An Isolated Evolutionary Engine
Réunion is a geologic infant. It emerged from the Indian Ocean just over two million years ago, the product of a volcanic hotspot that remains highly active today. Isolation and dramatic topography make it a natural laboratory for evolution. The island has two volcanoes: the dormant Piton des Neiges, which rises to 3,070 meters, and the very active Piton de la Fournaise. This extreme vertical relief creates a vast range of microclimates, from humid subtropical rainforests on the windward eastern side to dry savannas on the leeward west.
This environmental variety, packed into an island of only 2,510 square kilometers, has driven rapid speciation. Plants and animals that arrived by chance—carried by wind, sea currents, or birds—found empty ecological niches and adapted over millennia. The result is a high degree of endemism, where species are found here and nowhere else. The island's core, covering over 100,000 hectares (about 42% of the island), is the Réunion National Park, a UNESCO World Heritage site recognized for its landscapes and biodiversity.
A Gallery of Endemics
The island's flora is unique. Of the 850 native plant species, 230 are endemic. These range from unique orchids and giant tree ferns (fanjans) to specialized vegetation clinging to recent lava flows. The high-altitude cloud forests, often misty, support mosses, lichens, and rare flowering plants like Heterochaenia fragrans, a plant in the bellflower family discovered in 2008.
Réunion's native fauna is dominated by birds, reptiles, and invertebrates. There are seven endemic land birds, including the Réunion cuckooshrike (Lalage newtoni), which is critically endangered, and the Réunion stonechat (Saxicola tectes). The island is also an important breeding ground for seabirds like Barau's Petrel (Pterodroma baraui), which nests exclusively on the high-altitude volcanic slopes.
The island's reptiles include several endemic gecko species. The Réunion Island ornate day gecko (Phelsuma inexpectata), a small, brightly colored lizard, is critically endangered and now occupies a tiny range of just 24 hectares along the southern coast. The insect life is diverse, with an estimated 5,000 species. Of the more than 3,300 terrestrial arthropod species already identified, 31% are endemic, and scientists estimate that over 60% of the island's arthropods are still waiting to be discovered.