| Society Islands tropical moist forests | |
|---|---|
 | |
 Map of the Society Islands | |
| Ecology | |
| Realm | Oceanian |
| Biome | tropical and subtropical moist broadleaf forests |
| Geography | |
| Area | 1,205 km2 (465 sq mi) |
| Country | French Polynesia |
| Administrative subdivisions | |
| Conservation | |
| Conservation status | Critical/endangered [1] |
| Protected | 41 km² (3%) [2] |
The Society Islands tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in the Society Islands of French Polynesia.
The Society Islands is a group of 14 islands, including nine high dormant volcanoes and five low coral atolls. They extend from 16º to 18º S latitude and from 148º to 154º W longitude. The islands comprise two groups, the Windward Islands (French: Îles du Vent) to the east and the Leeward Islands (French: Îles Sous-le-vent) to the west.[ citation needed ]
Tahiti in the Windward group is the largest of the Society Islands, with an area of 1,042 km2. The highest elevation in the islands (2,241 m) is also on Tahiti.[ citation needed ]
The islands were formed as the Pacific Plate moved slowly west-northwest over a volcanic hotspot. The islands increase in age from east to west. Mehetia at the eastern end of the chain is the youngest at less than 1 million years old, while Moorea is 1.5 million to 2 million years old. The western Leeward islands are at least 4.5 million years old, and have eroded and subsided to leave low coral atolls. The high islands' soils are mostly derived from basalt. Coralline limestone soils occur in coastal areas where ancient reefs were uplifted by geologic processes, and atoll soils are mostly of coral sand. [1]
The climate is humid and tropical. Average annual rainfall ranges from 1,700 mm near sea level to 8,000 mm or greater on windward mountain slopes. The summer months of December through February are the rainiest months, while March through November are typically cooler and drier. Easterly trade winds are consistent through much the year, and the eastern or windward sides of islands generally receive more rainfall. Mean annual temperature is 26º C. [1]
The natural vegetation is principally tropical rain forest, and includes lowland rain forests, montane rain forests, and cloud forests.
Lowland rain forest was once the most widespread forest type, but has been cleared from most of the coastal lowlands and is now found in valleys and on lower mountain slopes. Typical tree species include Inocarpus fagifer, Cananga odorata, Rhus taitensis, Pisonia umbellifera, Macaranga sp., Glochidion sp., Hibiscus tiliaceus , Tarenna sambucina , and the introduced Aleurites moluccana , along with the bamboo Schizostachyum glaucifolium . [1]
Montane rain forests occur above 300 m, and extend to higher elevations on the drier western slopes. The characteristic trees include Alphitonia zizyphoides, Hernandia moerenhoutiana, Metrosideros collina, Fagraea sp., Canthium spp., and Wikstroemia sp. [1]
Cloud forests occur between 400 and 1000 meters elevation, generally on the wetter eastern (windward) slopes. The easterly winds cool as they ascend the mountain slopes, and moisture condenses as rain and nearly continual cloud cover. Average annual temperatures are much cooler than in the lowlands, ranging from 14 to 18 °C. Pterophylla parviflora and Alstonia costata are the dominant tree species. Other common trees and shrubs include tree ferns ( Cyathea spp.) Fitchia spp., Myrsine spp., Fuchsia cyrtandroides , Sclerotheca spp., Cyrtandra spp., Metrosideros collina , Coprosma spp., and Psychotria spp. The trees are covered with epiphytic plants and lichens. The tree fern Angiopteris evecta on Moorea forms a canopy up to 9 meters wide. [1]
The islands are home to 623 native species of vascular plants, including 273 endemic species and one endemic genus. The trees Myrsine raiateensis and Pterophylla raiateensis are endemic to Raitaea. [3] The Raiatean endemics Sclerotheca raiateensis and Kadua raiateensis are considered endangered. [1]
The ancestors of the islands' native fauna arrived via long-distance dispersal from other islands, and evolved into distinct forms over millions of years.
