Location and General Description
Amsterdam and Saint-Paul are subantarctic volcanic islands in the southern Indian Ocean, located approximately 80 km from each other (Jouventin 1994). Among the most remote islands in the world, Amsterdam and Saint-Paul are more than 3,000 km from any continent, situated between Antarctica, Africa, and Australia. Amsterdam (37°50'S, 77°31'E) is an island of about 55 km2, with an extinct volcano reaching 911 m altitude. The island is relatively recent, having formed between 400,000 and 200,000 years ago (Jouventin 1994). Numerous craters and vents are present, though there has been no recent volcanic activity. The western part of the volcano collapsed, forming vertical cliffs of 400-700 m. Saint-Paul is a much smaller island, only 7 km2, and reaching an altitude of 272 m. Saint-Paul’s volcanic crater is striking; it is flooded and open to the sea on one side, creating an enclosed harbor with cliffs rising vertically from the water. Together with the Crozel and Kerguelen archipelagoes and the Antarctic territory of Terre Adèlie, Saint-Paul and Amsterdam are part of the French Southern and Antarctic Territories, formed in 1955.
Approximately 500 km north of the Antarctic convergence, Amsterdam and Saint-Paul have a moderate oceanic climate. Surface seawater temperature varies from 12.7° in August to 17.4° in February. Air temperatures vary from 11.2° in August to 17° in February, with an annual average of 13.5° (Carroll 2001). Relative humidity is generally high due to the frequency of low cloud ceilings, and ranges from 80% in March to 82.9% in November. Rainfall is high with an annual average of 1,114 mm distributed over 239 days and falling primarily as rain. Hail or snow is observed in winter but seldom at low altitudes. December through March is drier (78 mm per month) than April to November (100 mm per month) (Carroll 2001).
The flora of Amsterdam Island is patterned in clearly marked vegetation types according to altitude (Georges 1999). The lowland area originally supported a native Phylica forest mixed with ferns such as Elaphoglosum succaesifolium, Gleichenia polipodioides, and Ploystichum adiantiforme (Jouventin 1994). Also present were flowering plants (Plantago stauntoni, Acaena sanguisorbae) and liverworts (Marchantia spp.), and glades were characterized by rushes (Scirpus nodosus and Juncus australe) (Jouventin 1994). This was broken by the high coastal cliffs to the Southwest, where two grasses (Poa novarae and Spartina arundinacea) and a rush (Scirpus nodosus) were dominant. Highland slopes were characterized by an association of clubmoss (Lycopodium trichiatum), a fern (Gleichemia polypodioides), and flowering plants (Poa fuegiana, Acaena seurguisarbae, Scirpus aucklandicus, Uncinia brevicaulis, and Trisetum insulare) (Jouventin 1994). Ranunculus biternatus and Callitriche antarctica grew in the few areas with running water. The peat-bog of the central plateau, "Plateau des Tourbieres", persists much as it was before human interference; it is chracterized by mosses growing in association with Lycopodium saurusus, Scirpus aucklandicus, Trisetum insulare, and Uncinia compacta (Jouventin 1994).
The vegetation of Saint-Paul island is similar to that of Amsterdam, though with less altitudinal variation and without the presence of the Phylica tree. Grass and tussock grass occur on dry, lower slopes, sedges grow in wetter areas, and the rocky shores of the island are generally covered by introduced, invasive species (UNEP 1998).
Amsterdam and Saint-Paul Islands are typical of many isolated island ecosystems, in that there is a paucity of species in conjunction with a high rate of endemism. The original high endemism of Amsterdam and Saint-Paul Islands’ avifauna was likely a result of its unique biogeographical position. Not only are the islands very isolated, they also have the added factor of being located near subantarctic islands, but in subtropical waters. Species likely emigrated from the colder islands, and then underwent speciation adapting to the markedly different environment of warmer waters. The Tristan da Cunha-Gough Islands lie at the same latitude in the Atlantic Ocean, though oceanic currents result in their waters being colder and not much different than nearby subantarctic islands. Thus, this island group had a lower original endemism rate of seabirds as adaptations were less necessary there than at Amsterdam and Saint-Paul Islands (Jouventin 1994).
Amsterdam Island is the only French subantartic isle that supports a native tree, Phylica nitida. In the Rhamnaceae family, this tree has small, narrow leaves and honey-scented yellow flowers, reaches 6-7 m, and is abundant on the Tristan da Cunha-Gough Island group, a separate ecoregion, in the Atlantic Ocean (Jouventin 1994). An early description of Amsterdam Island from 1726 described an almost impenetrable Phylica forest in a belt around the island at 100 to 250 m covering almost a third of its surface. At present the "Grand Bois" (large forest) is the only thick remnant of Phylica on the eastern coast covering about 8 hectares, or about 0.2% of the whole island (Jouventin 1994). This dramatic reduction was likely the result of cutting, fires and destruction by the cattle that were introduced in the later 1800s and are now wild. The "Grand Bois" has been fenced and bordered by introduced cypresses as protection from the cattle. A few isolated Phylica trees subsist outside of this area either in protected zones or in areas inaccessible to the cattle (Georges 1999). A fern, Hymenophyllum aeruginosum, is a threatened plant native to Amsterdam Island (UNEP 1998).
