Granitic Seychelles

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Granitic Seychelles
Granitic Seychelles forests
La Chauve Souris off Praslin.JPG
The small granitic island of Chauve Souris (Praslin)
Seychelles Inner Islands.png
Map of the Granitic Seychelles
Ecology
Realm Afrotropical
Biome Tropical and subtropical moist broadleaf forests
Geography
Area166 km2 (64 sq mi)
Countries Seychelles
Coordinates 4°30′58″S55°34′37″E / 4.516°S 55.577°E / -4.516; 55.577
Conservation
Conservation status Critical/endangered
Protected38 km2 (23%) [1]

The Granitic Seychelles are the islands in Seychelles which lie in central position on the Seychelles Bank and are composed of granite rock. They make up the majority of the Inner Islands, which in addition include the coral islands along of the rim of the Seychelles Bank, namely Bird Island and Denis Island. The Granitic Seychelles contrast with the Coralline Seychelles or the Outer Islands, several island groups made up of low coral islands with dry, infertile soils. [2] [3] [4]

Contents

The Granitic Seychelles are home to tropical moist forests, with several endemic species, including the coco de mer (Lodoicea maldivica), and the jellyfish tree (Medusagyne oppositifolia). [5]

Geography

Mahé is the largest and tallest island in Seychelles, at 145 square km and up to 905 m elevation. There are 42 granitic islands, in descending order of size: Mahé, Praslin, Silhouette, La Digue, Curieuse, Félicité, Frégate, Ste. Anne, North, Cerf, Marianne, Grand Sœur, Thérèse, Aride, Conception, Petite Sœur, Cousin, Cousine, Long, Récif, Round (Praslin), Anonyme, Mamelles, Moyenne, Ile aux Vaches Marines, L'Islette, Beacon (Ile Sèche), Cachée, Cocos, Round (Mahé), L'Ilot Frégate, Booby, Chauve Souris (Mahé), Chauve Souris (Praslin), Ile La Fouche, Hodoul, L'Ilot, Rat, Souris, St. Pierre (Praslin), Zavé, Harrison Rocks (Grand Rocher).

The Granitic Seychelles are fragments of the ancient supercontinent of Gondwana, and have been separated from other continents for 75 million years. The Granitic Seychelles form the northernmost part of the submarine Mascarene Plateau. [5] There are mafic xenolith intrusions in the granite in some areas.

Climate

The archipelago is about 5 degrees south of the equator, and has a humid tropical climate with little seasonal variation in temperature. Average annual rainfall varies with elevation, and exposure, ranging from 2,300 to 5,000 mm. There are heavy monsoon rains in the summer (November to February). Trade winds blow steadily from the southeast during the cooler months. [5]

Flora

The native vegetation of these islands consisted of palm, pandanus screw pines, and hardwood forest with mossy, ferny, cloud forest at higher elevations. The flora shows links with both Madagascar to the south and the African mainland to the west. Having been so isolated the islands are rich in endemic plant life including palm trees such as the coco de mer. [5]

The Granitic Seychelles have a relatively low number of flowering plant species, but a high rate of endemism. Approximately 268 flowering plant species are native to the island, in 216 genera. 28% of the species are endemic, with at least 13 endemic genera, of which most are monospecific. [6] Endemic genera include Deckenia, Glionnetia, Lodoicea, Medusagyne, Nephrosperma, Northia, Paragenipa, Phoenicophorium, Protarum, Roscheria, Seychellea, Vateriopsis , and Xyroschoenus . [7] 35% of flowering plant species are endangered. [6]

Fauna

The unique lizard and reptile populations of the Seychelles include seven species of caecilian and the iconic giant tortoises, Aldabrachelys gigantea arnoldi on the Granitic Seychelles, and Dipsochelys dussumieri on Aldabra. There have been some extinctions but the remaining endemic birds of these islands include the Seychelles scops owl (Otus insularis) and the Seychelles paradise flycatcher (Terpsiphone corvina). [5]

