Environment and Geography

Location

The Mpala Research Centre is located in Laikipia District, central Kenya. The property (20,000 ha/48,000 acres) is situated northwest of Mt. Kenya, 50km north of the Equator, and 50km from Nanyuki town. Mpala is bounded on the east side by the Ewaso Ng'iro river, and the north by the Ewaso Narok river. (See Map).

Climate

Warm days and cool nights predominate, with very low humidity in the driest season (January-April), and moderate humidity at other times. The rainfall is weakly trimodal, with peaks in Apr-May, July-Aug, and Oct-Nov, and a distinct dry season in Jan-Feb. There is considerable year-to year variation in total rainfall and in the seasonal distribution of rainfall. The property spans an altitudinal and climatic gradient that is higher, wetter and cooler in the southwest (1850m, 530mm rainfall), and lower, drier and hotter in the northeast (1550m, 400mm).

Geology

The northern two-thirds of Mpala is underlain by dissected Archean terrain with thin dark red sandy loams (latosols). The southwestern one-third of the property is characterized by a 100m high phonolite lava flow. Soils developed on the flow consist of a catena of black clay vertisols with impeded drainage, with brown calcareous loams (chestnut soils) on the higher elevations and steeper slopes. Scattered throughout this terrain are granitic inselbergs or kopjes, with the largest, ‘Mukenya’ (1846m), at the center. Fifteen dams have been constructed on Mpala, and there are more that 250km of internal roads.

Biodiversity

An estimated 800 plant species occur on Mpala, and lists of those collected to date (by Drs. T. Young and R. Faden) are available here (PDF). The vegetation is characteristic of semi-arid African savannas, predominantly grassy savanna bushland, with patches of woodland and open grassland. Dominant trees include species in the genera Acacia (Mimosaceae), Euphorbia (Euphorbiaceae), Balanites (Balanitaceae), and Boscia (Capparaceae).

More than 2,000 cattle, camels and sheep are ranched on Mpala, but the region also hosts an intact savanna mammal community, including Kenya's second largest elephant population. Eighty five mammal species and at least 300 bird species can be found on Mpala, with lists available (mammals (PDF) and birds (PDF)). Elephant, eland, plains zebra, oryx and giraffe are seasonally abundant, depending on rainfall and forage availability. Waterbuck, impala, Grant's gazelle, Jackson's hartebeest and bushbuck are resident. Lions, leopards, cheetahs, spotted hyenas, black-backed jackals, aardwolfs and bat-eared foxes are regularly seen.

Profound changes in patterns of biodiversity occur along altitudinal and climatic gradients that extend from the Mt. Kenya and Aberdare highlands in the south (3500m, max. rainfall 1600mm) to the northern lowlands (1000m, mean rainfall 300mm). Mpala is situated sufficiently close to the center of this gradient that some of the fauna and flora that are characteristic of either the mesic or xeric end tend to co-occur there. Obvious examples are Grevy's and Plains zebras, and helmeted and vulturine guineafowl.