The Site comprises a 130-kilometre stretch of the Nosivolo River and almost 3,600 square kilometres of its river basin system. It includes a mosaic of flowing rivers, inland islets, lakes and marshes, vestiges of dense rainforests, highly fragmented gallery forests, secondary vegetation (savoka) covering cleared forest, and irrigated farm land. The near-natural ecosystem has the highest concentration of endemic freshwater fish species in Madagascar: it is home to 19 endemic fish species including the endangered Oxylapia polli. There are also six species of endemic birds: Madagascar rail (Rallus madagascariensis), Madagascar snipe (Gallinago macrodactyla), Madagascar sparrowhawk (Accipiter madagascariensis), rufous-headed ground roller (Atelornis crossleyi), Madagascan yellowbrow (Crossleyia xanthophrys) and Pollen’s vanga (Xenopirostris polleni); ten species of lemurs; reptiles; and ten endemic plant species. Among other resources, the Site provides materials for handicraft production, as well as fish, rice and a unique range of medicinal plants. Threats within the Site include habitat destruction from rice cultivation, gold and precious stones mining, and poaching for local consumption. These activities cause water pollution and disruption of riverbeds.