Threats and preservation

200 years of human settlement has seen the removal of much of the ancient habitat (including planting of coconut, vanilla and cinnamon), and the introduction of damaging invasive species. The Vallée de Mai on Praslin is the largest example of natural palm forest and is a World Heritage Site. [8]

Related Research Articles

<span class="mw-page-title-main">Seychelles</span> African island country in the Indian Ocean

Seychelles, officially the Republic of Seychelles, is an island country and archipelagic state consisting of 155 islands in the Indian Ocean. Its capital and largest city, Victoria, is 1,500 kilometres east of mainland Africa. Nearby island countries and territories include the Comoros, Madagascar, Mauritius, and the French overseas departments of Mayotte and Réunion to the south; and Maldives and the Chagos Archipelago to the east. Seychelles is the smallest country in Africa as well as the least populated sovereign African country, with an estimated population of 100,600 in 2022.

<span class="mw-page-title-main">Geography of Seychelles</span> Geography of the Seychelles islands

Seychelles is a small island country east of the African continent's mainland located in the Sea of Zanj due north of Madagascar, with Antsiranana as its nearest foreign city. Seychelles lies between approximately 4ºS and 10ºS and 46ºE and 54ºE. The nation is an archipelago of 155 tropical islands, some granite and some coral. the majority of which are small and uninhabited. The landmass is only 452 km2 (175 sq mi), but the islands are spread wide over an exclusive economic zone of 1,336,559 km2 (516,048 sq mi). About 90 percent of the population of 100,000 live on Mahé, 9 percent on Praslin and La Digue. Around a third of the land area is the island of Mahé and a further third the atoll of Aldabra.

<i>Lodoicea</i> Genus of plant, Coco de Mer

Lodoicea, commonly known as the sea coconut, coco de mer, or double coconut, is a monotypic genus in the palm family. The sole species, Lodoicea maldivica, is endemic to the islands of Praslin and Curieuse in the Seychelles. It has the biggest seed in a plant. It formerly also was found on the small islets of St Pierre, Chauve-Souris, and Ile Ronde, all located near Praslin, but had become extinct there for a time until recently reintroduced.

<span class="mw-page-title-main">Mascarene Islands</span> Archipelago east of Madagascar

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.

<span class="mw-page-title-main">Praslin</span> Island in the Seychelles, Somali Sea

Praslin is the second largest island (38.5 km2) of the Inner Seychelles, lying 44 km (27 mi) northeast of Mahé. Praslin has a population of around 7,533 people and comprises two administrative districts: Baie Sainte Anne and Grand' Anse. The main settlements are the Baie Ste Anne, Anse Volbert and Grand' Anse.

Curieuse Island is a small granitic island 1.13 sq mi (2.9 km2) in the Seychelles close to the north coast of the island of Praslin. Curieuse is notable for its bare red earth intermingled with the unique coco de mer palms, one of the cultural icons of the Seychelles, only growing on the two neighboring islands.

<span class="mw-page-title-main">Vallée de Mai</span> Protected area

Vallée de Mai Nature Reserve is a nature park and UNESCO World Heritage Site on the island of Praslin, Seychelles. It consists of a well-preserved palm forest, flagship species made up of the island endemic coco de mer, as well as five other endemic palms.

<i>Medusagyne</i> Genus of trees

Medusagyne oppositifolia, the jellyfish tree, is a species of tree endemic to the island of Mahé, of the Seychelles. It is the only member of the genus Medusagyne of the tropical tree and shrub family Ochnaceae. The plant, thought to be extinct until a few individuals were found in the 1970s, gets its common name from the distinctive jellyfish-like shape of its dehisced fruit.

Lazare Picault was a French explorer known for his exploration of islands in the Seychelles. Although Arab, Portuguese and British sailors visited the Seychelles prior to Picault, he was the first to do any extensive exploration.

