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After the flood and with the people – Late Holocene changes of the woody vegetation in the southwestern Chad Basin, Nigeria
Abstract
The development of cultivated landscapes under the influence of food production has decisively shaped the composition and appearance of West African savannas as present today. With trees and shrubs forming an important constituent of such landscapes, and its composition characterizing different types of land-use, anthracology is a tool particularly well suited to trace developments and changes through human exploitation of the landscape. Within the West African savanna belts, regions shaped by prolonged annual floods, such as the Middle Senegal Valley, the Inland Niger Delta and the Chad Basin, offer particular ecological preconditions for land-use. We present here a charcoal study for the Chad Basin of northeast Nigeria, demonstrating the special development of a cultivated landscape in an alluvial context. Charcoal samples from stratified Late Stone Age and Iron Age sites within the southwestern Chad Basin, Nigeria were analyzed. Main focus is on the site Mege, spanning more than 2500 years of occupation history. The results are supplemented with and compared to data from other, earlier as well as contemporary sites, in similar or slightly different environments and representing different settlement types, in order to discern general trends.
... On the other hand, woody savannah biomes such as Mege, in the floodplain environment of Gajiganna in what is now northeastern Nigeria, have undetectable changes in the charcoal composition associated with the introduction of livestock after ca. 3.8 ka and only minor changes with Iron Age settlement after 2.4 ka (Höhn et al., 2021). The persistence of generally wetter biome until ca. ...
... Across western Africa, the identification of anthropogenic parklands resulting from clearance of woody vegetation occurs in a variety of ecological contexts and can be particularly difficult to identify in riparian settings particularly when modelled with natural climate variability (Heinrich and Moldenhauer, 2002;Höhn et al., 2021). Early Iron Age sites from northern Burkina Faso show widespread cultivation interspersed with long intervals of fallowing from ca. 2 to 1 ka after which shorter fallow periods and more intensive livestock production as well as decreasing precipitation resulted in the creation of a more open (grassy) landscape . ...
... Domestication of wild plant species and arboriculture by farmers in the Usambara Mountains, Tanzania have been documented as a means of conserving local plant diversity, which has recursive effects enhancing ex-situ microbial and faunal biodiversity (Msuya et al., 2008;Munishi et al., 2008). In prehistoric Fayum, limited, selective coppicing of tamarisk (Tamarix sp.) yielded only minimal disturbances to overall species abundance of different woodland communities (Marston et al., 2017), similar to the effects reported in the Chad Basin discussed above (Höhn et al., 2021). ...
As the continent with the deepest record of human history, the relationship between landscape formation and human subsistence practices is inseparable. The activities that constitute 'farming' are open for some matter of discussion, but essentially speak to the co-evolution of human, plant and animal reproductive systems along a continuum of interdependence. This process is ever evolving, but has resulted in the formation of landscapes in which anthropogenic processes characterize ecosystem functionality in nearly all biomes on the continent. Practices of cultivation, broadly conceptualized, across Africa are varied in the ways in which they have transformed ecological systems and landscapes. The use of fire as a landscape management tool dates to the Pleistocene, and penning of wild sheep to the early Holocene. The alteration of the landscape of fear by these types of human activities had fundamentally restructured trophic systems in Africa prior to the introduction of agriculture. However, the introduction of animal herding and intensive forms of plant cultivation by the middle Holocene correlated to even more significant ecological changes. The creation of agricultural landscapes has had a negative impact on biodiversity in some locations, whereas other some practices at different points in time have positively affected biodiversity. It is now recognized that humans have long influenced the evolution of landscapes wherever they live, but the current research focuses on where, when and how socio-ecological processes become coupled in the palaeoecological record.
... Wood charcoal identification has already shown its reliability to reconstruct past African woody environments, especially in the Sahara, West and South Africa (e.g. Neumann 1989Neumann , 1992Neumann , 1999Ballouche and Neumann 1995;Höhn 1999Höhn , 2022Allott 2006;Höhn andNeumann 2012, 2016;Cartwright 2013;Hubau et al. 2013Hubau et al. , 2014Eichhorn and Neumann 2014;Höhn et al. 2021). Anthracological studies are much rarer for Eastern Africa and so far, in Ethiopia, have only been applied in the Tigray region (Gebru et al. 2009;Ruiz-Giralt et al. 2021) and the Bale Mountains (Beldados et al. 2022). ...
