Flora
The park's predominant environment is open grass plain with scattered Acacia bushes. The western uplands of the park have highland dry forest with stands of Olea africana, Croton dichogamus, Brachylaena hutchinsii, and Calodendrum. The lower slopes of these areas are grassland. Themeda, Cypress, Digitaria, and Cynodon species are found in these grassland areas. There are also scattered yellow-barked Acacia xanthophloea. There is a riverine forest along the permanent river in the south of the park. There are areas of broken bush and deep rocky valleys and gorges within the park. The species in the valleys are predominantly Acacia and Euphorbia candelabrum. Other tree species include Apodytes dimidiata, Canthium schimperiana, Elaeodendron buchananii, Ficus eriocarpa, Aspilia mossambicensis, Rhus natalensis, and Newtonia species. Several plants that grow on the rocky hillsides are unique to the Nairobi area. These species include Euphorbia brevitorta, Drimia calcarata, and Murdannia clarkeana.
Fauna
A giraffe in Nairobi National Park.
The park has a large and diverse wildlife population. Species found in the park include African buffalo, baboon, black rhinoceros, Burchell's zebra, cheetah, Coke's hartebeest, Grant's gazelle, hippopotamus, leopard, lion, Thomson's gazelle,eland, impala, Masai giraffe, ostrich, vulture, and waterbuck.
Herbivores, including wildebeest and zebra, use the Kitengela conservation area and migration corridor to the south of the park to reach the Athi-Kapiti plains. They disperse over the plains in the wet season and return to the park in the dry season.The concentration of wildlife in the park is greatest in the dry season, when areas outside the park have dried up. Small dams built along the Mbagathi River give the park more water resources than these outside areas. They attract water dependent herbivores during the dry season
