Mascarene Islands

The Mascarene Islands (; ) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of islands belonging to the Republic of Mauritius as well as the French department of Réunion. Their name derives from the Portuguese navigator Pedro Mascarenhas, who first visited them in April 1512. The islands share a common geological origin beneath the Mascarene Plateau known as the Mauritia microcontinent which was a Precambrian microcontinent situated between India and Madagascar until their separation about 70 million years ago. They form a distinct ecoregion with unique biodiversity and endemism of flora and fauna.

Geography

The archipelago comprises three large islands, Mauritius, Réunion, and Rodrigues, plus a number of volcanic remnants in the tropics of the southwestern Indian Ocean, generally between 700 and 1,500 kilometres east of Madagascar. The terrain includes a variety of reefs, atolls, and small islands. They present various topographical and edaphic regions. On the largest islands these gave rise to endemism and unusual biodiversity. The climate is oceanic and tropical.

Mauritius is located 900 km east of Madagascar. It has an area of 1,865 km2. The highest point is 828 meters above sea level. Mauritius is the most populous of the Mascarene Islands, with a population of 1,252,964.

Réunion is located 150 km southwest of Mauritius. It is the largest of the islands, with an area of 2,512 km2. Piton des Neiges (3,069 m), an extinct volcano, is the highest peak on Réunion and in the islands. Piton de la Fournaise is an active volcano on Réunion which erupts frequently. These Thirteen islands of St. Brandon on Permanent Grant are L'île du Sud (South Island, l'île Boisée), Petit Fou, l'Avocaire, l'île aux Fous, L'île du Gouvernement, Petit Mapou, Grand Mapou, La Baleine, L'Île Coco, Île Raphael, Verronge, l'île aux Bois and Baleines Rocks.

There are several submerged banks or shoals:

Saya de Malha Bank is a large, submerged bank. Prehistorically it was a group of volcanic islands and was enjoined to the Great Chagos Bank until continental drift pushed them apart.
Soudan Banks are a group of low-lying banks on the Mascarene Plateau.
Nazareth Bank is located just north of Cargados Carajos, and prehistorically they were a single geological feature. Today it is a large, shallow fishing bank.
Hawkins Bank is located on the northernmost point of the Mascarene Plateau.

Geology

thumb|left|[[Piton de la Fournaise]]

The islands are volcanic in origin; Saya de Malha (35 mya) was the first of the Mascarene islands to rise out of the Indian Ocean due to the Réunion hotspot, followed by Nazareth Bank (approximately 2 mya later), Soudan Bank and Cargados Carajos. The youngest islands to form were Mauritius (7–10 mya), the oldest of the existing islands, created along with the undersea Rodrigues ridge. The islands of Rodrigues and Réunion were created in the last two million years. Réunion is the largest of the islands (2,500 km2), followed by Mauritius (1,900 km2) and Rodrigues (110 km2). Eventually, Saya de Malha, Nazareth and Soudan were completely submerged, Cargados Carajos remaining as a coral atoll. The Réunion hotspot was beginning to cool and Rodrigues came out as a small island.

Réunion is home to the highest peaks in the Mascarenes, the shield volcanoes Piton des Neiges (3,069 m) and Piton de la Fournaise (2,525 m). Piton de la Fournaise, on the southeastern corner of Réunion, is one of the most active volcanoes in the world, erupting last in December 2021. Piton de la Petite Rivière Noire (828 m) is the highest peak on Mauritius, and the gentle hills of Rodrigues rise to only 390 m.

The Mascarene Plateau is an undersea plateau that extends approximately 2000 km, from the Seychelles to Réunion. The plateau covers an area of over 115,000 km2 of shallow water, with depths ranging from 8 to 150 meters, plunging to 4000 m to the abyssal plain at its edges. The southern part of the plateau, including the Saya de Malha Bank, Nazareth Bank, Soudan Banks and Cargados Carajos Shoals (Saint Brandon) (then one large island), was formed by the Réunion hotspot. These were once volcanic islands, much like Mauritius and Réunion, which have now sunk or eroded to below sea level or, in the case of the Cargados Carajos, to low coral islands. The Saya de Malha Bank formed 35 million years ago, and the Nazareth Bank and the Cargados Carajos shoals after that. Limestone banks found on the plateau are the remnants of coral reefs, indicating that the plateau was a succession of islands. Some of the banks may have been islands as recently as 18,000–6,000 years ago, when sea levels were as much as 130 meters lower during the most recent ice age.

