The Bijagós Archipelago, located off the coast of Guinea-Bissau, is defined by a dynamic relationship between the sea and the land. Twice daily, the movement of tides across 88 islands and islets dramatically alters the landscape, exposing vast mudflats and sandflats during low tide and submerging them as the water rises. In 2025, this unique environment was designated a UNESCO World Heritage site, recognizing it as the only active deltaic archipelago on Africa's Atlantic coast.
This rhythmic tidal cycle is a primary driver of the region's high productivity. The archipelago serves as a critical hub for the East Atlantic Flyway, providing feeding grounds for approximately 870,000 migratory shorebirds that forage on the exposed mudflats. As the tide rises, the ecosystem shifts; marine mammals such as dolphins and manatees, along with various fish species, navigate into the mangrove forests. Simultaneously, the sandy beaches become nesting grounds for significant populations of green sea turtles, particularly on the island of Poilão.
The survival of these sea turtles is precarious. Hatchlings face numerous predators on land and in the water, with estimates suggesting that fewer than 1 percent reach adulthood. Research published in 2025 highlights that the archipelago experiences tidal ranges reaching up to 7 meters (23 feet), significantly higher than the 1-meter range common elsewhere along the West African coast. Scientists attribute this phenomenon to the area's shallow shelf and specific estuarine geometry, findings validated through satellite altimetry data from NASA and CNES missions.
Source: NASA
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