Bouvetøya rises to 780 m a.s.l. (Olavtoppen) and is bounded by steep slopes on the northern, western and south-western sides, with narrow beaches. Permanent ice covers 93% of the island, leaving only a few ice-free areas along the coast. The largest such area is Nyrøysa, which was formed between 1955 and 1958, probably by a large landslide. The Nyrøysa platform is c.700 m long with an average height of between 25 and 40 m. The surface is irregular, consisting of jumbled boulders, lava blocks and gravel. Inland, the platform is bounded by scree slopes created by rockfalls from the high (c.150 to 350 m) cliffs and, at the southern and northern ends, by the shingle-beaches of Westwindstranda. Abrasion by the action of the sea on the seaward cliff of Nyrøysa above Westwindstranda is pronounced and ongoing, with an estimated 50-100 m lost from 1966-1979, and 6-9 m disappearing in places from 1996-1997 to 1998-1999. All recent research expeditions to Bouvetøya have been based at Nyrøysa, since it is the most accessible part of the island and supports breeding populations of seabirds and seals.The vegetation of Bouvetøya is entirely non-vascular, and consists of ascomycete fungi and lichens, and mosses and liverworts (Bryophyta). Algae are also represented. Engelskjøn (1981) classified the vegetation of Bouvetøya into 20 communities, including those of snow algae on glaciers and two of marine algae in the littoral zone. It is of typical maritime Antarctic composition and structure, and bears phytogeographical affinities with the vegetation of more westerly peri-Antarctic archipelagos such as the South Sandwich and South Shetland Islands. Owing to the extensive ice-covering of Bouvetøya, vegetation is largely restricted to the coastal cliffs, capes and boulderine beaches, and the few ice-free nunatak ridges and sections of summit plateau. However, most ice-free areas are so steep and exposed to avalanches that only crustose lichen and algal formations are able to persist. Five species of moss, five lichens, one fungus and 20 algae have been recorded at Nyrøysa. Here, the manuring from seabirds and seals promotes development of algal Prasiola and Ulothrix communities but, where trampling from penguins and seals occurs, no macro-vegetation is able to exist.
See box for key species. To date, 12 bird species - all seabirds - have been recorded breeding on Bouvetøya. These are Pygoscelis antarctica, Eudyptes chrysolophus, Fulmarus glacialoides, Daption capense,Pachyptila desolata, Oceanites oceanicus, Fregetta tropica and Catharacta antarctica lonnbergi, together with Pygoscelis adeliae, Macronectes giganteus, Pagodroma nivea and Sterna vittata for which, however, there are no recent confirmed breeding records. The infrequency of surveys, however, means that it is possible that these latter species continue to breed undetected, and also hampers whole-island population estimates of confirmed breeding species. In addition, Pachyptila belcheri is currently thought to breed at Nyrøysa, and Larus dominicanus has been suspected of breeding in the past.Up to 100,000 Fulmarus glacialoides are estimated to breed on cliffs at, in particular, Kapp Valdivia, Kapp Circoncision, Nyrøysa, and the south-west part of the island from Norvegiaodden to Rustadkollen. Nyrøysa alone supports up to 1,000 breeding individuals of Fregetta tropica. Other than at Nyrøysa, the major penguin colonies on Bouvetøya are situated at Posadowskybreen, Kapp Circoncision, Norvegiaodden and opposite Larsøya (a small rocky offshore islet situated to the south-west of Bouvetøya). The Kapp Circoncision colony is the largest, with an estimated 25,000 individuals recorded in 1989-1990. In 1978-1979 there were an estimated 117,000 penguins on Bouvetøya, the majority being Eudyptes chrysolophus, with Pygoscelis antarctica making up the bulk of the remainder; in 1989-1990 the estimate was 62,125 individuals.Nineteen species have been recorded as summer visitors to the island and its nearby waters: Aptenodytes patagonicus (moulters), Diomedea exulans, D. melanophris, D. chrysostoma, D. chlororhynchos, Phoebetria fusca, P. palpebrata, Macronectes halli, Thalassoica antarctica, Halobaena caerulea, Pterodroma mollis, P. brevirostris, P. lessonii, Pachyptila turtur, Procellaria aequinoctialis, Puffinus gravis, Pelecanoides urinatrix, Catharacta maccormicki and Stercorarius parasiticus.
Non-bird biodiversity: No recognized globally threatened or endemic animal taxa occur at Bouvetøya, but at least three endemic ascomycete fungus species have been recorded, as have three lichen species, including an endemic genus Bouvetiella. Other plant and invertebrate species are restricted to a few other Antarctic sites (e.g. South Georgia, South Orkney Islands) and thus can be considered near-endemics. Breeding by the seal Mirounga leonina at Bouvetøya was reconfirmed in 1998-1999 for the first time in many years; 88 weaned pups were counted at Nyrøysa in December 1998. In January 1999 there were an estimated 13,010 live pups of the seal Arctocephalus gazella at Nyrøysa. The whale Megaptera novaeangliae (VU) was frequently sighted from Nyrøysa in the summers of 1996-1997 and 1998-1999, and Orcinus orca (LR/cd) has been recorded previously.
Pressure/threats to key biodiversity
The whole island is a Nature Reserve. In 1997 Nyrøysa, incorporating the platform and northern and southern beaches of Westwindstranda, was declared a CCAMLR Ecosystem Monitoring Programme (or CEMP) site. This is as part of the CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources) objective of establishing a network of sites throughout the southern ocean for conducting long-term monitoring studies of the foraging ecology, demography and population trends of vertebrate predator populations. A draft management plan exists for Nyrøysa, but is not yet in force. Norwegian and South African biologists have cooperated in three CEMP expeditions to date, in 1996-1997, 1998-1999 and 2000-2001, when monitoring of Eudyptes chrysolophus, Pygoscelis antarctica and Arctocephalus gazella was undertaken.Surveys at Nyrøysa indicate an annual decline of 4.8% in penguin numbers between 1979–1980 and 1989–1990, while more recent data suggest an accelerated decline since then. Infrequent aerial surveys also suggest that declines may have continued elsewhere on the island in the 1990s. A contributing factor to decreases at Nyrøysa has been the expansion, in recent years, of the population of fur seals Arctocephalus gazella. Fur seals impact upon penguins in at least three ways: interference competition on land for breeding territories, incidental injury and mortality in disputes over breeding territories, and predation at sea. However, inferred long-term declines elsewhere on the island, where fur seals do not breed, suggest that larger-scale impacts such as oceanographic change or competition for food might also be important contributory factors. Expansion of the fur-seal colony at Nyrøysa has also resulted in destruction of Brachythecium moss hummocks and the cessation of breeding by Macronectes giganteus.Since Nyrøysa is one of the most important areas for breeding birds on Bouvetøya, the continuing loss of the seaward cliff is of concern. Should the platform retreat until nothing but the inland scree slope remains, it is conceivable that most, if not all, breeding by Pygoscelis antarctica, Eudyptes chrysolophus,Pachyptila desolata, P. belcheri, Oceanites oceanicus, Fregetta tropica and Catharacta antarctica lonnbergi will cease at Nyrøysa.
BirdLife International (2019) Important Bird Areas factsheet: Bouvetøya (Bouvet Island). Downloaded from
http://www.birdlife.org on 16/12/2019.