History

thumb|left|upright|[[Pedro Mascarenhas, namesake of the Mascarene Islands, was Viceroy of Portuguese India.]]

thumb|1780 map of Reunion, Mauritius, and Rodrigues

The early colonial history of the islands, like that of the Caribbean, featured a succession of takeovers between rival powers: the Portuguese, Dutch, French and British all ruled some or all of the islands.

Around 1507, the explorer Diogo Fernandes Pereira discovered the island group. The area remained under nominal Portuguese rule until Étienne de Flacourt arrived with a French naval squadron and took possession in 1649. From 4 June 1735 to 23 March 1746, a single French Mascarene Islands chartered colony under one gouverneur général (governor general) contained Isle de France (now Mauritius), Île Bourbon (Réunion) and Séchelles (Seychelles). On 14 July 1767 this became a French crown colony, still under one governor general. From 3 February 1803 until 2 September 1810 the French colony of Indes-Orientales, under a capitaine général (captain-general), included Réunion and (nominally) the Seychelles.

Mauritius

alt=VOC - Logo of the Dutch East India Company|right|69x69px|Logo of the Dutch East India Company

It is postulated from navigational charts, such as the Cantino planisphere of 1502, that Arab sailors first discovered Mauritius around 975, calling it Dina Arobi (abandoned island). The earliest confirmed discovery on record was in 1507 by Portuguese sailors. alt=Isle de France (Mauritius)|right|80x80px|Isle de France (Mauritius) under the French

The Dutch took physical possession in 1598, establishing a succession of short-lived settlements over a period of about 120 years, before abandoning their efforts in 1710.

France took control in 1715, renaming it Isle de France. In 1810, the United Kingdom invaded the island to protect its East India ships coming around the Cape of Good Hope from French pirates. Four years later, at the Treaty of Paris, France ceded Mauritius and its dependencies to the United Kingdom.

Under British Mauritius (1810-1968), the island successfully developed as a sugar cane-based plantation economy and colony until independence in 1968.

Rodrigues

Rodrigues was first discovered by the Arabs but named after Portuguese navigator Diogo Rodrigues. It was under Dutch control in 1601 and settled by the French in 1691. Britain took possession of Rodrigues in 1809. When Mauritius gained independence in 1968, Rodrigues was forcefully joined to it. Rodrigues remains an autonomous region of Mauritius.

Réunion

Réunion was discovered first by the Arabs then by the Portuguese, who named it Santa Apolónia. It was then occupied by the French as part of Mauritius. It was first inhabited by French mutineers who arrived on the island between 1646 and 1669. It was given its current name in 1793. From 1810 to 1815 it was held by the British, before being returned to France. Réunion became an overseas department of France in 1946.

Climate

The climate of the islands is tropical. At low elevations summer temperatures (December to April) average 30 °C. Winter temperatures (May to November) are generally cooler, around 25 °C. Temperatures are cooler in the mountains, averaging 18 °C. During the winter short-lived snow can fall on Réunion's high peaks.

Southeasterly trade winds blow throughout the year. Rainfall is generally higher on the windward sides of the islands. On Mauritius average annual rainfall in the lowlands varies from 1905 mm on the windward southeast coast to 890 mm on the leeward side. Rainfall in the mountains is higher, varying from 2540 mm to 4445 mm annually. Tropical cyclones occur occasionally, bringing heavy rain and high winds, and causing erosion and landslides.

Coastal habitats include beach vegetation, coastal wetlands, and swamp forests, grading into lowland rain forest on the windward sides of the islands and lowland dry forests to leeward.

The dry lowland forests are found on the leeward sides of the islands, from sea level to 200 metres in areas with less than 1000 mm of average annual rainfall. Palms are the dominant trees, including species of Latania and Dictyosperma album, along with the palm-like screw-pines (Pandanus spp.).

The Mascarenes are home to many endemic species of Dombeyoideae, the monotypic genus Psiloxylon (Psiloxylon mauritianum), and members of the family Monimiaceae (the genera Monimia and Trochetia, and species of Tambourissa) and Escalloniaceae. Indigenous trees include species of the genera Ocotea, Erythrina, Sideroxylon, and Foetidia. Other endemic genera include Berenice, Heterochaenia, Nesocodon, Ruizia, and Astiria.

