The Antarctic mainland is relatively poor in plant life, and the species that occur there have to survive extreme conditions on the very few ice-free pieces of land. There are no trees or shrubs in the Antarctic, and only two flowering plant species, the Antarctic hair grass (Deschampsia antarctica) and the Antarctic pearlwort (Colobanthus quitensis), which grow on the Antarctic Peninsula and some Antarctic islands (1) (3).
Most of the terrestrial plant life of the Antarctic consists of lower plant groups, such as mosses, liverworts and lichens. Lichens and some mosses can be found growing even on windswept, dry rock surfaces, and are well adapted to survive the harsh climate (1) (2) (3). A number of fungi species are also found in the Antarctic (1) (3).
Although poor in higher plants, the Antarctic does support single-celled algae, which grow both on land and in the ocean, where they contribute to the ‘phytoplankton’ that are an important part of the marine food chain (1). Algae can even be found growing on ice and snow (1) (2), often colouring it red, green or orange (1).
The milder, wetter sub-Antarctic islands are more suitable for plant growth, and most have a slightly more diverse range of flowering plants and ferns (3) (5) (13) (14) (16). These include tussock grass, a tall, robust plant which often forms the tallest vegetation cover (3) (14). Human activities on these islands have also led to many non-native plant species being introduced (3) (16).
There are no naturally occurring land mammals in the Antarctic, but the surrounding oceans are home to a rich diversity of marine mammals. Of the six Antarctic seal species, the leopard seal (Hydrurga leptonyx), Ross seal (Ommatophoca rossii), Weddell seal (Leptonychotes weddellii) and crabeater seal (Lobodon carcinophaga) are ice habitat specialists, breeding on the sea ice in spring (1) (3). The Weddell seal breeds further south than any other mammal (4). Other species, including the Antarctic fur seal (Arctocephalus gazella) and southern elephant seal (Mirounga leonina), are found further north (1) (3). All Antarctic seal species are well adapted to the cold, with thick layers of blubber and insulating fur (3) (6).
The Southern Ocean around Antarctica is also home to many species of cetacean, including the Antarctic minke whale (Balaenoptera bonaerensis), sperm whale (Physeter macrocephalus), fin whale (Balaenoptera physalus), southern right whale (Eubalaena australis), humpback whale (Megaptera novaeangliae), orca (Orcinus orca), and the largest animal in the world, the blue whale (Balaenoptera musculus) (1) (4) (6). The region’s dolphins include species such as the hourglass dolphin (Lagenorhynchus cruciger) (15).
Most whale species around Antarctica are migratory, moving north to warmer waters in winter to give birth, and returning again in the spring to feed in the rich waters of the Southern Ocean (1) (3) (6).
Although the sub-Antarctic islands also lack native land mammals, humans have introduced a variety of non-native species, including rats, mice, cats, rabbits, sheep and reindeer, often with damaging impacts on native species (3) (4) (9) (14) (17).
Perhaps some of the most iconic of Antarctic species are the penguins. All penguin species are restricted to the southern hemisphere (1) (2) (3), but only two, the emperor penguin (Aptenodytes forsteri) and Adélie penguin (Pygoscelis adeliae), are considered to be truly Antarctic, breeding on the Antarctic continent. However, two other species, the chinstrap penguin (Pygoscelis antarcticus) and gentoo penguin (Pygoscelis papua), can be found on the milder parts of the Antarctic Peninsula and on islands around the Antarctic (1) (3) (5) (6), while other penguin species, including the king penguin (Aptenodytes patagonicus) and macaroni penguin (Eudyptes chrysolophus), occur further north on sub-Antarctic islands (1) (3) (4) (6). As well as being well adapted to swimming and diving, penguins have a range of adaptations to the cold, including a thick layer of fat beneath the skin and overlapping layers of waterproof feathers (1) (2) (3) (4) (6).
