The subantarctic Prince Edward Island group, consisting of Marion Island (46°54’S 37°45’E; 290 km²; max. elevation 1,230 m) and Prince Edward Island (46°37’S 37°57’E; 44 km²; 672 m), lies in the southern Indian Ocean, c.2,300 km south-east of Cape Town and 250 km north of the Antarctic Polar Front. The islands are surrounded by steep coastal cliffs, between 5 m and 500 m high, with very few beaches. A large proportion of the islands consist of poorly drained coastal plains and slopes.
See Box for key species. Twenty-nine species of bird, 28 of them seabirds, are thought or known to breed at the Prince Edward Islands. Only one other island group in the southern Oceans, the Crozets, holds more species of breeding seabird. The Prince Edward Islands are estimated to support c.2.5 million pairs of breeding seabirds and may support up to 8 million seabirds in total. The islands hold c.15% and 5% of the global populations of Aptenodytes patagonicus and Eudyptes chrysolophus respectively. Numbers of both species are thought to be stable. The islands also support a large proportion of the population of Eudyptes chrysocome. Large numbers of breeding albatrosses occur, including 36% of the breeding population of the globally threatened Diomedea exulans, which was recently split from other ‘Great Albatross’ forms (D. dabbenena, D. gibsoni and D. antipodensis). The islands also hold breeding Diomedea chlororhynchos (this form was recently split to become Thalassarche carteri), 9% of Diomedea (now Thalassarche) chrysostoma and 18% of Phoebetria fusca populations. Extremely large numbers of Pachyptila salvini and Pterodroma petrels breed on the islands, as do small numbers of Pygoscelis papua (1,755 pairs), Pachyptila turtur (100s of pairs), Garrodia nereis (breeding possible, but not proven), Pelecanoides georgicus (100s of pairs) and the endemic subspecies Chionis minor marionensis, which appears to be declining on Marion Island.
Non-bird biodiversity: Elaphoglossum randii, a small fern that grows on black lava-flows, is endemic to the Prince Edward Islands. Several other plant species, such as Ranunculus moseleyi, Polystichum marionense, Poa cookii, Colobanthus kerguelensis and Pringlea antiscorbutica are shared with the Crozet and Kerguelen groups. A high incidence of local and provincial endemism exists amongst the hepatic flora. At least eight species of insect are endemic to the Prince Edward Islands. Increasing populations of the seals Arctocephalus tropicalis and A. gazella occur on the islands, as does a rapidly declining population of Mirounga leonina.
BirdLife International (2019) Important Bird Areas factsheet: Prince Edward Islands Special Nature Reserve. Downloaded from http://www.birdlife.org on 12/12/2019.