scholarly journals Environmental change over the last millennium recorded in two contrasting crater lakes in western Uganda, eastern Africa (Lakes Kasenda and Wandakara)

2011 ◽  
Vol 30 (5-6) ◽  
pp. 555-569 ◽  
Author(s):  
David B. Ryves ◽  
Keely Mills ◽  
Ole Bennike ◽  
Klaus Peter Brodersen ◽  
Angela L. Lamb ◽  
...  
2013 ◽  
Vol 9 (5) ◽  
pp. 5183-5226 ◽  
Author(s):  
K. Mills ◽  
D. B. Ryves ◽  
N. J. Anderson ◽  
C. L. Bryant ◽  
J. J. Tyler

Abstract. Equatorial East Africa has a complex, regional patchwork of climate regimes, with multiple interacting drivers. Recent studies have focussed on large lakes and reveal signals that are smoothed in both space and time, and, whilst useful at a continental scale, are of less relevance when understanding short-term, abrupt or immediate impacts of climate and environmental changes. Smaller-scale studies have highlighted spatial complexity and regional heterogeneity of tropical palaeoenvironments in terms of responses to climatic forcing (e.g. the Little Ice Age [LIA]) and questions remain over the spatial extent and synchroneity of climatic changes seen in East African records. Sediment cores from paired crater lakes in western Uganda were examined to assess ecosystem response to long-term climate and environmental change as well as testing responses to multiple drivers using redundancy analysis. These archives provide annual to sub-decadal records of environmental change. The records from the two lakes demonstrate an individualistic response to external (e.g. climatic) drivers, however, some of the broader patterns observed across East Africa suggest that the lakes are indeed sensitive to climatic perturbations such as a dry Mediaeval Climate Anomaly (MCA; 1000–1200 AD) and a relatively drier climate during the main phase of the LIA (1500–1800 AD); though lake levels in western Uganda do fluctuate. The relationship of Ugandan lakes to regional climate drivers breaks down c. 1800 AD, when major changes in the ecosystems appear to be a response to sediment and nutrient influxes as a result of increasing cultural impacts within the lake catchments. The data highlight the complexity of individual lake response to climate forcing, indicating shifting drivers through time. This research also highlights the importance of using multi-lake studies within a landscape to allow for rigorous testing of climate reconstructions, forcing and ecosystem response.


2019 ◽  
Vol 107 ◽  
pp. 105563 ◽  
Author(s):  
Angela Nankabirwa ◽  
Wannes De Crop ◽  
Thijs Van der Meeren ◽  
Christine Cocquyt ◽  
Pierre-Denis Plisnier ◽  
...  

2019 ◽  
Vol 93 ◽  
pp. 172-186 ◽  
Author(s):  
Lawrence M. Kiage ◽  
Meghan Howey ◽  
Joel Hartter ◽  
Michael Palace

AbstractNon-pollen palynomorphs and elemental geochemistry data from Lake Kifuruka in western Uganda provide evidence of environmental change in the tropical African region since the beginning of the Holocene. The multi-proxy record presented here shows that dry conditions dominated the end of the Pleistocene evidenced by calcium enriched sediments and suppressed fungal taxa activity. Moist conditions dominated the early Holocene and persisted until just after 1960 cal yr BP. Elevated frequencies of individual fungal spore taxa associated with herbivory and soil erosion, including Sordaria-type, Sporormiella-type, Chaetomium-type, and Glomus-type, about 4300 cal yr BP suggests a significant environmental change that could be linked to human activities. A convergence of multiple proxy data, including microscopic charcoal, elemental geochemistry, and fungal spores, strongly support the occurrence of anthropogenic forest disturbance in the Albertine Rift about 4300 cal yr BP.


2020 ◽  
Author(s):  
Frank Schäbitz ◽  
Verena Foerster ◽  
Asfawossen Asrat ◽  
Andrew S. Cohen ◽  
Melissa S. Chapot ◽  
...  