The Antarctic and sub-Antarctic waters also support vast numbers of seabirds, with the Antarctic and sub-Antarctic islands providing vital breeding grounds for many species. Seabirds in the region include albatrosses such as the wandering albatross (Diomedea exulans) and black-browed albatross (Thalassarche melanophrys), petrels such as the Antarctic petrel (Thalassoica antarctica) and snow petrel (Pagodroma nivea), and a variety of shearwaters, skuas and gulls (1) (3) (4).
The Antarctic region has few endemic terrestrial birds. The island of South Georgia is home to the only songbird in the Antarctic, the South Georgia pipit (Anthus antarcticus), as well as to the South Georgia pintail, an endemic subspecies of the yellow-billed pintail (Anas georgica) (3) (4) (16). A number of other land birds are found on other sub-Antarctic islands, including the New Zealand Sub-Antarctic Islands (13) and on the island of Macquarie (14).
Reptiles and amphibians
There are no reptile or amphibian species in the Antarctic (3).
Fish and invertebrates
There are around 200 fish species in the Antarctic region (2) (4), most of which are slow-growing and have unique adaptations to the cold (2). The majority of Antarctic fish come from the Nototheniidae family, commonly known as the Antarctic cods, which includes species such as Notothenia nudifrons and Notothenia coriiceps (2) (3) (4). Many of these species possess ‘antifreeze’ substances in their blood (1) (2) (3) (4) (9).
Other Antarctic fish include the Antarctic toothfish (Dissostichus mawsoni), the Patagonian toothfish (Dissostichus eleginoides) and the mackerel icefish (Champsocephalus gunnari) (1) (4). Icefish (Channichthyidae species) are the only vertebrates which lack the red oxygen pigment haemoglobin in their blood (1) (2) (3) (4) (9). As a consequence, these intriguing fish have clear blood and pale flesh (1) (2) (3).
The terrestrial invertebrate fauna of the Antarctic continent is relatively poor, consisting mainly of species such as springtails, mites and nematode worms (1) (2) (3). However, the population densities of these species can often be high (3). On the milder sub-Antarctic islands, a range of other species can be found, including spiders, beetles, earthworms and flies (1) (3).
In contrast, the waters around Antarctica are home to a wide variety of invertebrates, including crustaceans, amphipods, worms, molluscs, sponges, corals, and echinoderms such as the sea star (Odontaster validus) and Antarctic sea urchin (Sterechinus neumayeri) (1) (2). The rich phytoplankton below the sea ice provides an abundant food source for many species, and in some areas an incredible 155,000 animals have been recorded per square metre of sea bed (1). Many species, such as the giant Antarctic isopod (Glyptonotus antarcticus), are unusual in being particularly large compared to their relatives in other parts of the world (1).
Large numbers of squid are also found around the Antarctic, including the large giant squids of the genus Architeuthis (2) (3). The squid in turn provide food for a range of predators, from seabirds to sperm whales.
Perhaps the most important species in the Antarctic is the Antarctic krill (Euphausia superba). This small, shrimp-like crustacean lives in dense swarms and is one of the most abundant and successful animals on the planet. Despite its small size, krill is vital to the Antarctic food chain, providing the staple food for a wide range of fish, whales, seals, penguins and seabirds (1) (2) (3) (4) (9).
A remote, hostile wilderness, the Antarctic remains the most uninhabited continent on Earth, only visited by scientists and tourists (3) (4). However, its fragile and increasingly vulnerable environment has not been unaffected by human activities (1) (3) (5).
The wildlife of the Antarctic has been exploited for many years. Humans were first attracted to the Antarctic by the region’s whales and seals, and many species were severely overexploited (1) (3) (6) (18). Although now largely protected, some of these species will take time to recover from previous declines (3) (6), and may face further threats from marine pollution, disturbance by tourists, competition and interactions with fisheries, and the effects of climate change (18).
Many of the Antarctic’s seabirds are also under threat, mainly from accidental mortality caused by longline fisheries, which use lines of baited hooks on which foraging seabirds can get caught (1) (3) (5). Further threats include pollution, depletion of fish and krill stocks by fisheries, and environmental changes potentially linked to climate change (1) (5). Some penguin populations have also shown large declines, possibly linked to reduced food supplies and changes in sea ice (5).