BirdLife International designates the Society Islands as an endemic bird area based on the islands' five surviving endemic species and several extinct ones. Three species recorded on Captain Cook's 1773 visit, the Tahiti rail (Gallirallus pacificus) from Tahiti, the Tahitian sandpiper (Prosobonia leucoptera) from Moorea and Tahiti, and the Raiatea parakeet (Cyanoramphus ulietanus) from Raiatea are now extinct. Other extinct endemic species include the black-fronted parakeet (Cyanoramphus zealandicus) and Maupiti monarch (Pomarea pomarea). [4]
Endangered native species include an endemic subspecies of striated heron (Butorides striatus patruelis), the Society Islands pigeon (Ducula aurorae), Tahiti reed warbler (Acrocephalus caffer), Tahiti swiftlet (Aerodramus leucophaeus), and Tahiti monarch (Pomarea nigra). [1]
Land snails in the genera Partula and Samoana are part of the islands' unique biodiversity. From ancestors that are thought to have to have arrived in a single colonization event, the Partula land snails evolved into 53 distinct species. They were once found throughout the high islands. The native land snails on Tahiti and Moorea have been decimated by introduced predatory land snails Euglandina rosea and Gonaxis spp., and 15 species are now extinct or endangered. [1]
Humans have extensively altered the flora and fauna of the islands since the arrival of Polynesians 1000 to 2000 years ago. Polynesian settlers brought plants like the coconut palm (Cocos nucifera) and candlenut tree (Aleurites moluccana) which have naturalized across the archipelago, as well as pigs and the Polynesian rat (Rattus exulans). Europeans started visiting the islands in the 18th century and later conquered and settled there, and brought many more exotic plants and animals. [1]
The lowlands below 500 meters elevation have mostly been cleared of the native forests, and replaced with coconut plantations and other crops, or with anthropogenic grasslands maintained by frequently-set fires. [1]
Europeans brought black rats (Rattus rattus) and brown rats (R. norvegicus), which along with house cats have devastated the islands' native birds. Archeological sites have recovered remains of ten seabird species and 14 land birds which are no longer present on the islands. These include the extinct Huahine gull (Chroicocephalus utunui), two parrots ( Vini vidivici and V. sinotoi ), three pigeons, and the Raiatea starling ( Aplonis sp.), along with two species of Prosobonia sandpiper, three species of parrots, and one pigeon that have gone extinct since Europeans arrived. [1]
Relatively intact natural vegetation covers about 30% of the ecoregion. [2] Relatively intact but unprotected areas include lowland Inocarpus forest and the Oponohu lowland forest on Moorea, the Vallée de Vaiote on Tahiti, the Vallée d’Avera and montane forest on Raiatea, Manuae island, and seabird colonies on Tetiaroa, Fenuaura, Motuone, and Mopiihaa atolls. [1]
The greatest threat to the Society Islands' wild forests is the invasive tree Miconia calvescens . It was introduced in 1937 from South America, and has expanded to cover large areas of Tahiti and portions of Moorea and Raiatea. The trees form dense stands up to 15 meters high which shade out all but their own seedlings. The tree's seeds are dispersed by birds, and manual removal has been necessary to keep them from spreading to new areas and to smaller islands. [1]
A 2017 assessment found that 41 km², or 3%, of the ecoregion is in protected areas. [2] Protected areas include:
The Mascarene Islands or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of the islands belonging to the Republic of Mauritius as well as the French department of La Réunion. Their name derives from the Portuguese navigator Pedro Mascarenhas, who first visited them in April 1512. The islands share a common geologic origin in the volcanism of the Réunion hotspot beneath the Mascarene Plateau and form a distinct ecoregion with a unique flora and fauna.
The Vanuatu rain forests are tropical and subtropical moist broadleaf forests ecoregion which includes the islands of Vanuatu, as well as the Santa Cruz Islands group of the neighboring Solomon Islands. It is part of the Australasian realm, which includes neighboring New Caledonia and the Solomon Islands, as well as Australia, New Guinea, and New Zealand.
