The Polynesian Realm
The Polynesian Realm comprises all the islands within the vast expanse of the North and South Pacific east of the Australian, Papua-Melanesian and Indo-Malaysian realms and west of the Americas. Alternatively known as the Oceanian Realm, it is divided into three zoogeographic regions (Polynesian, Novozelandic, and Micronesian). The climatic range is considerable, ranging from tropical to subpolar.
The Polynesian Realm is geologically quite young. While other terrestrial realms include ancient continental landmasses or fragments of continents, it is composed of mostly volcanic high islands and coral atolls that arose from the sea in relatively recent times, many of them during the Pleistocene. They were created either by volcanism or as island arcs pushed upward by the collision and subduction of tectonic plates. Thus, the islands are really tall pillars rising from the depths, constantly exposed to the destructive action of rain, sun, and sea. During countless ages, moreover, myriads of small corals have built up strong walls around almost every island. Sometimes the land has disappeared from inside an encircling atoll, leaving only a lagoon in the centre. Some low islands consist entirely of coral. Plants and animals have colonized and are still doing so both volcanic and coral islands, mainly from the west.
Species and subspecies
The Polynesian sheath-tailed bat (Emballonura semicaudata) as a species ranges across the islands of the western and central Pacific, where it is threatened by loss of habitat and disturbance of its roosting caves. The nominate form (E. s. semicaudata) was historically found sporadically in the Samoan, Fiji, Tongan, and Caroline islands as well as Vanuatu. It has been extirpated from the Samoan Islands and was last collected from the Tonga Islands in 1989, and may now be largely or wholly confined to the Fiji Islands, particularly Rotuma.
The black-footed albatross (Phoebastria nigripes) is a large seabird that ranges throughout the North Pacific Ocean (and occasionally south of the equator as well) but nests only on a dozen islands, virtually all of which are in the isolated northwestern Hawaiian Islands. Additional small colonies are found in a few islands south of Japan and (at least formerly) off the coast of Mexico. At one time heavily hunted, the species has recovered much of its former range and numbers but remains vulnerable to incidental capture from commercial fisheries.
The Laysan albatross (Diomedea immutabilis) is a gull-like species that ranges across the North Pacific from Japan to the Bering Sea and south to Mexico. It is currently confined to just 16 nesting sites, however, the vast majority of which are in the north-western Hawaiian Islands where during the early nineteenth century hundreds of thousands of birds were slaughtered by Japanese feather hunters. The important Wake Island and Johnston Atoll colonies were completely wiped out before protections were finally put in place. While once again common, the species has yet to fully reclaim its former range and numbers, and remains vulnerable to feral cat predation, longline fisheries, and plastic pollution.
The Phoenix petrel (Pterodroma alba) is a type of seabird found throughout the central Pacific, where their breeding colonies are nevertheless highly threatened by habitat destruction, human exploitation, and predation by invasive species.
The Polynesian storm petrel (Nesofregetta fuliginosa) breeds on a number of islands across the central Pacific but is highly vulnerable to introduced predators and other threats. Many of its former colonies have become extirpated.
Bryan’s shearwater (Puffinus bryani) is a rare and little-known type of seabird first described from a single individual collected in 1963 from Midway Island in the north-western Hawaiian Islands. It was not reported again until the early 1990s, when a few more were found in nesting burrows there, and since 2015 has also been found in the Bonin Islands of Japan. Its at-sea distribution remains unknown.
Anthropogenic effects on the flora and fauna
As can be seen, during the two and a half centuries that Europeans have been exploring, trading, whaling, and settling in the island world of the South Seas they have managed to wreak considerable havoc. Considering the small land area these islands represent, the figures are frightening. How much remains now that Western civilization with its diseases, introduced species and commercialization has swept over the region? Because there are thousands of islands there, it is difficult to give a simple answer. Almost every one has its own special character, or at least certain features, even when only a narrow sound separates two neighbouring islands. On isolated islands or in the remote mountain regions of even the larger ones remnants may still be found of the original flora and fauna. Even more alarmingly, the number of native inhabitants continues to grow at an alarming rate. In recent historical time (i.e. since ad 1500), the Polynesian Realm as a whole has lost at least 86 species/16 subspecies of vertebrates. Among the extinct forms 3 species are mammals, 79 species/16 subspecies are birds, 3 species are reptiles, and 1 species is a freshwater fish. Another 10 species are possibly extinct, and 2 species are currently extinct in the wild.
In addition, there are 231 species/42 subspecies currently threatened with extinction (that is to say, either Critically Endangered, Endangered, or Vulnerable according to the IUCN Red List, as well as certain forms either listed as Data Deficient or Not Assessed but which are clearly at some risk of extinction). Of these, 13 species/9 subspecies are mammals, 157 species/32 subspecies are birds, 25 species/1 subspecies are reptiles, 3 species are amphibians, and 33 species are freshwater fishes.