Description
Location and General Description
This ecoregion is delineated as the coastal fringes of the Antarctic peninsula, which are free of permanent ice. Stretching north towards the southern tip of South America, this area is the portion of Antarctica closest to another continent. Ninety-eight percent of Antarctica’s 14.3 million km2 is covered by a permanent sheet of ice, which contains 90% of the world’s ice and almost 70% of the Earth’s fresh water. During winter months, the extent of sea ice increases five-fold, dramatically pushing the border of open ocean away from the land (EPA 2001). The coast can be roughly divided into two biogeographic regions: the Antarctic Peninsula, here termed Marielandia, and the continental coast, or Maudlandia. While Maudlandia covers a greater area than Marielandia, the climate of the peninsula, especially on the western coast, is the mildest on the continent. The west coast of the Antarctic Penensula has a maritime Antarctic climate, similar to that of the South Sandwich, South Orkney, and South Shetland offshore islands. From the tip of the Antarctic peninsula south to 68°S, average monthly temperatures exceed 0°C for 3-4 months of summer, and rarely fall below -10°C during winter (EPA 2001). Precipitation averages 35-50 cm per year with a good portion falling as rain during summer, occurring on two-thirds of the days of the year, with little seasonal variation in amounts. This can be compared to the higher rainfall of the subantarctic islands (1-2 m per year), or the dry interior of the continent, which is virtual desert with only 10 cm precipitation per year. Farther south on the West coast of the peninsula as well as on the Northeast coast to about 63°S, there is a drier maritime climate. Mean monthly temperatures exceeding 0°C for 1-2 months of summer, falling to -15°C in winter, and precipitation is 35 cm or less with occasional rain (EPA 2001). Climate on the east coast of the peninsula south of 63°S is generally much colder due to the extensive pack ice of the Weddell Sea. Here, mean temperatures exceed 0°C for only 0-1 months of summer and winter means are from –5 to –25°C. Precipitation ranges from 10-15 cm (EPA 2001). The peninsula is bisected by the Antarctic Circle, where approximately 2 hours of twighlight occur during winter days, and there is close to 24 hours of sunshine during summer.
The scattered ice-free areas of the Antarctic Peninsula and West Antarctica west of the Transantarctic Mountains are characterized by low temp, high aridity, and a short growing season. Cryptograms- mosses and lichens- dominate the vegetation of the Antarctic tundra. Vegetation of the Antarctic Peninsula’s botanic zone is similar to the feldmark vegetation of the island highlands in the subantarctic botanic zone (Watson et al. 1975). These closed cryptogamic communities occur in protected areas at lower elevations. The primary ground cover is a tundra cushion of moss and lichens in which the continent’s only two lesser flowering plants, or phanerograms, occur: Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis) (Watson et al. 1975). Generally occurring on north-facing slopes on moist soils rich in nutrients, these vascular species occur in sheltered locations as far south as Neny Island, 68° 13'S. Deschampsia may form a ‘sward’ of several meters square, while Colobanthus forms discrete cushions (Fogg 1998). Both species can produce viable seeds, though do not do this every year, so vegetative reproduction is crucial. Birds may uproot portions that are redistributed and established elsewhere (Fogg 1998). Mammals and birds have a significant effect on vegetation despite the fact that none are herbivores. Elephant seals flatten grass area and form wallow pools, and large bird rookeries are devoid of vegetation aside from alga sheets that occur on damp ground rich in bird excrement. Burrowing petrel species generally do not damage vegetation, but rather increase soil aeration and drainage.
In milder and wetter parts of the maritime Antarctic, extensive, shrubby lichen communities will cover favorable rocky areas. Approximately 200-300 lichen species are believed to occur in Antarctica as a whole, and dominant species are 25 shrub-like species in the generas Usenea and Bryoria (Purvis 2000). Lichens may grow faster in areas rich bird excrement, and can also be found growing on human trash, such as broken glass bottles. Lichens appear to be adapting to the ozone depletion an increased levels of UV-B radiation (Purvis 2000).
The mixed tundra vegetation of Deschampsia antarctica, Colobanthus quitensis, mosses, lichens and green algae is richest on the islands scattered off of the west coast of the peninsula. In particularly suitable spots, moss cushions may be as thick as 1 m. The vegetation on rocks and unstable soil generally consists of open communities of lichens and moss cushions, while dry, stable slopes and cliff edges have extenxive moss turf. Lush moss carpets or hummocks grow where water tends to accumulate. In all, approximately 300 species of algae, 200 lichens, 85 mosses, 25 liverworts, and 2 flowering plants are thought to be native to the Antarctic continent.
