The variations in climate, landforms and altitude have resulted in several overlapping ecosystems and distinct habitats. Within Tanzania the area is important for retaining uncultivated lowland vegetation, for the arid and semi-arid plant communities below 1,300 m, for its abundant short grass grazing and for the water catchment highland forests. Scrub heath, montane long grasslands, high open moorland and the remains of dense evergreen montane forests cover the steep slopes. Highland trees include peacock flower Albizzia gummifera, yellowwood Podocarpus latifolia, Hagenia abyssinica and sweet olive Olea chrysophylla. There is an extensive stand of pure bamboo Arundinaria alpina on Oldeani Mountain and pencil cedar Juniperus procera on Makarut Mountain in the west. The upland woodlands containing red thorn Acacia lahai and gum acacia.
The crater floor is mainly open shortgrass plains with fresh and brackish water lakes, marshes, swamps and two patches of Acacia woodland: Lerai Forest, with co dominants yellow fever tree Acacia xanthophloea and Rauvolfia caffra; and Laiyanai Forest with pillar wood Cassipourea malosana, Albizzia gummifera, and Acacia lahai. The undulating plains to the west are grass-covered with occasional umbrella acacia Acacia tortilis and Commiphora africana trees, which become almost desert during periods of severe drought. Blackthorn Acacia mellifera and zebrawood Dalbergia melanoxylon dominate in the drier conditions beside Lake Eyasi. These extensive grasslands and bush are rich, relatively untouched by cultivation, and support very large animal populations.