The SW highlands of Ethiopia are a key component in the evolution of modern humans. Yet, palaeoecological studies, essential to understand past human-vegetation relationships, are almost inexistent in this region. In this paper, we present an anthracological study of the Sodicho rock shelter, located at 1,930 m a.s.l. in the SW Ethiopian Afromontane forest zone, reconstructing the past woody vegetation since the end of the African Humid Period (ca. 5,000 cal bp). Our results show that the vegetation around the rock shelter from ca. 4,750 to 1,750 cal bp was an ecotone between Afromontane forest and wooded grasslands of the lowlands, maintained open by the use of fire, although the climatic conditions were favourable for closed forest. The charcoal assemblage also demonstrates strong wood selection, with Syzygium guineense, Acacia and Proteaceae as the preferred taxa, even during a volcanic event when human occupation had been assumed to be absent. We therefore suggest that the rock shelter might have been visited more continuously than previously thought. Finally, under less intense occupation activities from ca. 1,700 to 300 cal bp, forest taxa became comparatively more dominant than before, as documented in the charcoal record. This demonstrates that the forest can recover under reduced human impact. The fact that the Afromontane forest is resilient is of utmost importance, indicating that reforestation is still possible despite the strong agricultural and demographic pressures the Ethiopian highlands are currently facing.
... The information on the developments at Lake Chad is summarized in Höhn et al. (2020). You can learn more about some of the southern African sites where crops were found in Olatoyan et al. (2022). ...
Farming has changed the face of the earth in Africa as much as elsewhere. But histories of African farmscapes, shaped by millennia of agriculture, are obscured by narratives of pristine landscapes, whether of forests or savanna, and the role of farming in transforming African farmscapes is seldom taught in schools. We present examples of farming strategies and systems from western and southern Africa, which we hope are inspiring and maybe, at times, even surprising. Our exploration of the farmscapes, structured along the classical elements of Earth, Fire, Water, and Air, describes how plants and people deal with the influence these elements have on successful farming and how these influences show up in farmscapes. We hope these stories of flexibility, adaptation, and success and failure motivate teachers and students to think out of the box in grappling with the challenges our world is facing. These stories also provide opportunities for teaching about the United Nations Sustainable Development Goals (SDGs), particularly the goals of Zero Hunger (SDG 2), Responsible Consumption and Production (SDG 12), and Life on Land (SDG 15).
The Ihò Eléérú (or Iho Eleru) rock shelter, located in Southwest Nigeria, is the only site from which Pleistocene-age hominin fossils have been recovered in western Africa. Excavations at Iho Eleru revealed regular human occupations ranging from the Later Stone Age (LSA) to the present day. Here, we present chronometric, archaeobotanical, and paleoenvironmental findings, which include the taxonomic, taphonomic, and isotopic analyses of what is the only Pleistocene faunal assemblage documented in western Africa. Our results indicate that the local landscape surrounding Iho Eleru, although situated within a regional open-canopy biome, was forested throughout the past human occupation of the site. At a regional scale, a shift from forest- to savanna-dominated ecotonal environment occurred during a mid-Holocene warm event 6,000 years ago, with a subsequent modern reforestation of the landscape. Locally, no environmental shift was observable, placing Iho Eleru in a persistent forested "island" during the period of occupation.
This brief report describes the animal bones from the first millennium BC discovered during Graham Connah’s excavations at Daima Mound in northeastern Nigeria in 1965–66. The faunal research was completed by the author in 1973, but, owing to various circumstances, it has not been possible to publish the report until now. Eighty percent of the 657 positively identified bones come from domestic cattle, probably a small-statured breed. They were mostly slaughtered while young adults, which suggests they were surplus males. Small stock, probably goats, and also hunting were less important. The inhabitants consumed shallow water fish, mainly Clariidae (catfish), easily trapped in shallow pools. The small Daima collection confirms faunal data from other Lake Chad sites, which show that cattle herding was an important activity during the first millennium BC .
Climate variability/change has varied impacts on crop yields in many Sub-Saharan African countries. Enhancing the adaptive capacity of rural farmers is a major challenge as climate change becomes threatened to agricultural activities in the region. In this study, the impacts of climate change on cassava crops were examined, and farmers’ perceptions of climate, change and their experienced adaptation methods were assessed. Historical climate data and social datasets were used; the adaptation option and barriers to the use of adaptation methods were obtained through questionnaires, semistructured interviews and focus group discussions. Correlation statistics and multiple regressions were utilized to show the impacts of climate on the yield of cassava. The results showed a high variation in climatic variables together with an obvious anomaly index with severity. Minimum and maximum temperatures correlated strongly and positively with the yield of cassava, with 0.86, 0.82 and 0.87, respectively, which were significant at p>0.05. The results of multiple regression showed that climate parameters accounted for 75% of the changes in yield. The results also showed a very strong relationship between crops and rainfall in the early growing season at the p<0.05 level of significance. The majority of the farmers perceived that lack of capital and financial, physical and human capital accounted for 70% of barriers to the implementation of climate change adaptation methods. The key findings here are that the cropping system has been impacted by climate change and that the adaptive capacity of rural farmers in the study area is generally low. The study concludes that although climate change is obvious, there is generally a need to enhance the adaptation options available to farmers in the region.