<span class="mw-page-title-main">Seychelles skink</span> Species of lizard

The Seychelles skink also known as the Mangouya, is a species of skink in the family Scincidae. It is endemic to the Seychelles.

<i>Phoenicophorium</i> Genus of palms

Phoenicophorium, the thief palm, is a monotypic genus of flowering plant in the family Arecaceae. The sole species is Phoenicophorium borsigianum.

<span class="mw-page-title-main">Wildlife of Seychelles</span>

The wildlife of Seychelles comprises the flora and fauna of the Seychelles islands off the eastern coast of Africa in the western Indian Ocean.

Articles related to Seychelles include:

<span class="mw-page-title-main">Tiger chameleon</span> Species of lizard

The tiger chameleon, also known as the Seychelles tiger chameleon, is the only species in the resurrected genus Archaius. Initially placed into Chamaeleo, it was for some time moved to the genus Calumma by some. It is an endangered species of chameleon, found only on the Seychelles islands of Mahé, Silhouette and Praslin.

Round is an island in Seychelles, lying less than a mile southeast of the island of Praslin tilted a little to the southeast of Praslin's easternmost Peninsula and 48 km north-east of the island of Mahe

Chauve Souris is an island in Seychelles, lying 400 m northeast of the island of Praslin. Another nearby island - Saint-Pierre Island is located immediately in the north. The island is a granite island covered with tropical forest. Fauna is limited to the likes of skinks, geckos and limited birdlife that chiefly use the island as a roost.

Chauve Souris is an island in Seychelles, lying 400 m west of Anse La Mouche on the island of Mahé. The island is a rocky granite island covered with tropical forest. There is also a Chauve Souris island near the northern coast of the island of Praslin.

<i>Afrolychas braueri</i> Species of scorpion from the Seychelles

Afrolychas braueri, commonly known as the Seychelles forest scorpion, is a species of scorpion in the family Buthidae. It is currently thought to survive only on Silhouette Island, Seychelles, although the species was historically found on two additional Seychellois islands. This scorpion lives in leaf litter in forests that are largely unaffected by invasive plant species. It is a small yellowish-brown scorpion with three prominent keels on the dorsal surface of its mesosoma, which distinguishes it from other scorpions. While not much is known about the Seychelles forest scorpion's ecology due to the paucity of sightings, it is known to rely solely on its venom to capture its prey and defend its young. Its venom is not dangerous to humans.

Seychellea sechellarum is a species of flowering plant in the family Rubiaceae. It is a shrub endemic to the Seychelles. It is the sole species in genus Seychellea.

References

  1. ↑ Eric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545; Supplemental material 2 table S1b.
  2. ↑ "Map of Ecoregions 2017". Resolve. Retrieved August 20, 2021.
  3. ↑ "Granitic Seychelles forests". Digital Observatory for Protected Areas. Retrieved August 20, 2021.
  4. ↑ "Granitic Seychelles forests". The Encyclopedia of Earth. Retrieved August 20, 2021.
  5. 1 2 3 4 5 "Granitic Seychelles forests". Terrestrial Ecoregions. World Wildlife Fund.
  6. 1 2 Sylvain G. Razafimandimbison, Kent Kainulainen, Bruno Senterre, Charles Morel, and Catarina Rydin (2020). Phylogenetic affinity of an enigmatic Rubiaceae from the Seychelles revealing a recent biogeographic link with Central Africa: gen. nov. Seychellea and trib. nov. Seychelleeae. Molecular Phylogenetics and Evolution, Volume 143, 2020, 106685. ISSN 1055-7903, https://doi.org/10.1016/j.ympev.2019.106685.
  7. ↑ World Checklist of Vascular Plants (WCVP). Checklist of endemic plants of Seychelles. Retrieved 11 November 2023.
  8. ↑ Martin, Emma and Burgess, Neil. Granitic Seychelles Forests. One Earth. Retrieved 11 November 2023.
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