Daniel O. Olago

Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya

Hominin footprints offer evidence about gait and foot shape, but their scarcity, combined with an inadequate hominin fossil record, hampers research on the evolution of the human gait. Here, we report hominin footprints in two sedimentary layers dated at 1.51 to 1.53 million years ago (Ma) at Ileret, Kenya, providing the oldest evidence of an essentially modern human–like foot anatomy, with a relatively adducted hallux, medial longitudinal arch, and medial weight transfer before push-off. The size of the Ileret footprints is consistent with stature and body mass estimates for Homo ergaster/erectus, and these prints are also morphologically distinct from the 3.75-million-year-old footprints at Laetoli, Tanzania. The Ileret prints show that by 1.5 Ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion.

Mitigation of environmental problems in Lake Victoria, East Africa: causal chain and policy options analyses

Abstract Lake Victoria is an international waterbody that offers the riparian communities a large number of extremely important environmental services. Over the past three decades or so, the lake has come under increasing and considerable pressure from a variety of interlinked human activities such as overfishing, species introductions, industrial pollution, eutrophication, and sedimentation. In this paper we examine the root causes for overfishing and pollution in Lake Victoria and give possible policy options that can help remediate or mitigate the environmental degradation.

The east African great lakes : limnology, palaeolimnology and biodiversity

Introduction. Acknowledgements. Geological and Structural Setting of the East African Lakes. A 300 Million Years History of Rift Lakes in Central and East Africa: An Updated Broad Review J.-J. Tiercelin, K.-E. Lezzar. Climate Dynamics and Climate Variability in the East African Lakes Region. Extreme Rainfall Events and Lake Level Changes in East Africa: Recent Events and Historical Precedents D. Conway. Mesoscale Patterns of Rainfall, Cloudiness and Evaporation Over the Great Lakes of East Africa S.E. Nicholson, X. Yin. Observations, Evaporation and Preliminary Modelling of Over-Lake Meteorology on Large African Lakes P.F. Hamblin, et al. Development of a Coupled Regional Climate Simulation Model for the Lake Victoria Basin Y. Song, et al. Hydrology and Physical Limnology. A Modelling Approach for Lake Malawi/Nyasa/Niassa: Integrating Hydrological and Limnological Data D.C.L. Lam, et al. Ventilation of Lake Malawi/Nyasa M.K. Vollmer, et al. Application of Satellite AVHRR to Water Balance, Mixing Dynamics, and the Chemistry of Lake Edwards, East Africa J.T. Lehman. Lake-Groundwater Relationships, Oxygen Isotope Balance and Climate Sensitivity of the Bishoftu Crater Lakes, Ethiopia S. Kebede, et al. A Review of Sediment Gas Cycling in Lakes with reference to Lake Victoria and Sediment Gas Measurements in Lake Tanganyika D.D. Adams, S.O. Ochola. Biodiversity, Food Webs and Fisheries. Redundancy and Ecosystem Stability in the Fluctuating Environments of Long-Lived Lakes K. Martens. Invasion of Lake Victoria by the Large Bodied Herbivorous Cladoceran Daphnia Magna R. Jonna, J.T. Lehman. Effects of Climate and Human Activities on the Ecosystem of Lake Baringo, Kenya P.A.Aloo. Limnological Profiles and their Variability in Lake Tanganyika P.-D. Plisnier. Sedimentary Processes, Paleoclimate and Paleoenvironment. Sedimentology and Geochronology of Late Pleistocene and Holocene Sediments from Northern Lake Malawi S.L. Barry, et al. A 24,000 yr Diatom Record from the Northern Basin of Lake Malawi F. Gasse, et al. Lake Tanganyika Holocene Record on Variability in Precipitation in the Malagarasi Catchment Basin A.N. Muzuka, N. Nyandwi Late Quaternary Sedimentation and Climate in the Lakes Edward and George Area, Uganda-Congo T. Laerdal, et al. Pigment Analysis of Short Cores from the Central Ethiopian Rift Valley Lakes M.U. Mohammed, et al. Origin and Isotopic Composition of Aragonite Laminae in an Ethiopian Crater Lake H. Lamb, et al. Vegetation Changes and their Climatic Implications for the Lake Victoria Region during the Late Holocene I. Ssemmanda, A. Vincens. Organic Content and X-ray Density of Lacustrine Sediments from Hausberg Tarn, Mount Kenya W. Karlen, et al. Human Dimensions: Impacts and Management. Restoring and Protecting the African Great Lake Basin Ecosystems -- Lessons from the North American Great Lakes and the GEF A.M. Duda. Geological Hazards and Anthropogenic Impacts on the Environment in Malawi: Lesson from a Case Study of Debris Flows in Zomba J. Mwenelupembe, H.-G. Mylius. The Human Dimensions Studies on the East African Lake Regions: A Review M.M. Opondo.

