Letters to Nature

Nature 403, 410-414 (27 January 2000) | doi:10.1038/35000179; Received 8 April 1999; Accepted 16 November 1999

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

Dirk Verschuren1,2, Kathleen R. Laird3 & Brian F. Cumming3

  1. Limnological Research Center, University of Minnesota, Minneapolis, Minnesota 55455 , USA
  2. Department of Biology, University of Gent, Ledeganckstraat 35, B-9000 Gent, Belgium
  3. Paleoecological Environmental Assessment and Research Laboratory, Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada

Correspondence to: Correspondence should be addressed to D.V. (e-mail: Email: dirk.verschuren@rug.ac.be ). The data presented here are archived at the World Data Center-A for Paleoclimatology.

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 cores1, 2, 3. 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' (approx ad 1000–1270) and a relatively wet climate during the 'Little Ice Age' (approx 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 Africa4, highlighting the importance of a detailed knowledge of natural long-term rainfall fluctuations for sustainable socio-economic development.