Aldabra Island, a remote atoll in the Indian Ocean, is one of Earth’s last untouched natural paradises. Part of the Seychelles, this isolated atoll showcases nature’s enduring power and diverse life. Its seclusion has fostered unique ecosystems, making it a globally significant site for understanding natural processes. Aldabra offers a rare glimpse into a world largely undisturbed by human activity.
Geographical Uniqueness
Aldabra Atoll is one of the world’s largest raised coral atolls, measuring 34 kilometers long and up to 14.5 kilometers wide. It comprises four major coral islands—Grande Terre, Malabar, Picard, and Polymnie—that encircle a vast, shallow lagoon, creating diverse habitats. Its rugged topography, shaped by weathered limestone, features pits, fissures, raised lagoon sediments, coastal beaches, and sand dunes. Its remote location has shielded it from extensive human impact. This isolation, coupled with a scarcity of fresh water, has preserved its unique biodiversity.
Iconic Terrestrial Wildlife
Aldabra is known for its terrestrial wildlife, notably the Aldabra Giant Tortoise (Aldabrachelys gigantea), which has the world’s largest population, estimated at 100,000 to 152,000 individuals. These tortoises act as ecosystem engineers, with their grazing habits influencing vegetation structure and creating “tortoise turf.” Their activity patterns are linked to daily temperatures, showing high activity in mornings and late afternoons, with rest during the hottest parts of the day.
Beyond tortoises, Aldabra harbors other unique terrestrial species, including endemic birds and land crabs. The Aldabra rail (Dryolimnas cuvieri aldabranus) is the last flightless bird in the Indian Ocean, a remarkable example of iterative evolution. This carnivorous rail, found in mangroves and dense scrub, feeds on arthropods, snails, geckos, and skinks. Land crabs like the coconut crab (Birgus latro) also thrive, demonstrating adaptations for terrestrial life.
Thriving Marine Ecosystem
The waters surrounding Aldabra Atoll host a rich and diverse marine ecosystem, characterized by near-pristine coral reefs. These reefs support an outstanding diversity of fish, with 185 species recorded within just three square kilometers of reef. The healthy marine food web exhibits a high prevalence of apex predators, including large snappers, groupers, and sharks.
Larger marine animals like manta rays and green sea turtles also frequent Aldabra’s waters, with turtles nesting on the atoll’s beaches. The atoll’s 196-square-kilometer lagoon is home to over 25 coral species and more than 1,000 fish species. Mangrove forests lining the lagoon provide important breeding grounds for many fish species, including sharks, and offer safe areas for juvenile turtles.
Global Conservation Efforts
Aldabra Atoll’s ecological value led to its designation as a UNESCO World Heritage Site in 1982, recognizing its outstanding universal value as an oceanic island ecosystem where evolutionary processes remain active. This designation underscores the atoll’s role as a natural laboratory for scientific research and discovery. The Seychelles Islands Foundation (SIF) manages the atoll, implementing strict regulations to protect its fragile environment.
Conservation initiatives include long-term monitoring programs for marine and terrestrial ecosystems, assessing coral reef health, fish abundance, and sea level changes. Researchers study the giant tortoise population and control invasive alien species, such as feral goats and certain invasive bird species, which have been successfully removed. Access to Aldabra is carefully controlled, with tourism strictly limited to minimize human interference and maintain the atoll’s ecological integrity.