* This article appeared in Issue #3 of Tvergastein. Due to the extensive footnotes, the full bibliography was not included in the published edition. It is reproduced in fully cited form here.
Historical Ecology of Adaptations to Climate and Environmental Change, ca, 12,000 BP-AD 1860
This article illustrates how prehistoric pastoralists in the Horn of Africa adapted to climatic and environmental changes. The article uses archaeological evidence to understand how domestication of livestock enabled these nomadic bands to improve their food sources, develop organization, and use mobility to respond to changing environmental conditions. The iconography of their rock art left behind information about their adaptive mechanisms to environmental change. The livestock they domesticated and depicted in the rock art exemplify choices based on the adaptive capacities of various species, while the chronological sequences of their introduction into local habitats depict economic transformation. From this distant past, we can make inferences about societal adaptive strategies. Before proceeding, we need some clarity on the terms historical ecology and climate and environmental change adaptation. I adopt Bruce Winterhalder’s (1994: 18) definition of ‘historical ecology’. He suggests that although the concept might have a variety of meanings and refers to different ideas, it can be summed up as “a commitment to certain theoretical principles, a methodology or a form of investigation…within a framework provided by a certain set of concepts”. This description makes the concept interdisciplinary while the historical component describes the “chronological accounts of selected events”. The ecology component refers to relations between organisms (we have used rock art pastoralists) and their environments within the context of time and space. The term ‘climate change adaptation’ is defined in various ways, but we will adopt a simplified form, referring to responses to the dynamics of environmental conditions over lengthy periods that fluctuated from one stable form to another. Adaptation is a responsive action that individuals and communities undertake to protect their livelihoods over time. Adaptation could be successful if the system of production is made sustainable through structural and behavioral changes in response to long-term climate change.
We analyze the complex relationships between society and the environment at historical and geographical scales. This is despite the use of scattered sources, which Bethwell A. Ogot warns against, claiming “that uses [of] fragmented sources would leave voids”. Addressing the gaps or voids would not make it any easier for historical ecologists to investigate how societies adapted to climate change, other than by presenting a synthesis in order to make rational deductions about the mechanisms of adaptation. We will draw on proximate environmental indicators and rock art as the methods for reading climate and environmental change to learn about human behavior imbued with the use of space, time and knowledge as functional adaptive mechanisms. We will show that the survival of prehistoric pastoralists during the long and fluctuating Holocene climate (ca, 12,000 BP) was a reflection of their successful adaptation mechanisms. We will also show how the climate shifted from a wet to a dry phase, influencing corresponding shifts in vegetation cover, and investigate environmental desiccation and corresponding adaptations undertaken by societies. We consider regional connectivity in terms of sub-continental and regional scale movements of Neolithic pastoralists whose rock art depicts the domestication and selection of better adapted livestock species. Adaptive mechanisms are presented in terms of the praxis of time, space and knowledge. We ascertain the processes by which societies created social landscapes, thus leaving their ‘footprints’ across time. Here, our use of the term ‘adaptive strategies’ (or ‘adaptation’), provides us with “an interpretive tool for pursuing the intricacies [of responses to climate change] in space and time”. We have used the Horn of Africa as a regional case study. The article is divided into seven sections. The first section introduces the geographical scope; in the second, climatic and environmental changes are examined. The third examines impacts of climatic change on the environment. The fourth section dwells on the evolution of rock art pastoralists; the fifth considers regional level migrations by the rock art pastoralists. In the sixth section the article uses the rock art styles to present analysis of pastoralists’ movements, while in the seventh, it presents the analysis of adaptive mechanisms in the use of space, time and knowledge.
The Horn of Africa serves as a laboratory for the study of climate change adaptations. In this region, climate events have had a major influence on the biological activities and local economies of the pastoralists and other societies for several centuries. The physical diversity of landscapes and the ancient history of human activities provide us with evidence of regional-scale human adaptations. Geographically, the Horn of Africa lacks ‘precise boundaries’ but in this article, it refers to the region encompassing Somalia, Djibouti, Ethiopia, Eritrea and northern Kenya. Climatically, the Horn comprises the central Ethiopian highlands, the lowlands, coastal plateaus, and maritime coastal zones, making it a region of ecological diversity. The central Ethiopian highland is the hydraulic catchment area for the whole region and its patterns of rainfall enable an understanding of the climate history of the region. The area is the source of major drainage networks, the main drainage lines being the Blue Nile, the Omo, the Hawash, the Webbi Shebelle, Juba and Daua Rivers (Fig. 1). Important geographic features that have contributed to the investigation of historic climate changes are the Great East African Rift Valley lakes.