Many societal and environmental changes occurred between the 2nd millennium BC and the middle of the 2nd millennium AD in western Africa. Key amongst these were changes in land use due to the spread and development of agricultural strategies, which may have had widespread consequences for the climate, hydrology, biodiversity, and ecosystem services of the region. Quantification of these land-use
influences and potential feedbacks between human and natural systems is controversial, however, in part because the archaeological and historical record is highly fragmented in time and space. To improve our understanding of how humans contributed to the development of African landscapes, we developed an atlas of landuse practices in western Africa for nine time-windows over the period 1800 BC–AD 1500. The maps are based on a broad synthesis of archaeological, archaeobotanical,
archaeozoological, historical, linguistic, genetic, and ethnographic data, and present land use in 12 basic categories. The main differences between categories is the relative reliance on, and variety of, domesticated plant and animal species utilized, and the energy invested in cultivating or keeping them. The maps highlight the irregular and frequently non-linear trajectory of land-use change in the prehistory of western Africa. Representing an original attempt to produce rigorous spatial synthesis from diverse sources, the atlas will be useful for a range of studies of human–environment interactions in the past, and highlight major spatial and temporal gaps in data that may guide future field studies.
Identification of archaeological or soil charcoal in a species-rich biome, such
as the Central African rainforest, is challenging because of the large number of
woody taxa with similar and overlapping wood anatomical features. Valid environmental
or archaeological interpretations can only derive from reliable and
transparent identifications that allow comparison of and referencing between
different charcoal assemblages. The identification of 30 archaeological charcoal
types from the site Dibamba in southern Cameroon serves as a starting point for
a discussion on classification and naming. These 30 types are fully documented
and illustrated in the Supplementary Online Material (SOM). The discussion
underlines the basics of “good practice” of charcoal identification in a speciesrich
tropical environment.
Settlement activities of the Nok Culture considerably decreased
around 400 BCE and ended around the beginning of
the Common Era. For a better understanding of the decline
of the Nok Culture, we studied the charcoal assemblage of
the post-Nok site Janruwa C, dating to the first centuries CE.
Janruwa C differs from Middle Nok sites in ceramic inventory
and a wider set of crops. 20 charcoal types were identified.
Most taxa are characteristic of humid habitats such as riverine
forests, while those savanna woodland charcoal types that
had been dominant in Middle Nok samples are only weakly
represented. The differences between the Middle Nok and
post-Nok assemblages do not indicate vegetation change, but
rather different human exploitation behaviors. It seems that
the Nok people avoided forest environments while in the first
centuries CE, other, possibly new populations settled closer
to the forest and were more familiar with its resources. The
new exploiting strategies might be explained as adaptation to
changing environmental conditions. Our results, together with
data from other palaeo-archives in the wider region, point
to climatic change as a potential factor for the decline of the
Nok Culture. We argue that erosion on the hill slopes, maybe
due to stronger seasonality, was responsible for land degradation
after 400 BCE and that the Nok people were not flexible
enough to cope with this challenge through innovations.
Settlement mounds in the Chad basin of north-east Nigeria provide excellent archaeobotanical evidence for the use of wild and domesticated grasses over the last 4000 years. Plant impressions in potsherds were investigated from Gajiganna. Casts of these well-preserved impressions revealed Paniceae and wild rice together with the earliest domesticated Pennisetum americanum in the area, dating to 1200–1000 cal BC. The occupation of Gajiganna ended when the occupation at Kursakata and Mege began, around 1000–800 cal BC. The macroremains of these two mounds indicate two different patterns of plant use. In Kursakata, one of the oldest domesticated Pennisetum americanum in West Africa was found charred together with wild grasses, mostly of the tribe Paniceae. In contrast to this mixed agriculture and hunter-gatherer economy, subsistence at Mege was probably based on wild grasses.
