Forest response to climate changes in Atlantic Equatorial Africa during the last 4000 yearsBPand inheritance on the modern landscapes
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, δ13C and mineralogical data.
At all the sites, except Lake Bosumtwi (Ghana), following a large expansion of rain and mesophilous forests until 3000 yearsBP, 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 yearsBP, and more progressive than previously inferred. A new expansion of forests is locally detected c. 900–600BPdespite increased human impact.
Document Type: Research Article
Affiliations: 1: CEREGE, BP 80, 13545 Aix-en-Provence cedex 04, France 2: ORSTOM, CEREG, 3 rue de l’Argonne, 67083 Strasbourg, France 3: Paléoenvironnements et Palynologie, Université de Montpellier 2, 34095 Montpellier cedex 5, France 4: ORSTOM Ile de France, 32 avenue Henri Varagnat, 93143 Bondy cedex, France 5: Biochimie Isotopique, Université Paris VI, case 120, 4 place Jussieu, 75252 Paris 05, France 6: ORSTOM, Géologie, Museum National d’Histoire Naturelle, 43 rue Buffon, 75005 Paris, France
Publication date: July 1, 1999