VEGETATION AND CLIMATE CHANGES DURING THE LAST 21000 YEARS IN SW AFRICA BASED ON A MARINE POLLEN RECORD

A high resolution marine pollen record from site GeoB1023, west of the northern Namib desert provides data on vegetation and climate change for the last 21 ka at an average resolution of 185 y. Pollen and spore s are mainly delivered to the site by the Cunene river and by surface and mid-tropospheric wind systems. The main pollen source areas are lo cated between 13 degrees S and 21 degrees S, which includes the northe rn Namib desert and semi-desert, the Angola-northern Namibian highland , and the north-western Kalahari. The pollen spectra reflect environme ntal changes in the region. The last glacial maximum (LGM) was charact erised by colder and more arid conditions than at present, when a vege tation with temperate elements such as Asteroideae, Ericaceae, and Res tionaceae grew north of 21 degrees S. At 17.5 ka cal. B.P., an amelior ation both in temperature and humidity terminated the LGM but, in the northern Kalahari, mean annual rainfall in the interval 17.5-14.4 ka c al. B.P. was probably 100-150 mm lower than at present (400-500 mm/y). The Late-glacial to early Holocene transition includes two arid perio ds, i.e. 14.4-12.5 and 10.9-9.3 ka cal. B.P. The last part of the form er period may be correlated with the Younger Dryas. The warmest and mo st humid period in the Holocene occurred between 6.3 and 4.8 ka cal. B .P. During the last 2000 years, human impact, as reflected by indicati ons of deforestation, enhanced burning and overgrazing, progressively intensified.