Significance
North Africa was wetter 15,000–5,000 years ago than today, with wetlands and lakes formed in the Sahara due to an enhanced monsoon. We reconstruct the lake-level history of Lake Mega-Chad, when it was the largest African lake, and demonstrate that this humid period ended abruptly 5,000 years ago, indicating that the African monsoon exhibits a nonlinear response to insolation forcing. The northern basin of Lake Mega-Chad, currently the world’s greatest dust source, became dry around 1,000 years ago. Prior to that time dust output from the northern basin would have been limited, and suggestions that this dust plays an important role in fertilizing Atlantic and Amazonian ecosystems are either overstated or only true for the last thousand years.
In the Niger Bend, many studies have shown the existence of settlement mounds which mainly developed between the 1st millennium BC and the 15th century AD. While knowledge about tell-type sites in sub-Saharan Africa has advanced in recent years, many aspects of this topic remain poorly understood. Considering the vast geographic area and time span, there is very little accurate chronostratigraphic information available. This relative lack of long sequences strongly limits the diachronic integration of cultural, economic and environmental data, necessary to unravel the socio-economic mechanisms underlying the emergence and development of this type of site. In this paper, we present the results of the excavations we recently conducted on a group of settlement mounds at Sadia, on the Seno Plain (Dogon Country, Mali), which allow a precise chronological, cultural and environmental sequence to be defined. By combining this work and the results from an extensive approach applied throughout the Dogon Country for more than fifteen years, we provide a scenario for the Seno tells and an insight into the development of Sahelian rural societies, including considerations on their interactions with the early State polities of the Niger Bend, prior to AD 1400.
Studies on land use in Africa have usually been carried out by ethnolo-gists or human geographers and were rarely concerned with data on the physical conditions of soil. There is hardly any issue, however, where interdependencies between natural and cultural factors are as evident as in the topic of land use. For this project the approach of three ethnolo-gists, Braukämper, Kirscht and Platte, was therefore combined with the analysis of Thiemeyer as physical geographer. The area of research is the Local Government Area of Marte in the Nigerian State of Borno. As part of the Chad Basin this region is mainly characterised by clay sediments which are commonly labelled firgi by its inhabitants. Beside this general term, however, the local peasants clearly distinguish five types of soil (Kanuri: katti), to which different physical conditions and qualities with respect to their cultivation are attributed. The question arose how far can this popular knowledge, accumulated by agricultural experiences over generations, be correlated with scientific data. That is why samples of the mentioned types of soil were collected by the members of our team and analysed in the laboratory of the Frank-furt Institute of Physical Geography. The detailed presentation of this analysis has to be preceded by the classification of the respective soil types in the terminology of the indigenous farmers. Ethnological studies are carried out among the two major ethnic groups of eastern Borno, the Kanuri and the Shuwa Arabs. The Kanuri have been settlers of the firgi plains for as long as they appeared in his-tory as an identifiable ethnic unity in the 16th century. They preserved a legendary tradition that they adopted the Sorghum varieties, called Ma-sakwa or Masawa in some areas, from the ancient population of the Sao whom they mixed with. With the crop itself, which became their hence-forth most important staple food, they introduced its techniques of culti-vation peculiar for the firgi soil (cf. below). Whereas the Kanuri are autochthonous peasants of the Chad Basin, the Shuwa immigrated into the Borno region as semi-nomadic pastoralists from the east during the 18th and early 19th centuries. It is thus obvious that they adopted a con-siderable part of the know-how concerning the conditions and the termi-nology of soils as well as the practices of land use from the Kanuri. The following list presents the indigenous names of five types of soil, which are usually differentiated by the Kanuri and the Shuwa, and a brief de-scription of their relevant characteristics (tab. 1).
This paper discusses archaeobotanical remains from the settlement mound of Kursakata, Nigeria, comprising both charred and uncharred seeds and fruits as well as charcoal. In addition, impressions of plant tempering material in potsherds were analysed. The late Stone Age and Iron Age sequence at Kursakata is date from 1000 cal. B.C. to cal. A.D. 100. DomesticatedPennisetum (pearl millet), wild Paniceae and wild rice are the most common taxa. Kernels from tree fruits were regularly found including large numbers ofVitex simplicifolia—a tree which is absent from the area today. A distinct change in plant spectra can be observed between the late Stone Age and the Iron Age. Although domesticated pearl millet was already known at the beginning of the settlement sequence of Kursakata, it only gained greater economic importance during the Iron Age. Besides farming, pastoralism and fishing, gathering of wild plants always played a major role in the subsistence strategy of the inhabitants of Kursakata. The charcoal results show that firewood was mainly collected from woodlands on the clay plains, which must have been more diverse than today. The end of the late Stone Age in the Chad Basin was presumably accompanied by the onset of drier environmental conditions from ca. 800 cal. B.C. onwards.
