Saiwa is the smallest park in Kenya, only 3 square km. It was established to protect the semi-aquatic Sitatunga antelope and encloses the swamp fed by the Saiwa river together with its fringing belts of rain forest. The park is enclosed by subsistence farming settlements. Vegetation is a mixture of forest and swamp vegetation. The swamp is dominated by tall bullrushes and sedges. The swamp is bordered by a mixture of grassland, riverine forests and acacia.
Saiwa Swamp National Park