Aldabra Atoll

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Aldabra Atoll: A Unique Coral Atoll in the Indian Ocean

The Aldabra Atoll, located approximately 1,120 kilometers (700 miles) southwest of the capital city of Victoria on Mahé Island, is a remarkable natural wonder situated in the heart of the Indian Ocean. This coral atoll, which forms part of the Aldabra Group of islands within the Outer Islands of the Seychelles, was inscribed as a UNESCO World Heritage Site in 1982 due to its exceptional biodiversity and pristine condition, largely untouched by human influence.

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UNESCO Description of the World Heritage Site

The atoll is comprised of four large coral islands which enclose a shallow lagoon; the group of islands is itself surrounded by a coral reef. Due to difficulties of access and the atoll's isolation, Aldabra has been protected from human influence and thus retains some 152,000 giant tortoises, the world's largest population of this reptile.

UNESCO Justification of the World Heritage Site

Criterion (vii): Aldabra Atoll consists of four main islands of coral limestone separated by narrow passes and enclosing a large shallow lagoon, providing a superlative spectacle of natural phenomena. The lagoon contains many smaller islands and the entire atoll is surrounded by an outer fringing reef. Geomorphologic processes have produced a rugged topography, which supports a variety of habitats with a relatively rich biota for an oceanic island and a high degree of endemism. Marine habitats range from coral reefs to seagrass beds and mangrove mudflats with minimal human impact.

Criterion (ix): The property is an outstanding example of an oceanic island ecosystem in which evolutionary processes are active within a rich biota. Most of the land surface comprises ancient coral reef (~125,000 years old) which has been repeatedly raised above sea level. The size and morphological diversity of the atoll has permitted the development of a variety of discrete insular communities with a high incidence of endemicity among the constituent species. The top of the terrestrial food chain is, unusually, occupied by an herbivore: the giant tortoise. The tortoises feed on grasses and shrubbery, including plants which have evolved in response to its grazing patterns. The atoll's isolation has also allowed the evolution of endemic flora and fauna. Due to minimal human interference, these ecological processes can be clearly observed in their full complexity.

Criterion (x): Aldabra provides an outstanding natural laboratory for scientific research and discovery. The atoll constitutes a refuge for over 400 endemic species and subspecies (including vertebrates, invertebrates and plants). These include a population of over 100,000 Aldabra Giant Tortoise. The tortoises are the last survivors of a life form once found on other Indian Ocean islands and Aldabra is now their only remaining habitat. The tortoise population is the largest in the world and is entirely self-sustaining: all the elements of its intricate interrelationship with the natural environment are evident. There are also globally important breeding populations of endangered green turtles, and critically endangered hawksbill turtles are also present. The property is a significant natural habitat for birds, with two recorded endemic species (Aldabra Brush Warbler and Aldabra Drongo), and another eleven birds which have distinct subspecies, amongst which is the White-throated Rail, the last remaining flightless bird of the Western Indian Ocean. There are vast waterbird colonies including the second largest frigatebird colonies in the world and one of the world's only two oceanic flamingo populations. The pristine fringing reef system and coral habitat are in excellent health and distinguished by their intactness and the sheer abundance and size of species contained within them.

Encyclopedia Record: Aldabra

Aldabra, the world's second-largest coral atoll, is located east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 km (700 mi) southwest of the capital, Victoria on Mahé Island. Initially named by Arab seafarers for its harsh environment, Aldabra became a French colony dependency in the 18th century, leading to the exploitation of its natural resources, particularly giant tortoises. After passing through British hands, Aldabra faced potential military use in the 1960s, but international protests resulted in its protection. The atoll boasts unique geography, featuring the world's largest raised coral reef and a large shallow lagoon. Aldabra's history involves human impact, including failed agricultural ventures.

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IUCN World Heritage Outlook

The 2025 Conservation Outlook on Aldabra Atoll reports the following assessment:

Source: International Union for Conservation of Nature (IUCN) · View assessment