lose as much as one-third of his body weight. Males huddle together for warmth and protection, each balancing an egg on his feet, where it is insulated by a thick roll of skin and feathers. When the female returns, she takes over feeding the hatchling for a period of six weeks, while the male takes his turn making the long journeys over the ice (up to 100 km) in search of food. When the young are about seven weeks old, they join other chicks in a crèche, which is protected by a few adults. By January the sea-ice begins to break out, and chicks have begun to shed their soft down allowing them to fend for themselves. A possible explanation for the emperor penguin’s winter breeding behavior is that it developed to allow the chick to grow to independence at a time when food is most plentiful. This pattern leads to one concern associated with global warming. Were sea-ice to break early, entire generations of emperor penguin could be lost if the incubation of eggs were disturbed or if chicks were exposed to sea spray before shedding their vulnerable down.

Thirty-seven flying seabird species are native to Antarctica. Species breeding in Maudlandia include southern fulmar (Fulmaras glacialoides), southern giant fulmar (Macronectes giganteus), cape pigeon (Daption capense), snow petrel (Pagodroma nivea), Wilson’s storm petrel (Oceanites oceanicus), south polar skua (Catharacta maccormicki), and Antarctic petrel (Thalassoica antarctica). Several areas have been given specially protected status due to large colonies of breeding birds. Taylor Rookery, in Mac Robertson Land (67°26'S, 60°50'E) contains a colony of emperor penguins which is one of the few, and probably the largest, of the known colonies of this species breeding entirely on land. Other important breeding sites on the continent are the Rookery Islands, Holme Bay; Ardery Island and Odbert Island, Budd Coast; Cape Crozier; and Cape Hallett, Victoria Land.

Six seal species are native to Antarctica: Crabeater Seal (Lobodon carcinophagus), Ross Seal (Omimatophoca rossii), Leopard Seal (Hydrurga leptonyx), Weddell Seal (Leptonychotes weddellii'), Southern Elephant Seal (Mirounga leonina), and southern fur seal (Arctocephalus gazella). The elephant seal and fur seal are more often associated with the open ocean, while the others spend a significant amount of time on sea ice. Seals hauling out on land can have a significant impact on vegetation communities. While seals primarily feed on krill, squid, and other marine species, some, such as the leopard seal, will occasionally eat small penguins.

Terrestrial invertebrates of Antarctica are limited to arthropods, primarily being springtails, mites, and midges that are associated with plant communities along the coasts. One mite, Nanorchestes antarcticus, which has the widest distribution of any Antarctic arthropod, was also reported as the southernmost occurring animal when it was located at 85°32’ S, 153°W, about 500 km from the South Pole.

Current Status

The Antarctic Treaty was signed in 1959 and now holds signatures of 44 nations. The treaty applies to the area south of 60° south latitude, including all islands and ice shelves. It includes prohibitions on the killing, wounding, capturing or molesting of any native mammal or native bird—except in accordance with a permit—as well as regulations on the importation of exotic species, parasites, and diseases. Permits may only be issued by persons authorized by a participating government. Also, numerous conservation areas are designated in several categories, and carry further regulations. For example, vehicles are prohibited to enter Specially Protected Areas.

The Antarctic Treaty has, for the time being, put a ban on any Antarctic nuclear testing, radioactive waste disposal, and oil or other mineral drilling. It does not, however, prevent environmental degradation altogether. Much of the Antarctic ecosystem, particularly its flora, is extremely vulnerable to even the slightest disturbance. Several thousand researchers and tourists visit the continent each year. While the majority of tourism is concentrated at the more accessible Antarctic Peninsula, it is a growing industry on the continental portion, corresponding with the rising interest in adventure tours. Ship-based tours visit McMurdo Sound in the Ross Sea, viewing historic huts and scientific research stations. Helicopter tours to the Dry Valleys are part of one tour-operator’s itinerary. A few studies have been done on the impact of human disturbance in Antarctica. It was found that the nesting pairs of Adélie penguins in a rookery close to McMurdo Station dropped by half after the station was established and disturbance by humans and helicopters began. The rookery has partially recuperated since more protective measures were put in place.

Types and Severity of Human Impact

As the last relatively unspoiled continent on the planet, conservation in Antarctica is far more organized and effective than anywhere else on Earth. Potential future threats to the Antarctic environment would likely result from activities undertaken far from the isolated wilderness. The dramatic loss of ozone in the atmosphere over Antarctica was first noticed by the British Antarctic Survey over Halley Station in Queen Maud Land in 1984. It is believed to be the result of widespread use of CFC’s (chlorofluorocarbons) as cooling agents. This possibility had been raised in the 1970’s, and restrictions had been put on the use of CFC’s. However, their persistence in the atmosphere, combined with the unique circulation in the stratosphere that is centered over the stable Antarctic vortex, led to this unexpected, massive depletion of ozone. A smaller hole was found in the Arctic, though its vortex is less stable, producing conditions less likely to create an ozone hole.

Though UV-B radiation accounts for less than 1% of the Earth’s total sunlight, it has the ability to damage organisms by disrupting basic biological processes. It is also a well-known contributor to the development of skin cancer. The study of lichens in Antarctica, which are adapted to high levels of UV-B radiation, may lead to beneficial discoveries. Certain species of lichens (e.g. Usnea aurantiaco-atra) produce higher levels of usnic acid when levels of UV-B are higher. Usnic acid levels in old lichen specimens from herbariums show lower levels of usnic acid than recent specimens from the same place, indicating that UV-B levels were lower in recent history.

Global warming, as a result of human production of greenhouse gases, threatens to melt large amounts of the ice that makes up most of the Antarctic. Were this to take place rapidly, flora and fauna highly adapted to the particular conditions of polar regions could be drastically disrupted, for example in the case mentioned earlier with the emperor penguin. The continent of Antarctica cannot be considered as entirely separate from the populated portions of the Earth. The polar region play a key role in worldwide weather patterns. To an extent, the polar seas act as ‘heat sinks’, partially counteracting the greenhouse effect from build-up of carbon dioxide in the atmosphere. Changes in climate in Antarctica would certainly carry tangible effects to the populated continents of the planet.

Justification of Ecoregion Delineation

Udvardy differentiates two Antarctic provinces within the Antarctic continent. The East Antarctic Province, or Maudlandia, from Queen Maud Coast in the northwest sector, encompasses the majority of mainland Antarctica, excluding the Antarctic Peninsula. The ecoregion boundary corresponds to coastal fringes of the continent that are free of permanent ice.

Additional information on this ecoregion

Further Reading

See Also

Disclaimer: This article contains information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

 

Glossary

Citation

Fund, W. (2014). Maudlandia Antarctic desert. Retrieved from http://www.eoearth.org/view/article/51cbee6a7896bb431f697adb

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