Seychelles consists of 115 islands spread across 1.4 million square kilometers of Indian Ocean, located approximately 1,500 kilometers east of Kenya and northeast of Madagascar. The archipelago divides into two distinct geological categories: the Inner Islands are granitic formations that represent fragments of the supercontinent Gondwana, making them some of the oldest mid-ocean islands on Earth at approximately 750 million years old, while the Outer Islands are low-lying coralline atolls and reef islands. Only 33 islands have ever been permanently inhabited. Mahé, the largest island at 154 square kilometers, holds 90 percent of the nation's population of approximately 100,000 people. Praslin covers 38 square kilometers, and La Digue spans 10 square kilometers. The remaining inhabited islands support small resort operations or conservation stations.
The granitic islands produce topography that does not exist elsewhere in island contexts. Mahé rises to 905 meters at Morne Seychellois, creating a mountain landscape where tropical forest grows on granite slopes. Silhouette Island reaches 740 meters at Mont Dauban. These elevations generate orographic rainfall that sustains vegetation communities unrelated to the typical low-elevation flora of oceanic islands. Beaches on the granitic islands feature massive granite boulders polished by wave action over millions of years, creating coastal formations that appear in no other archipelago. Anse Source d'Argent on La Digue displays the most photographed example, where rose-tinted granite forms emerge from turquoise water and white sand derived from coral rather than continental quartz.
Vallée de Mai on Praslin preserves the last substantial forest of coco de mer palms in natural conditions. This UNESCO World Heritage Site protects approximately 4,000 coco de mer trees within 19.5 hectares of endemic palm forest. The coco de mer produces the largest seed in the plant kingdom, with individual nuts weighing up to 25 kilograms and requiring six to seven years to mature. The species exists naturally only on Praslin and Curieuse Island. Female trees begin producing nuts at 20 to 40 years of age and continue for another 40 years. A mature nut sold legally through government channels costs 300 to 500 euros with export permits. The forest canopy reaches 30 meters, dense enough that GPS signals fail in the interior. Five other palm species endemic to Seychelles grow in this forest, including the thief palm, latanier millepattes, and palmiste. The endemic Seychelles black parrot, the only bird species found exclusively on Praslin, nests in dead coco de mer palms.
Aldabra Atoll in the Outer Islands represents the world's second-largest raised coral atoll at approximately 34 kilometers long and 14.5 kilometers wide. The atoll supports the largest population of giant tortoises on Earth, with roughly 100,000 individuals of the Aldabra giant tortoise species. These tortoises reach weights exceeding 250 kilograms and documented ages beyond 150 years. Aldabra lies 1,100 kilometers southwest of Mahé, accessible only by chartered boat requiring three to four days of ocean transit or by military or research aircraft. No permanent human population exists on the atoll. The Seychelles Islands Foundation manages access through research permits only. The lagoon covers 224 square kilometers and drains almost completely at low tide, exposing seagrass beds that feed the tortoises and green turtles. Aldabra remains one of the few places where ecosystem function approximates pre-human conditions because it was never subjected to plantation agriculture or significant introduced species.
Seychelles holds the highest proportion of endemic species per unit area of any country. Of 250 flowering plant species recorded in the archipelago, 80 exist nowhere else. Six endemic palm species grow here. Seychelles supports 12 endemic bird species, including the Seychelles magpie-robin, which numbered 12 individuals in 1965 and now exceeds 200 following translocation programs. The Seychelles warbler existed as a single population of 26 birds on Cousin Island in 1968; coordinated conservation programs have raised numbers above 3,000 across five islands. The jellyfish tree, reduced to a single specimen by 1970, now numbers several hundred individuals through propagation programs, though it remains one of the rarest plants on Earth. No terrestrial mammals evolved here naturally. The Seychelles sheath-tailed bat and Seychelles fruit bat represent the only native mammals, both endemic.