South Georgia and its associated smaller offshore islands, islets and stacks lie between the parallels of 53 30S and 55 00'S, and between the meridians of 34 30'W and 42 00'W. These islands are very isolated, lying about 1400 km east-south-east of the Falkland Islands, 1550 km north-east of Cape Dubouzet (the nearest point on the Antarctic continent), 2150 km east of Dungeness (South America's nearest mainland point) and 4800 km from Cape Town, South Africa. The nearest land is Zavodovski Island, the northernmost island in the South Sandwich Islands group, 550 km to the east-south-east.
South Georgia holds one of the world's most abundant and diverse seabird communities, whose total breeding population probably exceeds 30 million pairs. The most abundant species on the island are Macaroni Penguins, Antarctic Prions and Common Diving Petrels with more than two million pairs estimated for each. White-chinned Petrels, and Blue Petrels may also number over 1 million pairs, but estimates for these two species are imprecise. A total of 31 bird species has been recorded breeding, of which 25 are seabirds. Of these, there are six species of penguin, four species of albatrosses and 13 species of smaller petrels and related species, including 9 burrow-nesting petrels. There is one landbird, an endemic passerine, the South Georgia Pipit and there are 5 waterbird species including two species of waterfowl, the Yellow-billed Pintail (South Georgia Pintail) and the Speckled Teal, the latter believed to be a relatively recent arrival from South America or the Falkland Islands. Three endemic subspecies/taxa have been recognised. They are the Yellow-billed Pintail (South Georgia Pintail)and the Imperial Cormorant (South Georgia Cormorant)which are confined to the island group, and the Antarctic Tern (South Georgia Tern). Forty five species of vagrant migrants have been recorded from the island and its inshore waters, including a number of waders. Ten species of global conservation concern breed at South Georgia. These are the Endangered Black-browed Albatross, Vulnerable Wandering Albatross, Grey-headed Albatross, Southern Giant Petrel and White-chinned Petrel; and also the Near-Threatened Gentoo Penguin, Macaroni Penguin, Light-mantled Albatross, Northern Giant Petrel and South Georgia Pipit. The island is a Secondary Area (s037) because of the restricted-range South Georgia Pipit, which is confined to South Georgia and its offshore tussac islands. Seven Procellariidae taxa are protected under the Agreement for Conservation of Albatrosses and Petrels (ACAP). They are the Wandering Albatross, Black-browed Albatross, Grey-headed Albatross, Southern Giant Petrel, Northern Giant Petrel and White-chinned Petrel. In global terms, South Georgia is the most important breeding site for Grey-headed Albatrosses and White-chinned Petrels, the second most important site for Wandering Albatrosses (after the Prince Edward Islands) and King Penguins (after Crozet Islands); and the third most important site for Black-browed Albatrosses (after the Falkland Islands and Chile). Well over half of the world population of White-chinned Petrels, Grey-headed Albatrosses, Antarctic Prions and Common Diving Petrels breed here, as do nearly half of King Penguins and Gentoo Penguins and possibly Blue Petrels, and around one quarter of Macaroni Penguins (subject to revision as the population has declined significantly in recent years), Northern Giant Petrels and Brown Skuas Wandering Albatrosses and Snowy Sheathbills account for 20% of the world populations and Black-browed Albatrosses and Southern Giant Petrels for approximately 15%.
Non-bird biodiversity: Antarctic fur seals Arctocephalus gazella (3 million individuals and increasing), southern elephant seals Mirounga leonina (400,000 individuals) and Weddell seals Leptonychotes weddelli (30 adult females) breed on South Georgia. Leopard seals Hydrurga leptonyx and crabeater seals Lobodon carcinophagus are regular visitors. There are no endemic plants. About one third of the 230 species of arthropod fauna are endemic. One species is preyed upon by an introduced carabid. All insects are at risk of predation by rats and mice. There are 70 species of freshwater invertebrates and 6 species of spiders. The coastal waters are inhabited by small numbers of Orcinus orca (LR/cd), Eubalaena australis, Balaenoptera musculus, B. physalus, B. borealis, B. acutorostrata, Megaptera novaeangliae, Physeter catodon, Hyperoodon planifrons, Globicephala melas, Lagenorhynchus cruciger, Australophocaena dioptrica, and unidentified beaked whales.
The site includes 2 Areas of Special Tourist Interest, 2 Sites of Special Scientific Interest (SSSI) and 1 Specially Protected Area (SPA), all proclaimed in 1975. The 2 SSSIs and SPA have been included in the list of 5 proposed Protected Areas, and all rat-free areas have been proposed as Environmentally Sensitive Areas, but without enforcing legislation. Predation on seabirds by rats, overgrazing of native vegetation by reindeer and the introduction of alien plants and insects are altering the native flora and fauna of large areas of the site. The greatest and most immediate threat to the environment is the introduction and spread of Norway rats. Despite the unique biodiversity of South Georgia's rodent-free areas, the majority of them and notably the entire rat-free mainland coast are completely unprotected. Increased glacial retreat and global warming may present additional potential threats if ice barriers that currently isolate rat-free areas disappear. Rats were successfully eradicated from Grass Island (30 ha.) in 2000 and the Government has expressed an intention to support further eradication programmes, including extirpation of at least one of the two herds of introduced reindeer. Other threats include unlicensed fishing within the Maritime Zone, pollutants from vessels passing through territorial waters and more critically, those that are wrecked on the islands' shores, and the dispersal of pollutants from the abandoned whaling stations (believed to be minimal). Trawl and longline fisheries are believed to be a major cause of mortality of South Georgia's Wandering, Black-browed and Grey-headed Albatrosses and White-chinned Petrels. Fishing activity within the Maritime Zone around South Georgia is regulated by internationally adopted measures agreed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Measures taken to reduce the number of birds killed within the Zone have proved to be extremely effective and regular fisheries surveillance ensures there are no illegal or unregulated fishing activities. However, it is apparent that fishing activities outside the Zone continue to be responsible for significant numbers of deaths, with over 4% of breeding Wandering and Black-browed Albatrosses killed annually. Indiscriminate use of deck and ice lights on board any type of vessel presents considerable risks to the island's burrowing petrel populations and there are several reports of large numbers of burrowing petrels of several species being killed by bird strike. Expansion of the fur seal population at South Georgia has significantly impacted seabirds in areas of high seal density, through destruction of breeding habitat in tussac grassland. Burrow-nesting petrels, South Georgia Pintail and South Georgia Pipits are particularly affected if the loss of protective foliage cover leads to increased skua predation. Burrow entrances may be blocked or damaged by seals, and courting Wandering Albatrosses abandon traditional display sites. The constant disturbance from repeated passage of seals has resulted in a redistribution of nest sites for this species and for giant petrels in certain areas.