. The Conservation Atlas of Tropical Forests: Africa. History of Forests and Climate temperatures. Positive water balances on the continent would have been encouraged by the still depressed temperatures. The time around 1 1,000 BP is very significant at Muchoya, where a series of radiocarbon studies firmly dates a major change in vegetation, with replacement of Hagenia forest by moist lower montane forest. A similar drastic alteration in vegetation occurred at Ahakagyezi, but is less exactly dated. A rather sudden tempera- ture rise of 3°C is postulated as the main cause of these events. Evide
. The Conservation Atlas of Tropical Forests: Africa. History of Forests and Climate temperatures. Positive water balances on the continent would have been encouraged by the still depressed temperatures. The time around 1 1,000 BP is very significant at Muchoya, where a series of radiocarbon studies firmly dates a major change in vegetation, with replacement of Hagenia forest by moist lower montane forest. A similar drastic alteration in vegetation occurred at Ahakagyezi, but is less exactly dated. A rather sudden tempera- ture rise of 3°C is postulated as the main cause of these events. Evidence from elsewhere in Africa provides further suppon for this temperature increase; for example, this was the time of final deglaciation of Mt Elgon (Hamilton and Perrott, 1978). Perhaps as a result of higher evaporation under increased temperatures, there is some evidence for drier conditions in East Africa for some centuries after 11,000 BP. There was a major reduction in the level of Lake Kivu between 11,000 and 10,000 BP (Hecky and Degens, 1973) and Lake Victoria was reduced in level bnefly at around 10,000 BP (Kendall, 1969). Lake Victoria sediments contain reduced quantities of forest pollen at this time, another indication of climatic dryness (Kendall, 1969). It is intriguing that the major rise in temperature recorded at 11,000 BP in central Africa corresponds to a major decline in tem- peratures in north-west Europe. Earlier, after the end of the last ice age, temperatures had risen in Britain to values as high as the present, but between about 11,000 and 10,000 BP, severe weather returned, with formation and advance of a new ice-sheet in Scotland and with the limit of winter sea-ice in the North Atlantic moving as far south as the latitude of Spain (Lowe and Walker, 1984). The explanation for this apparent contradiction appears to lie in patterns of continental ice melt and melt-water flow in North America, probably responding to a major overall increase in global te
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