This study presents results fromii a multi-proxy anialysis of cores taken in a crater-lake sequence fromll Eski Acigol in centr-al Turkey which cover the period fromii pre-c. 1600X) cal. yr BP to the present. The sediments comiiprise an upper unit of enerally non-laminated, banded to massive silts and peats of mid-to late-Holocene age, oveilying a laminated tinit of late-Pleistocene to early/miid-Holocenie age. The lamiinlae, comprising mainily aragonite. amorphous silica (diatom trustules) and organic mattei were formed in a relatively deep, dilute. meromiiictic lake. Pollen data indicate an abrupt replacement of Ar;eyisi'io-chenopod steppe by grass-oakterebinth parkland during the period of laminae deposition, imiar-king the start of the Holocenie. A gradual Li i E ;i E; increase in tree pollen during the early Holocene came to a i n end c. 6500 cal. yr BP (U-series and adjusted 4C timescale), when mesic deciduotLs taxa declined at the same timiie as lake levels fell. Human impact on regional vegetation is infened from a sharp decline in oak arotind 4500-.4(X0)0 cal. yr BP. Diatom, isotopic anid mineralogical data indicate that during the second half of the Holocene the lake became relatively shallow and A oscillated between fresh and brackish/evaporated water conditions. The contrast between wetter early-and drier HOLOCENE late-Holocene climatic conditions is matched bv other eastern anid central Mediterranean proxy climate data. SPECIAL ISSUEWhile the Eski Acigol seqtLience resembles Holocene hydroclimatic changes in the Saharo-Arabian zone and was also apparenitly linlked to orbital forcing, it is unlikely to have had the samlle direct cause, i.e., an expansion and subsequent retreat of monsoon rainfall.

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This review paper synthesizes the recent published palaeoecological results obtained in Atlantic Equatorial Africa (ECOFIT program) on the history of forest ecosystems and inferred climate changes during the past 4000 years. Evidence are mainly provided by pollen analysis carried out at nine sites from Congo, Cameroon and Ghana, locally supported by macroflora remains, phytoliths, diatoms, 13 C and mineralogical data. At all the sites, except Lake Bosumtwi (Ghana), following a large expansion of rain and mesophilous forests until 3000 years BP, a major change is registered, affecting floristic composition, structure and geographical distribution. According to the hydrological sensitivity of the different sites, local openings of the forests with development of heliophilous formations and/or isolated enclosed savannas are observed at the most humid sites; complete disappearance of forested formations at the driest. The agreement between pollen records, hydrological and hydrobiological data definitely demonstrates that an arid event has been the primary driving factor of this change and is responsable for the main features of the modern landscapes in Atlantic Equatorial Africa. Moreover, the most recent palaeoecological data obtained in Congo (Lake Sinnda), indicate that this Late Holocene increasing aridity was of longer duration, from 4000 to 1300 years BP, and more progressive than previously inferred. A new expansion of forests is locally detected c. 900-600 BP despite increased human impact.

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Today, precipitation over tropical South America is largely controlled by the seasonal movements of the Inter-Tropical Convergence Zone (ITCZ). During the summer, the ITCZ is shifted southward due to the warming of the continent. Paleoclimate data from southeastern Amazonia and the central Andes indicate that these two areas evolved similarly during the last 30,000 yr. However, between 12,400 and 8800 cal yr B.P., eastern Amazonia received substantial moisture whereas the Bolivian Altiplano was arid. This suggests that the ITCZ during summer was then farther north than it is today.