Paleolimnological Investigations of Anthropogenic Environmental Change in Lake Tanganyika: IX.Summary of Paleorecords of Environmental Change and Catchment Deforestation at Lake Tanganyika and Impacts on the Lake Tanganyika Ecosystem
Loading...
Date
2005
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
Paleorecords from multiple indicators of environmental change provide evidence for the interactions between
climate, human alteration of watersheds and lake ecosystem processes at Lake Tanganyika, Africa, a
lake renowned for its extraordinary biodiversity, endemism and fisheries. This paper synthesizes geochronology,
sedimentology, paleoecology, geochemistry and hydrology studies comparing the history of
deltaic deposits from watersheds of various sizes and deforestation disturbance levels along the eastern
coast of the lake in Tanzania and Burundi. Intersite differences are related to climate change, differences in
the histories of forested vs. deforested watersheds, differences related to regional patterns of deforestation,
and differences related to interactions of deforestation and climate effects. Climate change is linked to
variations in sediment accumulation rates, charcoal accumulation, lake level and water chemistry, especially
during the arid-humid fluctuations of the latter part of the Little Ice Age. Differences between
forested and deforested watersheds are manifested by major increases in sediment accumulation rates in the
latter (outside the range of climatically driven variability and for the last 40 years unprecedented in
comparison with other records from the lake in the late Holocene), differences in eroded sediment and
watershed stream composition, and compositional or diversity trends in lake faunal communities related to
sediment inundation. Variability in regional patterns of deforestation is illustrated by the timing of transitions
from numerous sedimentologic, paleoecologic and geochemical indicators. These data suggest that
extensive watershed deforestation occurred as early as the late-18th to the early-19th centuries in the
northern part of the Lake Tanganyika catchment, in the late-19th to early-20th centuries in the northern
parts of modern-day Tanzania, and in the mid-20th century in central Tanzania. Rapid increases in
sediment and charcoal accumulation rates, palynological and lake faunal changes occurred in the early-
1960s. We interpret this to be the result of greatly enhanced flushing of sediments in previously deforested
watersheds triggered by extraordinary rainfall in 1961/62. Regional differences in deforestation histories
Journal of Paleolimnology (2005) 34: 125–145 Springer 2005
DOI 10.1007/s10933-005-2422-4
can be understood in light of the very different cultural and demographic histories of the northern and
central parts of the lake shoreline. Incursion of slaving and ivory caravans from the Indian Ocean to the
central coast of Lake Tanganyika by the early-19th century, with their attendant diseases, reduced human
and elephant populations and therefore maintained forest cover in this region through the late-19th to
early-20th centuries. In contrast, the northeastern portion of the lakeshore did not experience the effects of
the caravan trades and consequently experienced high human population densities and widespread
deforestation much earlier. These studies demonstrate the importance of paleolimnological data for making
informed risk assessments of the potential effects of watershed deforestation on long-term lake ecosystem
response in the Lake Tanganyika catchment. Differences in sediment yield and lake floor distribution of
that yield, linked to factors such as watershed size, slope, and sediment retention, must be accounted for in
management plans for both human occupation of currently forested watersheds and the development of
future underwater reserves.
Description
Full text can be accessed at
http://link.springer.com/article/10.1007/s10933-005-2422-4
Keywords
Deforestation, East Africa, Lake level, Lake Tanganyika, Late Holocene, Soil erosion
Citation
Cohen, A.S., Palacios-Fest, M.R., Msaky, E.S., Alin, S.R., McKee, B., O’Reilly, C.M., Dettman, D.L., Nkotagu, H. and Lezzar, K.E., 2005. Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: IX. Summary of paleorecords of environmental change and catchment deforestation at Lake Tanganyika and impacts on the Lake Tanganyika ecosystem. Journal of Paleolimnology, 34(1), pp.125-145.