A pollen diagram from Oursi in Burkina Faso is compared with anthracological (charcoal analysis) results from three sites in northeast Nigeria (Konduga, Gajiganna, Lantewa). The present-day vegetation at all four sites is Sahelian or Sahelo-Sudanian and under heavy human impact. At Oursi, a closed grassland with only few trees and almost no Sudanian elements can be reconstructed for the middle Holocene. At the Nigerian sites, on the other hand, Sudanian woody plants were present during this period. We assume that the Sahel was not a uniform zone during the middle Holocene but rather a mosaic of different vegetation types according to local site conditions. In the light of these results, a simple model of latitudinally shifting vegetation zones is not applicable. Around 3000 B.P. the closed grassland at Oursi was opened by agro-pastoral activities, and at Gajiganna, plants characteristic of pasture lands can be directly related with the presence of cattle. Human impact seems to have been the dominant factor in the vegetation history of the Sahel from 3000 B.P. until today, masking possible effects of climatic change.
Late Holocene climatic changes caused a large scale regression of the Lake Chad shoreline followed by an expansion of settlements into previously unexplored territories. Numerous Final Stone Age sites of the Gajiganna Culture (1,800 to 800 b.c.) in the Lake Chad Basin (northeast Nigeria) yielded plant impressions in potsherds. The ceramics of Phase I (1,800–1,400b.c.) were mineral tempered, and plant impressions, mainly of Paniceae, were caused only by incidental inclusion. In contrast, a considerable number of the sherds from Phase II (1,500–800b.c.) were intentionally tempered with chaff derived from domesticated pearl millet (Pennisetum glaucum), wild Paniceae and wild rice species (Oryza cf. barthii
and O. cf. longistaminata). This plant spectrum suggests the exploitation of the wet wild areas, and also the cultivation of pearl millet on sandy soils. The evidence suggests that agricultural practices were established late and were introduced from elsewhere. During the time of seasonally occupied sites in Phase I, the subsistence strategy was based on herding, fishing, and gathering, while in Phase II there are signs of permanent settlements and agriculture. The evidence from the plant impressions indicates that in the Final Stone Age Gajiganna Culture around 1,000–800b.c., pearl millet became well established while the gathering of wild millets and rice was still practised.
Throughout the Holocene living conditions in the Chad basin have strongly been influenced by various transgressions and regressions of Lake Chad. In this article we concentrate on selected lake levels and climate fluctuations which had major implications on the settlement history during the later Holocene millennia. These are the ca. 287-290m-transgression which ended around 3000BP/1000 BC, the 285/286m-level which was reached several times during the last 3 millennia, and finally oscillations during the last two centuries which are recorded in travellers and colonial reports as well as modern collections of environmental data.
The reconstruction and cartographic representation of the extent of these former lakes are based on the interpretation of detailed topographic maps, satellite images, various thematic and historic maps and the evaluation of a digital elevation model.
Geographical information is then compared with archaeological and historical data and the effects of the lake level changes on the settlement and political history are evaluated. It becomes apparent that human response to environmental change is multifaceted and complex. Although certain repetitive patterns are evident throughout recorded history (12th century AD to present), the effects are very much dependent on the particular historic circumstances prevailing at the respective points in time.
Archaeobotanical evidence from archaeological sites in northeast Burkina Faso dating to the first and second
millennia AD has provided a useful insight into crop cultivation and the development of the West African savanna
landscape. Nitrogen isotopic analysis of charred pearl millet grains from the same sites now provides the
first opportunity to investigate how increased crop production and permanence of cultivated fields related to the
intensity of household waste/manure application. Nitrogen isotope values of pearl millet grains increased during
the first two millennia AD, indicating an intensification of manuring that would have enabled soil to stay fertile
for longer, reducing the agricultural footprint of shifting cultivation. This may have been advantageous as population
and settlement density increased, thereby increasing competition over land. The intensity of manure
application in the second millennium AD at sites close to the Mare d’Oursi suggests that manure was likely
sourced from outside the farming settlements, from livestock herded by nomadic pastoralists who would have
been drawn to the mare for water. This is rare evidence for specialisation of sedentary farmers and pastoralists,
demonstrating how the novel combination of fruit/seed, charcoal, faunal and isotopic evidence used in this study
can enrich our knowledge of past lifeways in West Africa.