Moʻorea, also spelled Moorea, is a volcanic island in French Polynesia. It is one of the Windward Islands, a group that is part of the Society Islands, 17 kilometres (11 mi) northwest of Tahiti. The name comes from the Tahitian word Moʻoreʻa, meaning "yellow lizard": Moʻo = lizard ; Reʻa = yellow. An older name for the island is ʻAimeho, sometimes spelled ʻAimeo or ʻEimeo. Early Western colonists and voyagers also referred to Moʻorea as York Island or Santo Domingo.
Raiatea or Ra'iatea is the second largest of the Society Islands, after Tahiti, in French Polynesia. The island is widely regarded as the "centre" of the eastern islands in ancient Polynesia and it is likely that the organised migrations to the Hawaiian Islands, New Zealand and other parts of East Polynesia started at Raiatea.
The Madagascar subhumid forests are a tropical moist broadleaf forest ecoregion that covers most of the Central Highlands of the island of Madagascar. They are included in the WWF's Global 200 list of outstanding ecoregions. Most of the original habitats have been lost due to human pressure.
Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and elongated leaves, known as "laurophyll" or "lauroid". Plants from the laurel family (Lauraceae) may or may not be present, depending on the location.
The Hawaiian tropical rainforests are a tropical moist broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of 6,700 km2 (2,600 sq mi) in the windward lowlands and montane regions of the islands. Coastal mesic forests are found at elevations from sea level to 300 m (980 ft). Mixed mesic forests occur at elevations of 750 to 1,250 m, while wet forests are found from 1,250 to 1,700 m. Moist bogs and shrublands exist on montane plateaus and depressions. For the 28 million years of existence of the Hawaiian Islands, they have been isolated from the rest of the world by vast stretches of the Pacific Ocean, and this isolation has resulted in the evolution of an incredible diversity of endemic species, including fungi, mosses, snails, birds, and other wildlife. In the lush, moist forests high in the mountains, trees are draped with vines, orchids, ferns, and mosses. This ecoregion includes one of the world's wettest places, the slopes of Mount Waiʻaleʻale, which average 373 in (9,500 mm) of rainfall per year.
The grey-green fruit dove is a species of bird in the family Columbidae. It is endemic to the Society Islands in French Polynesia. Its natural habitat is subtropical or tropical moist lowland forests.
The Samoan tropical moist forests are a tropical moist broadleaf forest ecoregion in the Samoan Islands of the Pacific Ocean.
The Fiji tropical moist forests is a tropical moist forest ecoregion in Fiji and Wallis and Futuna. It covers the windward sides of Viti Levu and Vanua Levu, Fiji's largest islands, as well as the smaller Fijian islands and the three islands that make up Wallis and Futuna, an overseas territory of France.
The Tongan tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion that includes the Tonga archipelago and Niue.
The Cook Islands tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion that covers the Southern Cook Islands in the Cook Islands.
The Tubuai tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in French Polynesia. It covers the Austral Islands.
The Marquesas tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in the Marquesas Islands of French Polynesia.
The Tuamotu tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in the Tuamotu Archipelago of French Polynesia and the Pitcairn Islands.
The Western Polynesian tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in Polynesia. It includes Tuvalu, the Phoenix Islands in Kiribati, Tokelau, and Howland and Baker islands, which are possessions of the United States.
The Carolines tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion in Micronesia. It includes the central and eastern Caroline Islands in the Federated States of Micronesia.
The Yap tropical dry forests is a tropical and subtropical dry broadleaf forests ecoregion in Micronesia. It includes the Yap Islands and neighboring atolls in the Federated States of Micronesia.
Pterophylla parviflora, formerly known as Weinmannia parviflora, is a species of plant in the family Cunoniaceae. It is endemic to the Society Islands of French Polynesia.
Pterophylla vescoi, formerly known as Weinmannia vescoi, is a species of plant in the family Cunoniaceae. It is a tree native to the island of Raiatea and possibly Tahiti in the Society Islands of French Polynesia.
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