Biodiversity in the Inner Islands

Mahe Island

Mahe is the largest granitic island and holds the country’s capital city, commercial ports and administrative and financial center of Seychelles.

Biodiversity is contained within the Morne Seychellois National Park. Forest types on Mahe have been classified according to altitude and species composition. The low-land coastal forests extent from mangrove swamps towards the lower 50 meters. The intermediate forests are dominated by secondary vegetation while the higher misty peaks are collectively defined as mist forests. The climatic conditions at the summit of intermediate hills, along with the type of plants growing there are typical of ‘Inselberg’ type forest. To survive, plants have to adapt to dry, hot, windy and humid conditions. The Pitcher plants, the pandanus ‘Vacoa Montagne’, the Jelly fish tree are all examples of adaptations.

On Mahe most of the habitats occupied by the rarer vertebrates are confined within the Morne Seychellois National Park (MSNP). The MSNP, named after the highest peak (Morne Seychellois; 906 metres above sea level), was declared in 1979 as a result of the high abundance and diversity of native and endemic flora and fauna. It occupies nearly 5% of the total land surface area and spread over 3000 hectares (10 kilometres long and 2-4 km wide) of prime tropical mist forest. The humid tropical climatic conditions experienced especially at higher elevations create the perfect atmosphere for the MSNP to be described as tropical moist/mist forest. Variations in topography, soil, exposure, drainage, and within the last two centuries, logging, clearing, invasive alien species, forest fire, cultivation and secondary successions, have resulted in a mosaic of diverse plant communities.

Significant areas of the MSNP, especially at higher altitudes, are left in their natural state, where original forest persists. Most natural habitats contain important localised distributions of endemic flora and fauna which have evolved over the centuries in complete isolation. Almost all of the 76 extant endemic plant species (9% of total flora) including 5 palms, 6 pandanus, orchids and a pitcher plant are represented in the MSNP. Species such as the Seychelles Scops Owl and Jelly fish tree can only be found within the Park.

Silhouette Island

Silhouette Island is the Aldabra of the granitic Seychelles.

Silhouette is the third largest island in the archipelago.  The island has the second highest mountain reaching as high as 750 meters above sea level which allows it to have a wide range of ecosystems i.e. from coastal sand dune to high altitude mist forests. The only other island with a similar wide range of ecosystems is Mahe, which rises to 910 meters.  Both granitic islands host an exceptional biodiversity with many unique species of plant and animal found nowhere else in the world.  Although, it does not have flagship species such as the Coco de Mer and the giant tortoise, Silhouette Island has much more remnants of the ancient vegetation and ecosystems as Mahe. The reason for this, is that it is much more difficult to utilize the island for agricultural and forestry activities because of its difficult terrain. Unfortunately, on Mahe this was not the case and most of its original vegetation has been replaced with alien invasive species and agricultural crops such as cinnamon. For many scientists, Silhouette is considered to be the Aldabra of the granitics because of its unique flora and fauna, many of which can only be found on Silhouette alone. The international community recognizes the significance and contribution of Silhouette Island to the wealth of the global taxonomy and biodiversity.

Silhouette supports all amphibian species in Seychelles, the Palm frog has only been found on Silhouette. The Island was declared a National Park in 2010 by the President in recognition of its significant contributions towards making Seychelles the biodiversity hotspot of the Indian Ocean. This Designation was Seychelles contribution to world efforts to save the diversity of life on planet Earth and to increase the percentage of National Protected Areas to the golden target of 50%.  The declaration of Silhouette Island as a National Park is timely because the United Nations has declared 2010 the International year of Biodiversity to highlight the global environment crisis created partly by the continuous loss of biodiversity and increasing extinction of species worldwide.

Above all Seychelles had shown to the world that it is committed to protect the habitats of endemic plants and animals and the environment that provides the necessary services for us all to survive on this planet.

Praslin Island

The vallée de Mai is the most famous site for watching Seychelles Black parrots although they can be seen more easily elsewhere on the island. Tenrecs are frequently seen in the Vallée de Mai and this is the only site where the giant bronze gecko can easily be found; the Vallée de Mai is the best place to compare all three species of Bronze gecko.

