Vegetational Change and Land Degradation in the Lake Baringo Area, Kenya, During the Late Holocene: Evidence from the Paleorecord and Remote Sensing

This dissertation investigates the history of vegetational changes and land degradation in the Lake Baringo area, Kenya, East Africa, during the Late Holocene. It uses 14C -and 210Pb-dated fossil pollen, fungal spores, microscopic charcoal, and stratigraphic record from lake-sediment cores to reconstruct the paleoenvironment in the East African region. More recent changes in the Lake Baringo are examined using remote sensing imagery. These data provide one the first high-resolution late Holocene pollen records from the semi-arid region of Kenya (and one of only a handful from East Africa in general). Lake Baringo records a sedimentation rate of 1 cm yr-1, which remained largely unchanged for both the prehistoric period, prior to European settlement in the Baringo ecosystem (AD 1890s), and after, including the present. That raised the possibility that background environmental conditions and not humans are the main drivers of land degradation in the ecosystem. A record from a 363-centimeter core retrieved from Lake Baringo reveals a largely dry environment that is punctuated by a succession of centennial- to decadal-scale wet and dry episodes, separated by rather sharp transitions, including two intense dry episodes at ca. AD 1650 and AD 1750 that led to drying of the lake. The two episodes are reflected by poor pollen preservation environment and by relatively high percentages of dry-indicator species such as Podocarpus, Olea, Euclea, Acacia, Balanitaceae, Gramineae, and Cyperaceae. However, climatic implications of the changes in pollen spectra in the Lake Baringo record are limited by the extremely high sedimentation rate in Lake Baringo that effectively constrains the chronological record of the cores to the last 300 14C yr BP. Satellite imagery analyzed in this dissertation reveals that deforestation and the resultant land degradation have contributed to increased sediment yield in the lake. Consequently, the lake surface area was reduced by over 10% and turbidity increased, which is confirmed by a statistically significant increase (t = -84.699, p \u3c0.001) in the albedo between 1986 and 2000. Although climatic variations account for some of the changes in the lake catchment most of the changes in land cover are inherently linked to mounting human and livestock population in the Lake Baringo catchment