Past environmental and climate changes in northern Tanzania: Vegetation and lake level variability in Empakaai Crater
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
This thesis presents palaeoenvironmental data from equatorial Africa covering two important time intervals; i) the warming period forming the Pleistocene/Holocene transition and ii) the last millennium. The Empakaai Crater, in northern Tanzania contains a lake from where sediment cores, spanning two time-slices 14.8-9.3 ka and 800-2000 AD, have been studied. Palaeoecological and palaeohydrological reconstruction is based on a multitude of proxies from the sediments, representing both catchment environment and the lakes aquatic ecosystem response. Between 14.8 and 10 ka the catchment vegetation and lake hydrology responded to both regional climate changes and local environment, but with different amplitude and frequency, reflecting temporal and spatial lags between the two systems. However, at c 10 ka both lake conditions and catchment vegetation showed drastic changes towards drier conditions. The record covering the last millennium reveals environmental changes related to climate and human activities. The catchment’s vegetation was affected by frequent fires, most probably human induced, while near shore vegetation responded to lake level fluctuation associated with rainfall variability. About 15 km from Empakaai Crater is an extensive abandoned irrigation system, the Engaruka complex, which was in active use between c 1400 AD and 1840 AD. By comparing a number of social and environmental factors potentially influencing the societal development at Engaruka it is shown that wet climate conditions have had positive effects on the societal development but also that dry climate conditions were not always disastrous to the society. The resemblance of the pollen taxa present is strong between the two time slices and pollen representing catchment conditions respond in similar manner in both records. The lake conditions are however very different between the two periods Thus the lake responds to both long and short term changes of variable amplitude, while the catchment vegetation seems to responds to high amplitude, low frequency changes.
Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi , 2007. , 102 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 5
palaeoecology, palaeolimnology, physical and societal factors, Holocene, Tanzania, Lake Emakat, Engaruka
Earth and Related Environmental Sciences
Research subject Physical Geography
IdentifiersURN: urn:nbn:se:su:diva-6835ISBN: 978-91-7155-455-0OAI: oai:DiVA.org:su-6835DiVA: diva2:197167
2007-06-01, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Lamb, Henry, Professor
Holmgren, Karin, ProfessorKuhry, Peter, ProfessorWesterberg, Lars-Ove, Dr
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