Biodiversity Features
It is interesting to compare Antarctica’s ecosystem with that of the Arctic region: Antarctic has more available liquid water, and hence tundra has slightly higher biomass and primary production rates. However, the isolation of Antarctica has led to quite different assemblage of species. About 900 vascular plants are native in the Arctic, while there are only 2 in Antarctica (Fogg 1998). The Arctic has 48 species of native land mammals; Antarctica has none. Among bryophytes and lichens there are a few cosmopolitan species, and a definite bipolar element exists, especially in the case of lichens. Explanations for this might be long-distance transport of propagules via mountaintops across the tropics, or possibly survival of species from the time when Gondwanaland was still linked to the northern land masses (Fogg 1998). The difference in species is also due to Antarctica’s cold, oceanic climate, compared to the Arctic’s continental/sub-alpine climate. In general, Arctic has short, favorable growing seasons, while Antarctica has longer, cool, wetter growing seasons. The absence of carnivores allows for the presence of seven species of penguin in Antarctica (Fogg 1998). These birds are all flightless and nest ashore in large colonies that would be very vulnerable to predators. Three species of seal breed ashore in Antarctica, whereas none do in the Arctic. Their presence has some impact on the flora (Fogg 1998).
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) (EPA 2001). Elephant seals are found in the Antarctic Peninsula area and on subantarctic islands, but do not range as farther south into continental Antarctica. 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. Weddell, crabeater, Ross, and leopard seals are all ice-breeding. Seals hauling out on land can have a significant impact on vegetation communities. Pushed almost to extinction by intensive hunting in the 19th century, the fur seal has recovered greatly starting around 1970, and now totals about 1 million individuals (Fogg 1998). The crabeater seal is the most abundant seal in the world, with total population of over 30 million.
Thirty-seven flying seabird species are native to Antarctica (EPA 2001). Some species characteristic of Marielandia are southern fulmar (Fulmaras glacialoides), southern giant fulmar (Macronectes giganteus), cape pigeon (Daption capense), snow petrel (Pagodroma nivea), Wilson’s storm petrel (Oceanites oceanicus), blue-eyed shag (Phalacrocorax atriceps), American sheathbill (Chionis alba), south polar skua (Catharacta maccormicki), brown skua (Catharacta lonnbergi), southern black-backed gull (Larus dominicanus), and Antarctic tern (Sterna vittata) (Watson et al. 1975). These birds must nest on ice-free areas, therefore, they are seldom found far inland over the ice cap, and breed during summer months when coastal areas are exposed. Several petrel species build burrows to nest in the ground.
Of the estimated total of 350 million birds of all species in the Antarctic, about 175 million are penguins. Six species of penguin are 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) (EPA 2001). The chinstrap and gento penguins breed primarily on the milder Antarctic Peninsula. Penguins likely could not exist if carnivores such as polar bears, arctic foxes, or arctic wolves were present.
Certain areas of Marielandia have special status due to unique ecological features. The Dion Islands, in Marguerite Bay (67°52'S, 68°43'W) is a group of small, rocky, low-lying islands, about 13 km south of Adelaide Island. The only colony of Emperor penguins known to exist on the west side of the Antarctic Peninsula is found here, and the isolation of this colony from others of the same species makes it of outstanding scientific interest (Headland 1996). It is also the most northerly and probably the smallest Emperor penguin colony, and one of only two in which the colony breeds on land (Headland 1996). Adelie penguins and blue-eyed shags also breed here.
Lagotellerie Island, also in Marguerite Bay (67°53'S, 67°24'W) lies about 3 km west of the southern part of Horseshoe Island. Lagotellerie contains a relatively diverse flora and fauna typical of the southern Antarctic Peninsula, and is particularly interesting due to an abundance of Deschampsia antarctica and Colobanthus quitensis (the only two Antarctic flowering plants), which form stands up to 10 m2 (Headland 1996). These are some of the largest stands known south of the South Shetland Islands, and occur only 90 km north of their southern limit. The plants flower profusely producing seeds with a greater viability than those in the South Orkney and South Shetland islands. Numerous mosses and lichens also form well-developed communities on the island, with a few of fertile mosses (a rare phenomenon in most Antarctic localities) (Headland 1996). The invertebrate fauna of this community is rich, claiming one of the southernmost sites for the apterous midge (Headland 1996). Additionally, there is a colony of about 1000 Adelie penguins, one of the farthest south colonies of blue-eyed shag, and many pairs of brown and south polar skuas breeding on the island (Headland 1996). Avian Island, Marguerite Bay (67°46'S, 68°54'W) is specially protected due to its abundance and diversity of breeding seabirds, the most important of which are Adelie penguin, blue-eyed shag, southern giant petrel, Dominican gull, skua, and Wilson's storm petrel (Headland 1996).
