Kahuzi-Biega National Park is subdivided into two areas connected by a narrow corridor: the mountain rain forest (or Afro-montane forest) on the one hand, and the lowland rain forest (Guineo-Congolese, relatively humid type) on the other hand. It is one of the few regions in Africa where the transition between these two rainforest types has remained largely intact.
So far, more than 1178 plant species have been recorded at high altitude, making it the third site of the Albertine Rift in terms of species richness, after the Virunga National Park in the DRC and the Bwindi Impenetrable Forest in Uganda. . On the other hand, the flora of low altitude remains little known.
The inventory of endemic species in Kahuzi-Biega National Park is far from complete, and we still discover many new species belonging mainly to the families of Balsaminaceae, Orchidaceae, Violaceae, Euphorbiaceae, Araliaceae, Anacardiaceae, and several others. families with a single determined species (Fischer, 1995).
The mountainous part of the Park is covered with essentially forest vegetation, within which there are other formations linked to particular edaphic conditions: hydromorphic, marshy, flooded soils, or lateritic crusts.
According to their physiognomy and their floristic composition, depending on the altitude, the forests of the PNKB are differentiated into flat floors (678-1250 m), sub-mountain (1250-1700 m), mountain (1700-2600 m) and afro -subalpine (2600-3308 m) (Mangambu et al.2013).
The protected plant cover of the Park has a regulating effect on the hydrological regime of the region. In particular, it ensures the protection of watersheds. In addition, the exceptional forest cover of the PNKB constitutes an important carbon sink contributing to the fight against climate change at the global level.