Pits are common features at sites of the Nok Culture, which is known for its masterful terracotta sculptures and for early iron metallurgy in sub-Saharan Africa. If pits are stratified and well-dated, contained archaeological charcoal may serve as a proxy for vegetation change—especially for changes mediated by human impact. Recent investigations into charcoal samples from several pits at Pangwari, a Nok site that has been—not necessarily continuously—in use during the last 1.5 millennia BC, revealed that the taphonomy of these assemblages is not as straightforward as expected. Find distribution analysis documents that regularly only the lowermost parts of the pits are still in their original state. Later re-working of the original pit filling, erosion, and recent illicit digging for terracotta figurines challenge the interpretation of the charcoal data. Moreover, the distribution of ¹⁴C dates and of potsherds assigned to different pottery groups, as well as differences in the charcoal assemblages of some pits, hint towards divergent backfill histories. Some pits seem to have been refilled quite quickly, possibly even in a single event, while other pits might have remained open for a longer time. Additionally, pits likely were reused in later phases and the infill became mixed. For charcoal analysis, it is hence crucial to consider the backfill history of each pit based on the archaeological evidence.
Les parcs, qui manifestent une sorte de domestication de la cueillette, ménagent une large place aux productions oléifères. Dans le passé, leur importance semble avoir été plus grande encore du fait de la non-diffusion de certaines cultures aujourd'hui omniprésentes et du besoin en huiles non seulement alimentaires, mais aussi et surtout «vestimentaires ».
Cette étude aborde les rapports entre matières grasses et agro-systèmes, entre matières grasses et paysages de parcs. Elle s'interroge sur l'absence notoire dans certaines séquences géographiques, d'essences comme Vitellaria paradoxa et elle tente de reconstituer les recouvrements successifs des différentes matières grasses afin de mieux comprendre les paysages en place actuellement. Elle oppose en particulier deux parcs antithétiques, celui d'Acacia albida, représentatif d'un agro-système incluant un élevage bovin sédentaire et celui du karité, «l'arbre à beurre », illustrant un système économique sans bétail.
Elle pose aussi la question de la pérennité du témoignage privilégié que fournissent les essences oléifères, ou de celui, plus indirect, d'Acacia albida, face aux transformations qui se dessinent dans l'agriculture soudano-sahélienne.
Charcoal often retains sufficient qualitative anatomical features for the family and genus of the wood to be identified. During the charring process however, considerable and sometimes unexpected changes in quantitative characters occur, which are of particular importance to species identification and ecological wood anatomy. Comparative measurements were made using charred and uncharred trunkwood from six common southern African savanna trees. SampIes were charred for 30 minutes at either 400 or 700°C. Charcoal yield and significant quantitative changes in vessel diameter and ray cells are related both to wood anatomy and to the process of combustion. Differences observed on charring were most closely correlated with the nature and quantity of the fibres. Axial parenchyma cells expanded after charring at both temperatures.
In the last few years, archaeological investigations carried out at the mid-first millennium BC settlement site of Zilum, Nigeria, have integrated magnetic survey, a geophysical technique, as an additional source of information. Amongst other results, the magnetic survey revealed the presence of an archaeological feature that encloses the entire settlement area. Excavations show that this feature consists of a ditch. Dimensions and shape suggest that its function was to restrict access to the settlement. Although direct evidence is missing, the ditch was most probably accompanied by an earth rampart or wall, now completely decayed. Based on the available data, it seems likely that Zilum was a fortified settlement.
Charcoal samples from final Stone Age sites and stratified iron age settlement mounds in northern Burkina Faso illustrate the development of the West African savanna as a cultural landscape between 2000 BC and modern times. In the second millennium BC, plant cultivation was only a minor activity of predominantly mobile groups and did not alter the vegetation significantly. In the Iron Age, after 0 BC/AD, large settlement mounds were formed by sedentary populations, and a shifting cultivation system with fields and fallows established on the dunes. Cultivation was practiced in park savannas, an agroforestry system with protected wild fruit trees interspersed in the fields. During the first millennium AD, extensive cultivation with long fallow periods was practised. With the beginning of the second millennium AD, fallow periods became shorter and the influence of cattle herding on the vegetation increased, changing the composition of the woody vegetation. Decreasing precipitation and anthropogenic pressure eventually led to the much lower species diversity of the modern woody vegetation.