Current Status
The Antarctic Treaty applies to the area south of 60° south latitude, including all islands and ice shelves. The whole area is subject to Agreed Measures for the Conservation of Antarctic Flora and Fauna which are consolidated in the Protocol on Environmental Protection to the Antarctic Treaty. These include prohibitions on the killing, wounding, capturing or molesting of any native mammal or native bird except in accordance with a permit; and regulations on the importation of exotic species, parasites, and diseases. Permits may be issued only by persons authorized by a participating government Additionally, numerous conservation areas are designated in several categories, and carry further regulation. For example, vehicles are prohibited to enter Specially Protected Areas (Headland 1996).
The Antarctic Treaty has, for the time being, put a ban on any 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. The vast majority of tourism is concentrated at the more accessible and more hospitable Antarctic Peninsula, primarily being cruise ship tours. Overflight tours are also poular, and have a minimal impact on the local environment. Tourism in the Antarctic region dates back to 1891, when the first tourists were passengers on resupply ships to the subantarctic islands (EPA 2001). The first tour group visited the South Pole in 1988 by means of land-based flight operations (EPA 2001). From 1983-93, a hotel, the Estrella Polar Guest House, operated on King George Island off of the west coast of the peninsula (EPA 2001). Tourism is now, in fact, the primary non-governmental activity on the continent. While the majority of Antarctic tourists are highly educated and mindful of conservation issues, the continent’s fragile environment is vulnerable to very low levels of interference. Another issue is that private yachts also travel to Antarctica in increasing numbers since the 1980s. These activities were rarely recorded in the past, and are more difficult to regulate.
Types and Severity of Threats
As the last unspoiled continent on the planet, conservation in Antarctica is far more organized and effective than anywhere else on Earth. While the primary future threat to the Antarctic Peninsula region comes from a likely increase in tourism, other potential threats to the environment will probably 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 (Fogg 1998). It is believed to be the result of widespread use of CFC’s (chloroflurocarbons) 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 persistance 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 (Fogg 1998).
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 (Purvis 2000). 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 (Purvis 2000).
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 (Fogg 1998).
Justification of Ecoregion Delineation
Udvardy (1975, 1987) differentiates two antarctic provinces within the Antarctic continent. The West Antarctic Province, or Marielandia, from Marie Byrd Land in the southwest sector, encompasses the Antarctic Peninsula. The ecoregion boundary corresponds to coastal fringes and associated islands that are free of permanent ice.
References
EPA. 2001. Chapter 2: Affected Environment - the Physical and Biological Environment. Final Environmental Impact Statement for the Proposed Rule on Environmental Impact Assessment of Nongovernmental Activities in Antarctica. Retrieved (2001) from: <http://es.epa.gov/oeca/ofa/antarc/ch_02.pdf>.
Fogg, G.E. 1998. The Biology of Polar Habitats. Oxford University Press, New York, N.Y.
Headland, R.K. 1996. Protected Areas in the Antarctic Treaty Region. Retrieved (2001) from: <http://www.spri.cam.ac.uk/bob/protect.htm#aa>.
Purvis, W. 2000. Lichens. Smithsonian Institution Press, Washington, D. C.
Udvardy, M.D.F. 1975. A classification of the biogeographical provinces of the world. IUCN Occasional Paper No. 18. International Union of Conservation of Nature and Natural Resources, Morges, Switzerland.
Udvardy, M.D.F. 1987. The Biogeographical Realm Antarctica A Proposal. Journal of the Royal Socirty of New Zealand 17:187-194.
Watson, G.E., J.P. Angle, and P.C. Harper. 1975. Birds of the Antarctic and Sub-Antarctic. American Geophysical Union, Washington, D. C.
Prepared by: Leann Trowbridge
Reviewed by: In process