The hot deserts of the coastal plains, and the semi-desert of the lowlands inhabited by multi-cultural acephalous (non-hierarchical) societies such as nomads, have had significant impacts on the social and political landscapes of the region. Today, the semi-desert lowlands are home to between 26 and 30 percent of the total population of the Horn of Africa. The pastoralists combine different ecological systems and landscapes in their seasonal livestock grazing movements, preferring particular ecosystems for grazing by different types of livestock during the wet or the dry season. “The key was their adjustment to the [rainfall distribution which is] the primary limiting factor of production”. In the hot lowlands, the high spatial and temporal variation in vegetation production induces mobility in nomadic herds in search of grazing and water. Human adaptations to improve herd survival did not only result in the diversification of livestock species – which varied from thirst tolerant to less tolerant species – but also the application of mobility as a strategy to deal with local droughts. Thus, in terms of environmental drivers that have shaped human behavior and social memory, the landscapes in the Horn of Africa could be considered to be a historical construct which has left a “visible imprint of past human agency”. The historical ecology of the Horn of Africa has not been uniform over time; rather the environmental and human history has been punctuated by climatic episodes − periods of shocks, separated by long intervals of stability.
Climatic and environmental changes
Climate fluctuations during the Holocene were a global phenomenon. Our interest is in understanding how these fluctuations contributed to environmental changes and human responses. As Bryson and Padock imply, a shift in climate stimulates varied adaptive techniques. In the region of the Horn of Africa, both the highlands and the lowlands experienced climatic fluctuations. It is possible that during the early phase of the wet Holocene climate, the highlands were too cold for human settlement. Finnevan reports: “The …wet phase was accompanied by a glacial retreat” from the highlands in both Ethiopia and East Africa. Between 12,000 and 5,000 years ago snow retreat resulted in a rise in the levels of the Ethiopian and the East African Rift Valley lakes. At the regional level, the fluctuation in the East African Rift Valley lakes was synchronized, suggesting close links between changes in lake levels and regional climate. The timing of the changes in lake levels correlates with the changing flood patterns of the Nile River. The link is not between the Nile and the East African lakes, but with the region-wide climate fluctuations.
In East Africa, during the full Holocene period from around 10000 through 6000 BP, the high water levels in the Rift Valley lakes did not allow human settlement in the moist environments. The wet and the dry phases alternated between 4450 BP and 2700 BP, with lake levels dropping, followed by recession of the sub-humid vegetation towards arid conditions in the lowlands and the retreat of forest cover in higher elevations. From the Afar region of Ethiopia, lakebed changes depict the different phases of the paleoclimate. Grove, referring to carbon dating of the sediment cores of the lakes (i.e. Shala, Abiyata and Langano), confirms higher lake levels around 9200 BP, which retreated to the present levels by 4000 BP. The decline in the lake levels is an indication that climate conditions had shifted to a dry phase ca. 5000 BP. We draw two conclusions based on this evidence. First, the lake levels alternated between the wet and drier climates. Second, the changes towards the present conditions of the lakes were characterized by long unbroken periods of aridity. The climate change had major impacts on environmental changes.
Impact of climate change on the environment
Palynologic studies (i.e. pollen studies) enable one to draw inferences about how changes in lake levels reflect changes in the environment and in turn the types of economic activities pursued by inhabitants. The pollen grains that serve as environmental fingerprints varied according to local conditions, while at regional level they displayed physiognomic changes in response to changes in the climate. However, attributing the pollen data to either local land use or climate change might require careful consideration. This caution aside, the use of pollen as a reflection of ecological changes remains valid for collecting information about local and regional level environmental changes caused by past climate change. The pollen describes “vegetation history” in relation to changes in climate and human land use. The changes might be local or regional, according to the patterns of pollen deposits. Each phase of vegetation change was dynamic, increasing the “significance of various genera”, which characterized the particular climate phase.