Lake Chad lies at the southern extreme of the Sahara Desert and is well known for large fluctuations in its surface area this century. Seasonal fluctuations, however, have received much less attention. This paper presents the results of two complimentary research efforts on the south-west shore of the lake. These illustrate how important both inter and intra-annual fluctuations in the level of the lake are, both in terms of their impact on the environment and in the response of the communities living on the lake shore. The paper compares a time series of the fluctuations in the level of Lake Chad as monitored by the TOPEX/POSEIDON satellite with findings from participatory research with the communities of the south-west lake shore. It shows how the communities of the lake have responded to lake-level fluctuations with their livelihood choices. These results are used to show that although vastly different in scope, a high degree of complimentarity exists between remotely-sensed information and community-based research and that they are of potentially great value to development initiatives on the shores of Lake Chad.
Aim Woody vegetation patterns in African savannas north of the equator are closely connected to human presence, but the distinctions between natural and anthropogenic landscapes have not been clear to many observers. Criteria for identifying savanna landscapes on a continuum of intensity of anthropic impact are explored.
Methods A key savanna tree species, Vitellaria paradoxa (Sapotaceae), was used as model for evaluating anthropic impact. Fruits harvested from tree populations across the species range were analysed for variation in traits valued by indigenous peoples. A simple selection index was used to scale tree populations from a hypothetical wild state to a hypothetical domesticated state. Index values were compared with trait values along climate zone gradients and evaluated in the context of indigenous savanna management practices and historical species distribution reports.
Results Trait values such as fruit size and shape, pulp sweetness, and kernel fat content show a significant influence of temperature and rainfall. At the same time, the mean values of groups of traits vary perpendicular to the general climatic zone gradient. Selection index values between Vitellaria populations vary up to sixfold, with highest values in central Burkina Faso. Comparison of present day Vitellaria distribution with historical range limits show range expansion by human migration.
Main conclusions The prevalence of major economic tree species in the savannas of Africa north of the equator is a strong indicator of human involvement in tree dispersal. This conclusion is supported by paleobotanical evidence and by recent Vitellaria range expansion as a result of human migration. The presence of high mean values of several Vitellaria fruit traits in central Burkina Faso suggests that selection for desired characteristics has occurred. The impact of indigenous savanna peoples on woody species composition and spatial distribution is probably much greater than usually thought and is the result of a deliberate strategy of altering the landscape to provide needed human resources.
Archaeological and ethnohistorical investigations were conducted in the area around the town of Ngala in Borno State, Nigeria, situated immediately south of Lake Chad. Four mounds were excavated. Comparison with data from excavations and ethnohistorical studies provided a fairly complete picture of the settlement and cultural history of that most environmentally peculiar region. It is now evident that Late Neolithic settlers established themselves around 1000 CalBC in permanent hamlets with year-round occupation and a subsistence based not only on gathering, hunting and fishing but also on cattle herding and probably the cultivation of domesticated Pennisteum. Certainly, cultivation is attested after the onset of the Early Iron Age around 500 CalBC. Although from then on we see a steady development toward further complexity with the establishment of compact villages during the middle of the first millennium CalAD and the foundation of local principalities during the fourteenth century AD it was not before the fifteenth to sixteenth centuries AD, that the mode of subsistence and the political and societal structure typical for the area today was fully developed. By then, the wider region came under control of the Borno Empire, a situation which lasted up to the early colonial days at the onset of the twentieth century.
Des recherches archéologiques et ethnohistoriques ont été conduites dans les environs de la ville de Ngala (état du Borno, Nigeria) située immédiatement au sud du lac Tchad. Quatre tertres d'habitat ont été fouillés. La comparaison des matériaux excavés avec ceux des fouilles antérieures, complétée par des analyses ethnohistoriques, a permis de reconstituer de manière assez complète l'évolution du peuplement et la succession des cultures dans cette zone qui se distingue par des conditions environnementales particulières. Il est clair aujourd'hui que les colons du Néolithique récent se sont installés, vers 1000 CalBC, dans des hameaux permanents occupés toute l'année, et que leur subsistance n'était pas uniquement basée sur la chasse, la collecte et la pêche, mais probablement aussi sur l'élevage et la culture du Pennisteum domestique. Certainement l'agriculture est attestée au début de l'Age du fer Ancien, vers 500 CalBC. A partir de ce moment, on observe certes une évolution régulière et soutenue vers plus de complexité, avec l'apparition de gros villages dans le courant du premier millénaire CalAD, et la fondation, au quatorzième siècle, de principautés locales, mais ce n'est pas avant les quinzième et seizième siècles que le mode de subsistance et la structure socio-politique qui caractérisent cette région aujourd'hui se sont véritablement mis en place. A partir de ce moment, la zone à laquelle appartient notre domaine d'étude a été intégrée dans l'empire du Bornou, une situation qui s'est maintenue jusqu'au début de la période coloniale, à l'aube du vingtième siècle.
