The site lies in the delta of the Casamance river in the south-western corner of the country. It lies to the south of the main river channel, close to the border with Guinea-Bissau, and c.50 km south-west of Ziguinchor. It is low-lying, with the highest areas in the eastern end of the park (maximum altitude 11 m above sea-level). The habitat consists of mangroves fringing tidal channels, seasonally bare saline mudflats, some wooded savanna and terrestrial forest, including the only remaining small area of Guinea–Congo forest in the country. The mangrove areas show a zonation from the water’s edge, with first Rhizophora racemosa, then R. mangle with Paspalum vaginatum, then Avicennia africana with R. mangle, and Scirpus littoralis or other understorey species. The mudflats are colonized by Eleocharis mutata and E. geniculata. The Guinea–Congo forest occurs as islands within the Santiaba–Mandjak forest and includes species such as Parinari excelsa, Pithecellobium altissimum, Chlorophora regia, Detarium senegalense, and abundant Treculia africana forming the lower canopy.
See Box and Table 2 for key species. The site is the only IBA in Senegal in which two of the country’s globally threatened species, Ceratogymna elata and Illadopsis rufescens, are recorded. C. elata is said to occur as a small population seen regularly in the park and I. rufescens was caught in mist-nets twice in the 1970s and 1980s (one individual on each occasion). Circus macrourus has also been recorded at least once in the park. The wooded savanna and Guinea–Congo forest areas hold a number of species restricted to the Sudan–Guinea Savanna (A04) biome, including Nectarinia coccinigaster, recorded from no other IBA in Senegal. Nearly all of the species restricted to the Guinea–Congo Forests (A05) biome that are known to occur in the country are also recorded from the site. The site is said to be important for Palearctic migrant waders, but no numerical data are available.
Non-bird biodiversity: Over 50 mammal species have been recorded from this small area, including Piliocolobus badius temminckii (LR/nt) and Trichechus senegalensis (VU). The park hosts a variety of duikers (Cephalophus spp.) and Anomalurus beecrofti is found nowhere else in Senegal. Reptiles include Osteolaemus tetraspis (VU).
BirdLife International (2019) Important Bird Areas factsheet: Parc National de Basse Casamance. Downloaded from http://www.birdlife.org on 19/10/2019.