In the northern Ethiopian highlands, the climate shifts resulted in the retreat of humid forest covers “giving ground to expanding grasslands”. In the northern region of Kenya and the extreme northern parts of the Horn of Africa, the wet climate encouraged the growth of savannah woodlands between 9000 and 6700 BP and wooded-grassland savannahs by about 6000 BP, which encouraged the early herders to introduce goats. In southeastern Ethiopia, pollen analysis from the Arsi and Bale highlands showed decreases in pollen taxa between ca. 600 and 300-200 BP in response to reduced temperatures, providing evidence of strong background effects from climate changes. The drier phase of the Holocene climate prompted the Neolithic pastoral cultures to synchronously adjust their systems of land use. Rather than subduing their land use systems, the temporality and spatiality of the environmental variations induced adaptive mobility, a critical survival mechanism for the herds. As aridity increased, there were corresponding changes in vegetation adapted to arid conditions. Archaeological records show the impacts of human subsistence mechanisms such as foraging and livestock grazing in the form of an increase in the use of fires during the humid phase between ca. 6600 and ca. 1900 BP.
The period referred to as the Medieval Warm Period (MWP) (AD 1000 to 1270) was followed by periods of persistent aridity suggesting that the environments in the Horn of Africa could have been much drier than they have been during the present day. Rainfall fluctuated between the seventh and eighth centuries, followed by increases in the tenth and eleventh centuries and a decline by the thirteenth and fourteenth centuries. The drier climates were likely to have reduced pastoralists’ utilization of some of the areas, forcing the population to disperse. Aridity created scarcity in water and pasture, to which the pastoralists responded by adopting more drought resistant species of livestock. The dry conditions prevailed from AD 1700 to AD 1750. This was the period when the western regions of East Africa experienced major droughts. Aridity became widespread between 1750 and 1860. The changes had dramatic effects on the evolution of the rock art pastoralists.
The evolution of rock art pastoralists
Evidence from rock shelters is available from around 9000 BP when Neolithic pastoralists had expanded “and progressively assimilated more and more of their neighbouring gathering-hunter peoples into their societies”. The Horn of Africa might not be the origin of pastoralism, but the emergence of this lifestyle change in the region is attributable to climate change that forced societies to abandon foraging habits for livestock herding. The Neolithic herders arrived from the Sahara. The period between 5000 BP and 3000 BP represents the mid-Holocene, when aridity induced migrations of prehistoric pastoralists into the Horn of Africa. In the East African highlands pastoralism appeared abruptly around 3000 BP. The appearance of the pastoral population in the highlands might suggest an adaptive response to aridity in the lowlands where resource pressure could have forced some of the less adapted populations to move into wetter ecosystems. During the wetter phase of the climate, pastoral grazing lands expanded, allowing population dispersal, whereas during the dry climate pastoral land use was concentrated around key resources, as depicted in rock art.
Rock art is an important source of scientific information as a proxy for the human conceptualization of nature and as a framework of social expressions about ancient systems of production, social beliefs and knowledge. “Rock artist’s mental space [is] framed in an iconographic language”. Representations of different landscapes and social and economic scenes serve as ‘images’ of ‘territorial markers’. Population aggregation and organization required ritual spaces across territories. As Tilley suggests, “the meanings of space always involve [a subjective] dimension and cannot be understood apart from the symbolically constructed life worlds of social actors”. In this case, the actors used symbolic images of livestock to tell stories about their beliefs, values and the environmental changes they were experiencing.
During the Neolithic period called Bovidian, the styles of the rock art enable various interpretations based on the depiction of livestock species such as ovids (goats) and capris (sheep) and Bovin (cattle). By about 8000 BP, the depictions in the rock art were mainly of ovicaprids and cattle. The rock artists were predominantly concerned with the sources of their food during each period. Thus, the shift from the Paleolithic phase, which represented the hunter foragers, to Neolithic developments, which represented pastoralists, show shifts in food sources and society responses to climate and environmental changes. The domestication of Bos primigenius (primitive cow) expanded into the Nile valley about 7000 BP; this was the ancestor of the cattle breeds Bos taurus (the humpless long horned) and Bos indicus (the humped short horned zebu). Bos taurus was common during the humid phase of the climate, while Bos indicus became prominent with increased aridity. The depictions show that the rock art serves as a slow cinematic sequence of pastoral evolution to climate change, even when data from a single site is scrutinized. In particular, the gradual disappearance of Bos taurus and the popularity of Bos indicus in rock art sites strongly imply environmental adaptation since Bos indicus had better thirst tolerance than its predecessor. The camel was introduced later than the bovids during periods of increased aridity.  From the rock art across the region archaeologists have pieced together the regional migration patterns of the rock art pastoralists.