Introduced, non-native mammals have also had devastating effects on seabird colonies, with rats and cats killing chicks on a number of sub-Antarctic islands (4) (11) (12) (16). On South Georgia, the presence of rats is also driving the endemic South Georgia pipit to extinction, and this species now breeds only on rat-free offshore islands and islets (12) (16).
In addition to introduced predators such as rats and cats, non-native grazing animals such as reindeer and rabbits are destroying native vegetation and altering habitats on many sub-Antarctic islands, while introduced, non-native plants are also spreading (9) (14) (16) (17). The remoteness and harsh climate of the Antarctic continent have largely limited the impact of introduced species. Some invertebrate and plant introductions have occurred, but these species have not yet become established (3).
Commercial fishing in the Southern Ocean only began in the 1960s, but was unregulated for the first few decades, resulting in large declines in species such as the marbled rockcod (Notothenia rossii) (1) (3). Fishing regulations are now in place, with the main target species being the Patagonian toothfish (Dissostichus eleginoides) and Antarctic toothfish (Dissostichus mawsoni) (3) (5). However, illegal, unreported and unregulated fishing is still a problem, and undermines efforts to manage fish stocks. Illegal fishing vessels often use destructive fishing techniques, and do not implement measures intended to reduce seabird mortality caused by fishing gear (1) (5) (10).
A developing fishery for krill is also of concern (3). Krill species are increasingly in demand, sometimes for human food products, but more commonly to make feed for farmed fish and for use in nutritional supplements (1) (2) (4) (5). Krill populations have been declining (5), and the krill harvest will need to be carefully regulated if it is not to have severe impacts on the entire Antarctic marine ecosystem (2).
More localised human impacts in the Antarctic include pollution and disturbance to wildlife caused by scientists and other visitors, although strict regulations are now in place to minimise environmental damage (1) (3). Oil spills remain a potential risk (1) (6), and there is concern that the growing number of tourists visiting the region could negatively affect the Antarctic environment (1) (3) (5) (6).
Although oil prospecting and mineral extraction have been banned in the Antarctic (1) (3) (5) (6) (19), ‘biological prospecting’ (investigating the unique properties of Antarctic species for use in commercial or medical products) could potentially become a threat (5) (19). There is also debate about whether scientists should drill into lakes under the ice, such as Lake Vostok, a huge lake over 3,000 metres below the ice. The water in these lakes may be millions of years old, and there are fears that drilling equipment could contaminate this unique and pristine environment (4).
Perhaps the greatest future threat to the Antarctic is global climate change. The Antarctic is vital to many global processes, including water circulation and the uptake of carbon dioxide by the world’s oceans. Environmental changes in the Antarctic could therefore have repercussions around the world (1) (6) (7). Although the effects of climate change in the Antarctic are complex and not fully understood, current models predict that, at current rates, melting of the ice sheet in West Antarctica could contribute to sea level rise of up to 1.4 metres by 2100 (7).
On a more local scale, a reduction in winter sea ice could mean icebergs are more free to drift, causing greater damage to sea bed communities from scouring by ice (20). Increased water temperatures are also likely to alter marine communities (1). For example, king crabs (Neolithodes yaldwyni), a predatory species, are already moving onto the Antarctic shelf and are likely to have significant impacts on other species (21). On land, increased melting is likely to expose new land for colonisation by plants and animals (1) (7).
Increasing levels of ‘greenhouse gases’ such as carbon dioxide, which are believed to be driving global climate change, are also leading to increased ocean acidity. This is a particular problem in the Southern Ocean, as cool water absorbs more carbon dioxide than warmer waters. Increased acidity may affect the ability of marine organisms to form their shells, and so is likely to impact on species such as crustaceans and corals (1) (5) (7).
One of the most significant scientific discoveries in the Antarctic has been the presence of the ‘ozone hole’, a dangerous thinning of the ozone layer in the Earth’s upper atmosphere, caused by the use of chlorofluorocarbons (CFCs). This hole potentially increases the amount of damaging UV radiation reaching the Antarctic region, and may have a significant effect on the Antarctic climate (1) (3) (7).