Aldabra Atoll, Seychelles Located in the Indian Ocean, the Aldabra Atoll is an outstanding example of a raised coral atoll. Due to its remoteness and inaccessibility, the atoll has remained largely untouched by humans for the majority of its existence. Aldabra is one of the largest atolls in the world, and contains one of the most important natural habitats for studying evolutionary and ecological processes. It is home to the largest giant tortoise population in the world. The richness and diversity of the ocean and landscapes result in an array of colours and formations that contribute to the atolls scenic and aesthetic appeal. The least-disturbed large island in the Indian Ocean, Aldabra is of outstanding scientific interest. It is the only place in the world where a reptile is the dominant herbivore; some 150,000 giant tortoises (more than on the Galápagos Islands) feed on tie grasses and shrubbery, including plants that have evolved to take advantage of tortoise grazing patterns. The tortoises are the last survivors of a life form once found on many Indian Ocean islands; slow-moving and vulnerable, the giant land tortoises on all other Indian Ocean islands have been driven to extinction by human exploitation, leaving Aldabra as their only remaining stronghold. Aldabra is a classic coral atoll which has been built up from the seabed. It consists of four main islands of coral limestone separated by narrow passes and enclosing a large shallow lagoon. Most of the land surface consists of ancient coral reef (about 125,000 years old) now raised above sea level, the rest being even older reef limestones. The lagoon contains many smaller islands and the entire atoll is surrounded by an outer reef. The terrestrial flora is exceptionally rich for a small coral island, with 273 species of flowering plant and fern. Much of the land is covered with dense Pemohis acidula thicket and other shrubs. There are 19 endemic species, a further 22 species are shared only with neighbouring islands. Many of these plants are considered to be threatened. Mangroves surround the lagoon, and inshore waters also support seagrass meadows.
Posted on: Sun, 14 Sep 2014 13:43:08 +0000
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