There are 24 species of trees and shrubs in the Mascarenes from subfamily Dombeyoideae, 23 of which are endemic to the islands. The Macarenes' endemic species are polyphyletic and split into nine clades. Trochetia appears monophyletic and more closely related to Eriolaena and Helmiopsis than to Dombeya. All Dombeya taxa are included in a clade together with Ruizia and Astiria, this means that Dombeya is paraphyletic. In terms of breeding systems the Malagasy Dombeyoideae are hermaphroditic, whereas those of the Mascarenes are considered dioecious. The polyphyly of the Mascarene Dombeyoideae suggests that dioecy has been acquired several times. At least five colonization events from Madagascar to the Mascarene archipelago occurred. The evolutionary history of two lineages of Mascarene Domeyoideae seems to be related to adaption to xeric habitats.

The flora of the islands co-evolved with the island's unique fauna over millions of years. The human-caused extinction of several of the Mascarenes' land animals, and the introduction of exotic animals to the islands by humans, has disrupted the reproduction and thriving of various island plants. For example, the Tambalacoque tree (Sideroxylon grandiflorum), often called the dodo tree, is not producing young trees and is threatened with extinction. The extinct dodo, Cylindraspis tortoises, and broad-billed parrots, along with fruit bats, played an important role in dispersing the seeds. Passing through the animals' digestive tract aided in the seeds' germination. However the trees' decline may be mostly due to introduced crab-eating macaques (Macaca fascicularis) destroying unripened seeds.

Contemporary sources state that the dodo used gizzard stones Seed distribution of at least some Ocotea species is performed by frugivorous birds and there exist a few reports of "solitaires" from the Mascarenes without mention of which island these came from, and the term was also used for other species with "solitary" habits, such as the Réunion blue swamphen and the Réunion sacred ibis. At one point it was even believed that Réunion was the home of not only a white dodo, but also a white solitaire. In 1786, sub-fossil bones were discovered in a cave which confirmed Leguat's descriptions, but at this time no living residents of Rodrigues remembered having seen living birds. The star constellation Turdus Solitarius was named after this bird.

Today 17 endemic bird species survive on the islands. Two species – the Mascarene paradise flycatcher (Terpsiphone bourbonnensis) and Mascarene swiftlet (Aerodramus francicus) – inhabit both Mauritius and Réunion. Eight species are endemic to Mauritius – the Mauritius grey white-eye, (Zosterops mauritianus), Mauritius cuckooshrike (Lalage typica), Mauritius kestrel (Falco punctatus), Mauritius fody (Foudia rubra), Mauritius bulbul (Hypsipetes olivaceus), Mauritius parakeet (Psittacula eques), Mauritius olive white-eye (Zosterops chloronothos), and pink pigeon (Nesoenas mayeri). The Réunion grey white-eye (Zosterops borbonicus), Réunion cuckooshrike (Lalage newtoni), Réunion stonechat (Saxicola tectes), Réunion olive white-eye (Zosterops olivaceus), and Réunion bulbul (Hypsipetes borbonicus) are endemic to Réunion. The Rodrigues warbler (Acrocephalus rodericanus) and Rodrigues fody (Foudia flavicans) are found only on Rodrigues.

The Grand River South East (34 km) is the longest river on Mauritius, followed by Rivière du Poste (23 km), Grand River North West (22 km), Rivière La Chaux (22 km), and Rivière des Créoles (20 km). Mauritius has two natural crater lakes, Grand Bassin and Bassin Blanc. to protect St. Brandon from pollution and to protect surviving flora and fauna in the Cargados Carajos.

Protected areas

Protected areas constitute 40.6% of the Mascarene Islands' land area. Terrestrial protected areas on Mauritius include Black River Gorges National Park, Bras d'Eau National Park, Perrier Nature Reserve, Corps de Garde Nature Reserve, Le Pouce Nature Reserve, Cabinet Nature Reserve, Gouly Pere Nature Reserve, and Bois Sec Nature Reserve. There are 32 designated protected areas on Réunion, including Réunion National Park (1055.15 km2), which cover 63.13% of the island.

References

Sources

Quammen, David, (1996) The Song of the Dodo. Touchstone, New York.
Diamond, Jared, (1984) "Historic extinctions: A rosetta stone for understanding prehistoric extinctions". In: P. Martin and R. Klein (eds.) (1984) Quaternary Extinctions: A prehistoric revolution. University of Arizona Press, Tucson.

External links

Scientific research application on the nature reserve of Mare-Longue (Réunion - Mascarene Islands)
Carta del Cantino, PDF from the site of Biblioteca Estense, Modena
del Cantino, Cantino planisphere image, zoomable to very high resolution, at Bibliothèque et Archives nationales du Québec. (Click on 1:1 button to get maximum resolution. Click on Image plein écran to get full-screen view.)