Late Quaternary glacial-interglacial cycle of climatic and environmental change on Mount Kenya, Kenya

Abstract Sediments from Sacred Lake and Lake Nkunga on the northeastern flank of Mount Kenya have a sequential palaeoclimatic and palaeoenvironmental record covering most of the Late Quaternary period: from ca 115 to 0 ka. Most of the Late Quaternary period (110 to 14 ka - glacial period) was characterised by terrestrial C 4 vegetation types (grassland) at higher altitudes and mixed C 3 –C 4 (grassland with scattered trees and shrubs) vegetation types at lower altitudes, while low, productivity-related 13 C discrimination occurred in the aquatic environment. The last interglacial and Holocene vegetation consisted of C 3 forest-type elements, and high 13 C discrimination occurred in the aquatic environment. The period 14 to 9 ka is transitional to Holocene climatic conditions, with progressive expansion of terrestrial C 3 vegetation, and increased 13 C discrimination in the aquatic environment. These changes occurred in step with, and were primarily driven by, palaeo-atmospheric CO 2 changes. Thus, the estimates of temperature depression in the tropics during the last glaciation need to be revised as they are probably overestimated. Regionally, the changes on Mount Kenya are coherent with those observed at other high altitude sites across the tropics. Globally, they show a high coherency with Milankovitch periodicities, and are coupled to ocean circulation changes and ice sheet growth and disintegration cycles in the North Atlantic.

Environmental assessment of the East African Rift Valley lakes

An assessment of the East African Rift Valley lakes was initiated by the United Nations Environment Programme (UNEP) with funding from Global Environment Facility as part of the Global International Waters Assessment (GIWA). The purpose of GIWA was to produce globally comparable assessments and examine stresses on international waters: marine, coastal and fresh; surface and groundwaters. The assessment of the East African Rift Valley lakes was undertaken from the perspective of water quality and quantity, associated biodiversity and habitats, their use by society and societal causes of the regionally identified issues and problems. Assuming intrinsic values of aquatic ecosystems, the assessment of social perspective focused on human use of water and considered the incremental costs of measures to encourage sustainable development. The assessment identified the major concerns facing the East African Rift Valley lakes.By and large, pollution and unsustainable exploitation of fisheries and other living resources emerged as critical concerns attributable to human activities. East Africa has a very high concentration of humans and economic activities. Pollution is from uncontrolled discharge of wastes directly into the lakes. Unsustainable exploitation of fisheries and other living resources is caused by over-fishing, destructive fishing practices, and introduction of non-native species that affect the composition of the native communities, resulting sometimes in the collapse of certain species and dominance by resilient ones. Loss of biodiversity also was identified as a major concern; and the issues of excessive by-catch and discards are also relevant. Trawling using undersized mesh-nets for target species and indiscriminate fishing gear or poison is serious, in most cases resulting in indiscriminate catches, including juvenile fish. Given the transboundary nature of the issues identified in this assessment, appropriate multilateral policy and institutional arrangements need to be established in East Africa to address the main concerns of these large lakes. Riparian countries must pay attention to the regional management of these transboundary water bodies, and appropriate planning of human population sizes and their settlement, land-use and waste disposal to control pollution. Although East African lakes contribute relatively little emission of greenhouse gases, there is a need to reduce the rate of deforestation and even restore cleared areas since forests serve as sinks of greenhouse gases towards mitigating adverse climatic changes.

