The Site includes the estuary of the River Kouilou and its sandy shores and sand banks, other permanent and temporary rivers, lakes, the Yombo lagoon, marshes including some dominated by Cyperus papyrus, and flooded and swamp forests including mangrove forests. Due to its diverse ecosystems and the permanent presence of water, the Site maintains populations of chimpanzees, sitatunga (Tragelaphus spekii), African buffalo and hippopotamus, and fish such as the slender lungfish (Protopterus dolloi) which is endemic to the Congo Basin and neighbouring river basins. Exploitation of parts of the Site such as the Monje mombomo river has long been forbidden, ensuring the stability of habitats and the maintenance of biological diversity. Silting at the mouth of the River Kouilou and Yombo lagoon constitutes a real threat to the Site.