Tanzania, situated IN east Africa just south of the equator, is a country characterized by high environmental, ecosystem, and cultural diversity. Much of Tanzania is also characterized by low-lying plains extending in from the coastal area in addition to the low-lying island archipelagos dominated by the islands of Mafia, Pemba, and Zanzibar. Inland there is the Eastern Arc Mountain chain, which is formed from heavily metamorphosed pre-Cambrian basement rocks, periodically uplifted by faulting and weathering over millions of years.

The mountains rise to 8,350 ft. (2,600 m.) in altitude, although maximum altitudes of 2,200 to 2,500 m. are more typical and cover an area of 2,085 sq. mi. (5,400 sq. km.). Farther west there is a high plateau of gently undulating terrain commonly between 4,920 and 6,561 ft. (1,500 and 2,000 m.). To the north of Tanzania, the landscape is dominated by the quite recent (2 million years old) volcanic chain that includes Kilimanjaro and Mount Meru.

Rainfall patterns in Tanzania are associated with the passage of the Intertropical Convergence Zone (ITCZ), which migrates from approximately 10 degrees S during January to 10 degrees N during July. The southeast trade winds are driven by annual oscillation of the ITCZ, bringing monsoonal rainfall to the east of Tanzania. Wet and dry seasons are clearly defined: Northern Tanzania experiences a rainy season from March to May and from October to December, whereas southern areas have one long rainy season from November to May. The elevational gradient on the eastern slopes of the Eastern Arc Mountains is relatively steep, whereas the western sides are relatively gently sloping. It is estimated that forests and woodlands cover 45 percent of Tanzania. The widespread flora on mountain islands led to the view of a continent-wide, archipelago-like center termed Afromontane; however, the distinct flora of the Eastern Arc Mountains suggests that they are floristically different from other African mountains. The altitudi-nal distribution of forest types comprises three major vegetation categories: upper montane forest, upper montane herb and shrub, and montane forest. Much of the coastal area is characterized by a coastal forest ecosystem that has been fairly heavily degraded, and the central part of the country is dominated by savanna bordered to the west by the Eastern Arc Mountains; these make up one of the world's hot spots of biodiversity because of their great variety of plant and animal species and their unusually high number of endemic species.

Relatively few palaeoecological records have been generated from Tanzania, with those records that have been produced being largely associated with the Rift Valley lakes located in the west of the country— the Empaki Crater Lake and an interesting ice core from the permanent ice on Kilimanjaro. One record from the Eastern Arc Mountains indicates relatively little ecosystem change over the past 40,000 years; this is in marked contrast with those records from the lowland lakes, which show expansion of montane forest into present savannah environments under the cold dry climate of the last glacial period. The Holo-cene, similar to other places in East Africa, is marked by human effects from around 4,000 years ago, and particularly after around 2,000 years ago as the agricultural transformation took place. Superimposed on this era are numerous climate change events, such

Lions in Tanzania stay close to their water source. Lion attacks have increased in rural Tanzania, the increase mirroring the dramatic rise in population, which grew by nearly 50 percent between 1988 and 2002 and encroached on the lions' habitat.

as the shift to more arid condition centered around 4,000 years ago and detected as a rapid increase in dust from Mount Kilimanjaro. The complicated picture of human-induced effects within a background of changing climate is something to be explored by generating new records on environmental history in a much underresearched part of the world.

sEE ALso: Climate Change, Effects; Deforestation.

BIBLioGRAPHY. C. Mumbi, R. Marchant, H. Hooghiems-tra, and M. Wooller, "Late Quaternary Ecosystem Stability From an East African Biodiversity Hot Spot: The Eastern Arc Mountains of Tanzania," Quaternary Research (in press); L.G. Thompson, E. Mosley-Thompson, M.E. Davis, K.A. Henderson, H.H. Brecher, V.S. Zagorodnov, T.A. Mashiotta, P.N. Lin, V.N. Mikhalenko, D.R. Hardy, and J. Beer, "Kilimanjaro Ice Core Records: Evidence of Holocene

Climate Change in Tropical Africa," Science (298, 2002); A. Vincens, Y. Garcin, and G. Buchet, "Influence of Rainfall Seasonality on African Lowland Vegetation During the Late Quaternary: Pollen Evidence From Lake Masoko, Tanzania," Journal of Biogeography (2007).

Rob Marchant University of York

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