Rainfall and drought in equatorial east Africa during the past 1,100 years

Rainfall and drought in equatorial east Africa during the past 1,100 years
Nature, No.6768, v403, pp 410-414, January 27, 2000

Dirk Verschuren
Limnological Research Center, University of Minnesota, Minneapolis, Minnesota 55455, USA, and Department of Biology, University of Gent, Ledeganckstraat 35, B-9000 Gent, Belgium

Kathleen R. Laird and Brian F. Cumming
Paleoecological Environmental Assessment and Research Lab, Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada

Knowledge of natural long-term rainfall variability is essential for water-resource and land-use management in sub-humid regions of the world. In tropical Africa, data relevant to determining this variability are scarce because of the lack of long instrumental climate records and the limited potential of standard high-resolution proxy records such as tree rings and ice cores. Here we present a decade-scale reconstruction of rainfall and drought in equatorial east Africa over the past 1,100 years, based on lake-level and salinity fluctuations of Lake Naivasha (Kenya) inferred from three different palaeolimnological proxies: sediment stratigraphy and the species compositions of fossil diatom and midge assemblages. Our data indicate that, over the past millennium, equatorial east Africa has alternated between contrasting climate conditions, with significantly drier climate than today during the 'Medieval Warm Period' (~AD 1000-1270) and a relatively wet climate during the 'Little Ice Age' (~AD 1270-1850) which was interrupted by three prolonged dry episodes. We also find strong chronological links between the reconstructed history of natural long-term rainfall variation and the pre-colonial cultural history of east Africa, highlighting the importance of a detailed knowledge of natural long-term rainfall fluctuations for sustainable socio-economic development.

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To read or view the full study, please visit the Nature website. It was published in Nature No.6768, v403, pp 410-414, January 27, 2000.

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2000 January 27