The original native fauna of Amsterdam and Saint-Paul Islands was quite unique before the arrival of humans. Fossil records show that Amsterdam Island avifauna until recently comprised a likely 22 species (Jouventin 1994). There are currently only 10 or 11 breeding seabird species, of which 4 are extremely rare. The endemic Amsterdam albatross (Diomedea amsterdamensis) is one of the worlds rarest species of avifauna, found only on Amsterdam Island; this remnant population is restricted to the upland Plateau des Tourbières and has only 10 pairs breeding in any single year (Jouventin 1994; Inchausti and Weimerskirch 2001). Individuals breed every other year, and the entire population of Diomedea amsterdamensis is estimated at only 70 individuals (Jouventin 1994). Thus, this species is considered to be under serious threat of extinction. Macgillivray’s race of Salvin’s prion (Pachyptila salvini macgillivrayi) is an subspecies endemic to the ecoregion with less than 200 breeding pairs. Once very abundant on Amsterdam and Saint-Paul, Pachyptila salvini macgillivrayi, with its distinct wide blue beak, has significantly decreased in number on Amsterdam Island. The species has also retreated to breed on Roche Quille (150-200 pairs), a small rock offshore of Saint-Paul that is safe from predators (Jouventin 1994). One of the most abundant species on the islands is the yellow-nose albatross (Diomedia chlororhynchos). This ecoregion supports approximately 80% of the world’s population, or about 37,000 breeding pairs (Jouventin 1994; UNEP 1998). Other residents of the islands are sooty albatross (Phoebetria fusca) (240 pairs), remnant populations of soft-plumaged petrel (Pterodroma mollis) and grey petrel (Procellaria cinera), antarctic tern (Sterna vittata tristanensis), brown skua (Catharacta lonnbergi), and common waxbill (Estrilda astrild) (introduced 1977-1985) (Jouventin 1994). Of the species that disappeared, four were probably endemic; these were a flightless duck and a storm-petrel, both undescribed, and likely two petrels of the genera Pterodroma and Procellaria (Jouventin 1994).
Another resident of this island group is the rockhopper penguin (Eudyptes chrysocome moseleyi). Rockhoppers in the northernmost breeding region of Amsterdam, Saint-Paul and Tristan-Gough Islands form the distinct moseleyi subspecies, which have longer crests than their colder climate relatives. Quite an unusual looking creature, these penguins have orange-red bills and bright red eyes in addition to their elaborate yellow and black crests.
Seals have long used Amsterdam and Saint-Paul Islands, and were once so numerous that reports stated that their multitudes made landing impossible. The subantarctic fur seal (Arctocephalus tropicalis) continues to breed on the islands, and had an estimated 20,000 adults in 1981 (UNEP 1998). While the southern elephant seal (Mirounga leonina) no longer breeds on the islands, its numbers have been increasing (UNEP 1998). Elephant seals exhibit the greatest sexual dimorphism among all mammals in regard to weight, with males weighing up to five tons whereas females only rarely weigh over one ton (Georges 1999). Both seals were approaching extinction on Amsterdam Island at the beginning of the 20th century but have been recovering since protections were put in place and are now re-established all over the island (Carroll 2001).
Five cattle were introduced to Amsterdam Island in 1871, then increased to about 2,000 individuals in 1987. The herd has been completely naturalized, surviving without humans for over a century. The cattle feed on rushes and withstand the dry season when no surface water is available (Jouventin 1994). Their unusual existence has presented a unique challenge in conservation management, as the cattle are both the main threat to endangered indigenous species as well as one of the very few feral herds of Bos taurus anywhere in the world (Micol and Jouventin 1995). A compromise was made to divide the island with a fence in 1987, with cattle enclosed in the smaller southern section. It is hoped that this will allow the ecosystem to be rehabilitated while preserving the scientific interest of the herd.
Amsterdam Island is the most degraded of the French southern island territory, having suffered drastically during the eighteenth century due to its position in the direct route of ships sailing between South Africa and Australia. Many ships stopped here to collect wood. Between 1792 and 1974, several peat fires occurred on the island (at least four known to have been started accidentally by humans) and further reduced the island’s native Phylica forest (Jouventin 1994). Erosion naturally followed destruction of the forest, eliminating significant habitat for the burrowing petrel species (Jouventin 1994). Invasive plants have also changed the landscape significantly. Lowland meadow now covers most of the area that was once thick with native Phylica forest. Certain plant species were introduced for grazing domestic animals, such as velvetsoft meadow grass (Holcus lanatus) and dandelion (Leontodon taraxacoides), and have flourished due to their ability to withstand the trampling of cattle (Georges 1999). A recent introduction, thistle (Cirsium vulgare), has spread extensively since a 1974 fire (Georges 1999). The residual area of Phylica trees stretches along the island’s eastern slope between the "Grand Bois" (large forest) and the "Chaudron" (the cauldron).