Long-term temporal characteristics of palaeomonsoon dynamics in equatorial Africa

Abstract In this paper we examine the long-term temporal characteristics of palaeomonsoon dynamics in equatorial Africa from a continuous lacustrine sequence retrieved from Sacred Lake, Mount Kenya (0°03′N, 37°32′E, 2350 m a.s.l.), covering the last interglacial–glacial transition to the present. The trends in mineral magnetics and stable carbon isotopes are proxy indicators of changes in precipitation on the mountain over the last glacial–interglacial cycle. Spectral analysis by a fast fourier transform method revealed that the stable carbon isotope trend (δ 13 C) has strong signals at the 23,000 and 11,500 year frequencies. The mineral magnetic signature does not register the 23,000 year cycle observed in the δ 13 C signature. It has, however, a strong signal at an 11,500 year frequency, and sharp but relatively weak peaks at ca. 7500 and 5000 year frequencies are recorded. The dominant 23,000 year frequency recorded in the δ 13 C signature reflects the strong effect of the precessional cycle on tropical climate and ecosystems, and is most probably effected via global atmospheric pCO 2 and temperature changes. The shorter cycles at 11,500 year (indicated by both mineral magnetics and δ 13 C trends), and 7500 and 5000 years BP (apparent in the mineral magnetic record) are attributed to precipitation variations, whose temporal cycles are dominated by the higher precessional harmonics.

Holocene palaeohydrology, groundwater and climate change in the lake basins of the Central Kenya Rift

Abstract The Central Kenya Rift contains small soda lakes such as Nakuru, Elmenteita and Bogoria, freshwater Lake Naivasha, and the partly (spatially) freshwater Lake Baringo. The hydrology of this area is controlled mainly by climate, tectonically controlled morphological and volcanic barriers, faults, and local water-table variations. Much of the area relies on groundwater for human and industrial use, though there are widespread quality issues particularly in relation to fluoride. Despite the huge demand for the resource, little is known about the highly complex groundwater systems; lacking monitoring data, an assessment is developed on the basis of regional geological, hydrogeological and hydrochemical analyses. Significant hydrological changes have taken place in the region over the last 10 000 years as a result of global, regional and local changes, but the impacts on groundwater resources are still largely unknown. The IPCC projects a 10–15% increase of rainfall in the area, but it may not necessarily result in a proportional increase in groundwater recharge. High groundwater recharge periods appear to be anchored on a decadal cycle.

The tropical lapse rate steepened during the Last Glacial Maximum

A new temperature record from East Africa demonstrates that the tropical lapse rate steepened during the last ice age. The gradient of air temperature with elevation (the temperature lapse rate) in the tropics is predicted to become less steep during the coming century as surface temperature rises, enhancing the threat of warming in high-mountain environments. However, the sensitivity of the lapse rate to climate change is uncertain because of poor constraints on high-elevation temperature during past climate states. We present a 25,000-year temperature reconstruction from Mount Kenya, East Africa, which demonstrates that cooling during the Last Glacial Maximum was amplified with elevation and hence that the lapse rate was significantly steeper than today. Comparison of our data with paleoclimate simulations indicates that state-of-the-art models underestimate this lapse-rate change. Consequently, future high-elevation tropical warming may be even greater than predicted.

Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study.

Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02-75 mg/L. 73% exceed the health limit (1.5mg/L) in both dry and wet seasons. F(-) concentrations in rivers are lower (0.2-9.2mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27-75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ(18)O) and hydrogen (δD) isotopic values range from -6.2 to +5.8‰ and -31.3 to +33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750-6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (<1000 ppm). Thus, geochemical F(-) enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments.

Sediment impacts in Africa's transboundary lake/river basins: Case study of the East African Great Lakes

The current population pressure, inappropriate cultivation practices, forest removal and high grazing intensities on forests, wetlands, rangelands and marginal agricultural lands leads to unwanted sediment and stream flow changes that mainly impacts the downstream human and natural communities. Forests and bush are cleared, and wetlands are encroached to create space for human settlement, roads construction and to satisfy wood fuel energy demands. Similarly, pastoral areas are subjected to growing human and livestock populations, leading to land degradation, soil erosion and to an increase in the load of non-point pollutants. Landscape disturbance over many decades, and the resulting increase in soil erosion and sedimentation is the dominant cause of the ongoing eutrophication in many of the lakes in eastern Africa. Increased sedimentation in the rivers and lakes has many impacts. For example, it has altered some aquatic habitats and communities, contributed to increasing eutrophication, abetted the proliferation of algal blooms and water hyacinth reduced the amount of dissolved oxygen, etc. This paper outlines some of the problems created by increased sedimentation within the East African Great Lakes basin, and provides some possible solutions to the mitigation of sediment flux through integrated sediment management approaches.