Curieuse Island

Curieuse Island is situated just over 1km off the coast of Praslin and it is the fifth largest island of the inner granitic Seychelles. Some of the most important ecological areas on the island are the Turtle nesting beaches (accounting for more than 9% of all the nesting in the inner island), the Mangrove forest (supporting six of the seven native mangrove species known in Seychelles) and the Coco-de-Mer palm forests (one of the only two islands where the species grows in the wild). The island also house’s the largest free roaming giant land tortoises (some 300 individuals) in the inner granitic and supports a high number of endemic and threatened plant species such as Lalyann dile (Secamone schimperiana), Bwa bannann (Gastonia sechellarum), Bwa-d-Nat (Mimusops seychellarum), Palmist (Deckenia nobilis). Curieuse Island supports an interesting number of important species of plants and animals. Apart from the Vallée de Mai on Praslin, Curieuse is the only other place in the world where the Coco-de-Mer palm grows in a natural state. The woodlands also support a variety of animal life including endemic birds such as blue pigeon, black parrots and cave Swiftlet and reptiles such as the endemic green gecko, the Aldabran giant land tortoise, Seychelles skink. The endangered black parrot occurs only on Praslin and Curieuse. Three endemic avian species and 14 non-native land bird and two species of sea birds are recorded from Curieuse.

The Curieuse Island supports a rich endemic flora.  The population of several species of endemic plants are important for the conservation of the endemic invertebrates found on the island.  The much eroded red soil of the dry forest on the central hill of the island supports sparse shrubs and palms, rich in endemic species e.g. the Coco de Mer or double coconut (Lodoicea maldivica) which is found on the rocky slope of the island.  Richer endemic species such as Lalyann dile (Secamore schimperiana) found naturally only on Curieuse grows in the immediate forest, between the lowland forest and the summit.  At the summit of the island the endemic plants tends to be more specialised.  This is due to the widespread erosion, decrease fertility of the soil and intensification of the adverse effect of drought.  Endemic plants species can easily become endangered or extinct because they are restricted to certain habitats and are thus vulnerable.  With its large number of endemic flora, Curieuse also supports a number of endemic invertebrates which can be observed on certain plant species.

The extent of wetland areas on Curieuse Island’ coastal lowlands which are largely influenced by the marine environment are significant and comparative to localities elsewhere in granitic Seychelles.  There are at least two freshwater wetlands, one at the Doctor’s house, at the eastern end of the old leprosarium plateau and one on the west, at the end of the leprosarium plateau.  Plus, there are five permanent freshwater streams.  Species of insects (Odonata) have been observed around the freshwater pool at the Doctor’s House, which includes several species of water beetle, water bugs (Gerridae and Veliidae).  Insects from the family Gerridae, Veliidae and Agrionidae which include cicada, aphids, leafhoppers, landhoppers, etc… are found around fresh water marshes.  The ruddy turnstone (Arenaria inferpres), whimbrel (Nuttlenius phaeopu), and the endemic moorhen use the mangrove habitats.

The Curieuse Marine National Park, more especially the Curieuse Island and old turtle pond lagoon, is made up of an extensive composition of wetland. This wetland site has been legally protected under the National Parks and Nature Conservation Act.  It functions as fisheries habitat, protecting other important or endemic aquatic faunas such as crustacean, bivalves, fish and birds.

The mangrove ecosystem on Curieuse provides an important habitat for many species of animals. At the same time it hosts important mangrove species and subspecies which include Mangliye Rouz (Rhizophora mucronata), Mangliye Lat  (Bruiguiera gymnorhgiza), Mangliye Fler (Sonneratia alba), Mangliye Blan (Avicennia marina), Mangliye pti Fey (Lumnitzera racemosa), Mangliye Pasyans (Xylocarpus granatum), Mangliye Ponm (Xylocarpus molluccensis), Mangliye Zonn/Zerof (Ceriops tagal).  This ecosystem is one of the most diverse and pristine within the inner islands.  It acts as water storage for flood water and storm runoff, surface and groundwater protection and erosion control through soil stabilisation.  The mangrove is also important ecosystem for the juvenile coral reef fish where the habitat offers protection from other bigger organism, allowing them to feed and grow bigger before swimming out onto the coral reefs for our well-being.