Charcoal, fruits and seeds of woody plants have been studied from a settlement mound in the Sahel of Burkina Faso. The archaeobotanical results provide information on economy and environmental conditions at the periphery of the medieval kingdom of Songhai at around 1000 A.D. Millet (Penniselum americanum) was the basic crop, cultivated in fields in which also grew useful trees (park savannas). Besides millet, fruits of the park savanna trees and other wild woody plants were an important part of the diet. Stratigraphical changes in the charcoal diagram indicate that millet production was intensified and the park savanna system established in the course of mound formation. The charcoal results show that the vegetation around 1000 A.D. was more diverse than today, containing many Sahelo-Sudanian elements which cannot be found in the area any more. This indicates slightly higher precipitation than today but also less severe human impact.Ltude a port sur des charbons, des fruits et d'occupation du Sahel burkinab date autour de 1000 A.D. Les rsultats archobotaniques permettent une comprhension de l'conomie et des conditions environnementales en priphrie de l'empire tait la principale rcolte, cultiv dans des champs avec des arbres utiles (savane-parc). Outre le mil, les fruits des arbres de la savane-parc et d'autres plantes sauvages constituaient une part importante du rgime alimentaire. Des changements stratigraphiques dans le diagramme des charbons indiquent que la production du mil tait intensifie et le systme de la savane-parc tait tabli au cours de la formation de la butte. Ltude des charbons monte une vgtation autour de 1000 A.D., plus riche qu'aujourd'hui avec plusieurs lments sahlo-soudaniens disparus de la rgion. Cela indique des prcipitations lgrement suprieures aux actuelles mais aussi un impact humain moins svre.
. Theories concerning the factors involved in the dynamics of savannas, particularly the tree-grass interface, are reviewed. Emphasis is put on factors related to soil moisture, soil nutrients, fire and large herbivores. The distinction between external (independent) and internal (dependent, interactive) environment is discussed and it is explained how this distinction is affected by the scale of observation.
Phytoliths, amorphous silicon dioxide (SiO<SUB>2</SUB>. H<SUB>2</SUB>O), are durable and can be separated from layers where other plant remains fail like charcoal, pollen and seeds. A pit has been discovered empty of organic botanical material at the archaeological site of Zilum in NE Nigeria (600-400 cal BC). Zilum is one of several settlements of the so-called Gajiganna Complex (c. 1800-400 BC), the first food-producing society colonizing the fringes of Lake Chad. Unlike other analogous pits in the area, it was found bare of domestic refuses of any kind including charred organic (botanical) remains. An assemblage of fossil phytoliths of the family Poaceae has been separated from this pit using heavy liquid ZnBr<SUB>2</SUB>/HCl. Integration of the present results with earlier palaeoethnobotanical studies from the region is highly suggestive that this pit was used to store a Paniceae grass.
The study area and its sub-regions
- Breunig
Radiocarbon dates from archaeological sites in Northeast Nigeria
- Franke
From gathering to agricultural intensification: archaeobotanical remains from Mege, Chad Basin, NE Nigeria
- Bigga
The 8000-yer-old dugout canoe from Dufuna (NE Nigeria)
- Breunig
G(l)anz ohne Eisen: Große Siedlungen aus der Mitte des ersten Jahrtausends BC im Tschadbecken von Nordost-Nigeria
- Breunig
Masakwa farming in northeastern Nigeria
- Kirscht
Archaeozoological studies
- Linseele
Iron Age beginnings at the southwestern margins of Lake Chad
- Magnavita
The land resources of north East Nigeria
- Bawden
The later prehistory and history of northeast Nigeria
- Breunig
Prehistoric plant use and vegetation in the Nigerian Chad Basin
- Neumann
Recent archaeological finds of domesticated Sorghum bicolor in the Lake Chad region. Recent Archaeol. Finds Domest
- Magnavita
Development of Plant Food Production in the West African Savannas: Archaeobotanical Perspectives
- Neumann
Archaeological sites of the Gourma and Mékrou plains
- Petit
Natural environment and land use in the Chad Basin, NE-Nigeria
- Sturm