The greatest impact to the island’s fauna occurred during the intensive sealing exploitation which decimated the subantarctic fur seal populations. It is thought that 150,000 fur seals from Amsterdam and Saint-Paul Islands were killed between 1789 and 1835, and their complete disappearance followed in 1893 (Jouventin 1994). Around 1880, fur was no longer in great demand, and eventually the subantarctic fur seal population returned and experienced a rapid regrowth that now appears to have stabilized (Guinet et al. 1994). Human visitors also killed penguin, albatross and petrels for food or fishing bait. Introductions of various animals occurred both accidentally and deliberately. Some such as dogs (Canis familiaris) and pigs (Sus scrofa) disappeared, though pigs likely first caused significant damage by destroying bird burrows and eating eggs. Goats (Capra aegagrus) survived on the island for 100 years, causing severe damage to vegetation, and were eventually eradicated intentionally. Mice (Mus musculus), rats (Rattus norvegicus), and cats (Felis catus) remain and are skilled predators of the native birds. The remaining populations of burrowing petrels, soft-plumaged petrel (Pterodroma mollis) and grey petrel (Procellaria cinera), are hunted by rats and cats; in addition to eating eggs, cats are able to catch adults at the entrance of burrows. However, it is thought that these species recently have had less impact on the reduced bird populations than have the feral cattle, which indirectly harm native birds through destruction of their habitat.
Amsterdam Island was included in the Parc National Antarctique Francais in 1938, and currently houses a small population of 30 or so researchers and military personnel at its scientific and meterological base, which was established in 1949. It was the discovery in 1983 of the relic population of Amsterdam albatross (Diomedea amsterdamensis) that resulted in the establishment of a restoration program (Micol and Jouventin 1995). Several measures have been taken to regain a portion of the biodiversity lost from this ecoregion. It is known that the Amsterdam albatross once bred across a much larger area, and it is hypothesized that indirect competition with the feral cattle population reduced their breeding area, along with other seabirds (Jouventin 1994). Among other benefits, a division of the island and regeneration of the native forest may help the threatened albatross to gain in numbers. The restoration program has begun replanting Phylica trees in the northern section of the island, which is protected from the cattle. A management plan is also in place to control the size of the herd, which has provided meat to the people at the base for some time.
Types and Severity of Threats
Though the impact of fishing activity and pollutants in the vicinity of Amsterdam and Saint-Paul is small due to their extreme isolation, any future increases are a concern. Too large to fall prey to cats, the primary threat to the yellow-nosed albatross is mortality from longline fishing. Studies have concluded that any new long-line fishery operating in the foraging range of the Amsterdam albatross might rapidly put the species at a higher risk of extinction (Inchausti and Weimerskirch 2001).
Justification of Ecoregion Delineation
These relatively young volcanic islands are located more than 3000 km away from any continent. Amsterdam and Saint-Paul are in a unique biogeographic position among islands of the Southern Indian Ocean, in that they are near enough to allow for biodiversity exchange with subantarctic islands, but are in subtropical waters. This situation allowed a significant level of speciation to occur, especially with regard to avifauna.
Carroll, P. 2001. Amsterdam & St Paul Islands, South Indian Ocean. Retrieved (2001) from: <http://www.btinternet.com/~sa_sa/amsterdam/amsterdam.html>.
Georges, J. Y. 1999. Amsterdam Island. Retrieved (2001) from: <http://jygeorges.free.fr/english/menu.html>.
Guinet, C, Jouventin, P, and Georges, J-Y. 1994. Long term population changes of fur seals Arctocephalus gazella and Arctocephalus tropicalis on subantarctic (Crozet) and subtropical (St. Paul and Amsterdam) islands and their possible relationship to El Nino southern oscillation. Antarctic Science 6:473-478.
Inchausti, Pablo and Weimerskirch, Henri. 2001. Risks of decline and extinction of the endangered Amsterdam albatross and the projected impact of long-line fisheries. Biological Conservation 100:377-386.
Jouventin, P. 1994. Past, present and future of Amsterdam Island, Indian Ocean. Pages 122-132 in D. N. Nettleship, J. Burger, and M. Gochfeld, editors. Seabirds on islands: threats, case studies and action plans. BirdLife International (BirdLife Conservation Series no. 1)., Cambridge, U.K.
Micol, Thierry and Jouventin, Pierre. 1995. Restoration of Amsterdam Island, south Indian Ocean, following control of feral cattle. Biological Conservation 73:199-206.
UNEP. 1998. United Nations Environment Programme - Island Directory. Retrieved (2001) from: <http://www.unep.ch/islands/isldir.htm>.
Prepared by: Leann Trowbridge
Reviewed by: In process