The endangered Hawksbill and Green turtles are recorded breeding in large numbers.  All turtles emerging onto the beach of Curieuse are legally protected since 1979 when it became a Marine National Park.  However, poaching was still significant until the mid 1990s.  The Hawksbill nesting population is especially important on Curieuse.  A long-term marine turtle monitoring programme has been ongoing on Curieuse since 1981 (Mortimer, 2004).  From these monitoring it has been observed that the nesting population of Hawksbill turtle is increasing on Curieuse whilst that of Green turtle is thought to be either stable, or decreasing (Mortimer, 2004).  The biggest threat to the nesting populations has been identified as coastal erosion (Mortimer, 2004). The most suitable beaches for nesting have been identified to be Anse Papaie, Grand Anse and Anse Ste. Jose (Mortimer, 2004).  Actually, Mortimer (2004) states that on Curieuse island at least 2 beaches and possible a third one should be assigned the highest category of protection.  These beaches are Grande Anse, Anse Papaie and Anse Mandarin.  The designation is warranted because these three beaches account for 87% of all nesting that occurs on Curieuse; Grande Anse 60%, Anse Papaie (20%) and A. Mandarin (7%).

Curieuse is host to the second largest wild population of giant tortoises in the Seychelles, after the Aldabra World Heritage Site. Seychelles Giant Land Tortoise (Aldabrachelys gigantea), are found all over the island and latest population estimates revealed around 300 individuals that use the whole island for foraging and nesting.   They can be found in uphill habitats, shrubs, mangrove swamps and coastal dunes.  These exceptional creatures were once common on several Indian Ocean Islands but with the dramatic decline of these species, in the late 1800s it was declared endangered, one of the first species to have ever been designated as such.  In 1978 in an attempt to protect this special creature from the fate of extinction, 95 individuals were brought from Aldabra to Curieuse to preserve their numbers in a natural, wild environment, and to provide an opportunity to study this unique species.  Since their arrival on the island the number of tortoise has greatly increased.  The tortoises are one of the most important attractions which bring visitors to the island of Curieuse. Curieuse also has a tortoise nursery where visitors can see actual live tortoises at different stages as soon as they are hatched.  There is also a tortoise adoption programme where the funds collected goes towards conservation of the animals.

La Digue Island

The remaining fragments of woodland on La Digue are the only place to see the Seychelles Black paradice flycatcher in their natural habitats. As a result of constant pressure from habitat lost, some individuals were translocated to Denis Island during 2008. Sightings of individuals have been on Felicite Island. There are now two viable populations on two islands. Species diversity of the Island are relatively poor but some enigmatic flagship species like the ‘Vev’ and fresh-water Terrapins are easily encountered. Tree frogs are also occasionally found around the edge of the marsh.

Aride and Cousin Islands

Two Special Reserves that harbors important seabirds and endemic terrestrial avian fauna within the granitic Seychelles. These are the best islands for bird watching. Aride offers the best spectacle and has the highest diversity of sea birds in the granitic islands. Aride is also to be recommended for its abundance of skinks and geckos and the ease of viewing the Seychelles Magpie Robin, Seychelles Fody and Seychelles Warbler. Aride is also the only place in the granitic where Red-tailed tropic-birds nest as well as a relatively large colony of Roseate Tern.

Bird Island

Bird is a small coralline island dominated by its huge sooty tern colony. Over a million pairs of terns nest on the island which is also an exceptional spot for migrant birds and nesting turtles.

Fregate Island

Fregate is notable for supporting the largest population of Seychelles Magpie Robin and a thriving population of Seychelles White-eyes. The wetlands are restored and provide important habitats for endemic terrapins.

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