A review of late quaternary pollen studies in East, Central and Southern Africa

Abstract

Results of fossil pollen studies in Eastern, Central and Southern Africa covering the last 32,000 years are surveyed in this paper. This research, conducted between 1951 and 1985, was mostly concentrated in East and Southern Africa, but a number of pollen sequences from intervening sites provide some links between the data of these two regions. In all this immense region, of half the African continent, information from fossil pollen is available only from some 30 sites. In addition to problems with absolute dating, the interpretation of the results in terms of former vegetation poses difficult questions. While it is far too early to draw detailed maps of former vegetation some very general conclusions can be inferred from the data presented. At two sites in East Africa pollen evidence has been found for the existence of a warmer and more humid period from ca. 32,000 to 28,000 yr B.P., an episode known as the Kalambo Interstadial. During the period from ca. 28,000 to 20,000 yr B.P. the climate in East and Central Africa was fairly similar to that during the Holocene moist period. In Southern Africa during the same period palynologic and geologic results indicate that cold episodes occurred while higher rainfall in East Africa, the Kalahari and adjacent regions caused high lake levels. During the last glacial maximum from ca. 20,000 to 16,000–14,000 yr B.P. aridity spread over nearly the whole region. The Zaire rain forest was considerably reduced and the tree line on the East African mountains was depressed by 900–1100 m, indicating a drop in mean temperature of 5–8°C. Lakes in East Africa and the Kalahari dried out, except for the southern Kalahari, its surroundings, and the SW Cape, where humidity was high. The general causes for aridity were the low evaporation at the ocean surface and the strong upwelling of colder waters. More humid conditions which have been postulated for the central part of southern AFrica could have been the result of lower evaporation in lake basins while the penetration of winter rainfall in the area has also been proposed. An abrupt change to warmer and more humid conditions in East Africa at ca. 12,000 yr B.P. reversed all the former processes. Rainfall also penetrated the Kalahari from the NW, NE and SW sides. Remarkable fluctuations in climate at this juncture could be demonstrated by pollen evidence in South Africa only at Aliwal North. During the Holocene, humid conditions persisted in East Africa until ca. 4000 yr B.P., when the climate became drier. Insufficient dated evidence in southern Africa makes it difficult to compare the various climate chronologies. In general the climate may have been wetter until about 4000 B.P. when a dry interval occurred. In East Africa pollen data point to deforestation by man during the last two millennia.