<p><span>Humans </span><span>have been adapting to more demanding habitats in the course of their evolutionary history</span><span>. </span><span>Nevertheless</span><span>, environmental changes coupled with overpopulation naturally limit competition for resources. In order to find such limits, reconstructions of climate and </span><span>population changes </span><span>are increasingly used for the continent of our origin, Africa.</span> <span>However, </span><span>continuous and high-resolution records of climate-human interactions are still scarce. </span></p><p><span>Using a 280 m sediment core from Chew Bahir*, a wide tectonic basin in southern Ethiopia,</span> <span>we reconstruct the paleoenvironmental conditions during the development of <em>Homo sapiens.</em> The complete multiproxy record of the composite core covers the last ~600 ka </span><span>, allowing tests of hypotheses about the influence of climate change on human evolution and technological innovation from the Late Acheulean to the Middle/Late Stone Age, and on dispersal within and out of Africa</span><span>. </span></p><p><span>Here we present results from the uppermost 100 meters of the Chew Bahir core, spanning the last 200 kiloyears (ka). </span><span>The record shows two modes of environmental change that are associated with two types of human mobility. The first mode is a long-term trend towards a more arid climate, overlain by precession-driven wet-dry alternation. Through comparison with the archaeological record, humid episodes appear to have led to the opening of ‘green’ networks between favourable habitats and thus to increased human mobility on a regional scale. The second mode of environmental change resembles millennial-scale Dansgaard-Oeschger and Heinrich events, which seem to coincide with enhanced vertical mobility from the Ethiopian rift to the highlands, especially in the time frame between ~65–21 ka BP. The coincidence of climate change and human mobility patterns help to define the limiting conditions for early <em>Homo sapiens</em> in eastern Africa.</span></p><p><span>___________________</span></p><p><span>*</span> <span>cored in the context of HSPDP (<em>Hominin Sites and Paleolakes Drilling Project</em>) and CRC </span><span>(<em>Collaborative Research </em><em>Centre</em>) 806 “<em>Our way to Europe</em>”</span></p>


2021 ◽  
Author(s):  
Graciela Gil-Romera ◽  
Lucas Bittner ◽  
David A. Grady ◽  
Laura S. Epp ◽  
Götz Ossendorf ◽  
...  

<p><span>The advent of pastoralism in Eastern Africa is one of the most significant cultural transformations in the continent’s history. Traditionally, herding origins and its spreading routes have been studied in the lowlands and described as a complex and lengthy process that began before 4 ka BP and lasted until 1.3 ka BP. This cultural transition has long been argued to have been a process involving both environmental change and population movements. </span><span>Given the current patchy </span><span>archaeological data, most studies studies conclude that no single factor can be identified as a driver of the onset of herding in Eastern Africa, but almost all evidence is from lowland areas. The higher elevations of the Eastern African mountains are sensitive to climate and environmental change, so may be ideal for testing hypotheses of human-environmental relationships. However, the history of pastoralism in the African highlands, especially its connection with regional herding migrations and Holocene climate change, has thus far been poorly explored with few available records. </span></p><p><span> In this contribution, we provide evidence of early pastoral activities at high altitude in the Bale Mountains of southwest Ethiopia. We present a 4000-year multiproxy palaeoecological lacustrine sequence from Garba Guracha, a cirque lake at 3950 m asl, combining palaeoclimatic and palaeoenvironmental proxies. Our record indicates the distinctive presence of faecal fungal spores (</span><span><em>Sporormiella, Cercospora, Podospora</em></span><span>) and the expansion of pollen and </span><span><em>seda</em></span><span>DNA from ruderal plants as early as 3.5 ka. To our knowledge, this is the highest altitude record of early animal husbandry traces on the continent. Coeval with the expansion of pastoralism indicators in Garba Guracha, we find important changes in the lake’s diatom community, as well as climate fluctuations reconstructed from biomarkers; these may be critical for understanding human occupation at high altitudes. However, archaeological studies conducted in the Garba Guracha basin have proved unfruitful in finding permanent settlements of herders, </span><span>suggesting</span><span> hypothes</span><span>es</span><span> of seasonal resource use. </span></p><p><span> We discuss different scenarios of pastoral expansion on the Eastern African highlands under changing local climates, as well as the general context of pastoralist migration across Eastern Africa. </span></p>


The Holocene ◽  
2000 ◽  
Vol 10 (4) ◽  
pp. 527-536 ◽  
Author(s):  
D. Taylor ◽  
P. Robertshaw ◽  
R. A. Marchant

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