Regional migrations by the rock art pastoralists
From rock art and other archaeological evidence, we see that pastoralism was introduced into the Atbara valley at the end of 4000 BP. Desiccation and droughts triggered migrations through Nubia (in present day Sudan) into Ethiopia. The introduction of cattle (Bos) into the Ethiopian highlands spread into the lowlands of Afar, down the Red Sea coast. This route represents not only one phase of migration, but a series of migrations reflecting changes in ecology and pastoralists’ adaptations to mobility. Amanuel Beyin and John Shea state:
Beginning around 25000 [BP], pastoralists and agro-pastoralists from the Butan region east of the Nile began to move further east, eventually establishing large villages along the Gasha River…Dependent on cattle, goats, and sheep and perhaps cereals as well as wild game and plant foods, they also migrated into the Red Sea hills…The Gash group…continued their movements to the east, soon occupying the entire Sudan-Eritrean borderland, including Agordat. Farming and herding were the main subsistence activities, except for more environmentally marginal lands…The Agordat communities…could have played a very important role in the region as the social, economic, and political conduits between the polities of Eastern Sudan and the Nile valley, and the increasingly more complex socio-political systems emerging in the Eritrean/Ethiopian highlands such as the ‘pre-Axumites’ and the Ancient Ona.
On the Asmara plateau archaeologists found fauna remains indicating some level of specialization by pastoralists; in some sites there were cattle remains, while in others sheep and goat remains were found. The “patterns in archaeology appear to be deliberate herd management techniques.” In the Eritrean lowlands that served as a major centre of pastoral rock art dispersal, climate adaptations were impractical without the accompanying development of socio-economic and political complexities in the emerging societies that combined a variety of production systems. About 300 BP, the communities of the Ancient Ona in the Greater Asmara that earlier practiced a mixed agriculture disappeared, but from archaeological evidence, it is uncertain if abandonment and its drivers were comparable across the region. Yet that abandonment might have been followed by societal transformations and increased diversity in their economies. It was quite possible that by the 1st millennium BP the pastoralists pursued different economies linked by trade and labor exchanges with the highlands. From there on different pathways might have become available as the societies differentiated into distinct cultural groups.
By the beginning of the Christian era, there is evidence that the Axumites were in contact with the Beja nomads, through trade and conflicts. Enslavement of the nomads may have been the purpose of the raids conducted by the Axumite Empire. By about 700 AD, the Axumites had herds of “long- and short-horn cattle, sheep and goats” and trade with the nomads in the lowlands. The nomads in the lowlands controlled the import of metallurgy ores and other imports from across the seas into the Axumite kingdom. The relationship between the highland agro-pastoralists and the lowland pastoralists was therefore not necessarily always one of conflict, but rather, mutual relations shared through trade networks.
Pastoralism was already the dominant form of subsistence agriculture by 3000 BP in the western lowlands of Ethiopia, and expanded into the rest of the Horn of Africa by 2000 BP. At that time, aridity forced the pastoralists to move into the highlands on the northern and eastern Ethiopian plateaux. Evidence adduced from rock art shows that environmental disasters triggered population movements in order to seek better pastures and water for livestock. Considering that “a year is judged good or bad depending on the amount of rainfall and when it occurs,” mobility becomes a necessity of life. The populations were able to adjust to minor crises, while disasters such as climate fluctuations caused major disruptions to their existing adaptive strategies. Thus, the links between climate change and the distribution of pastoralism remain a relevant means of tracking environmental change. Regarding responses to environmental desiccation by rock art pastoralists, Brandt and Carder had the following to say:
…the desiccation of the northern African environments elicited the migration of pastoralists and/or diffusion of their products into the Horn by c. 500-4000 BP. We predict that, given the pronounced environmental dichotomy [i.e. the highlands and the lowlands] in the Horn, pastoralists would rapidly establish a bipolar mobility pattern…from the highland pastures to the [lowland] pastures. 
The adaptations to the variable climate were by multi-species livestock comprising browsers and grazers. We are uncertain how social stratifications and different pastoralist identities emerged. It was possible that by the late Holocene the pastoral societies of the Horn of Africa were beginning to build separate societies demonstrating territorial behavior. Based on the nature and location of the resources, groups might have fashioned geographically distributed territorial systems, within which they dispersed. Our knowledge is from the iconography of the rock art, from which influences of climate and environmental changes can be interpreted.
The rock art evidence shows two important developments. The first development is a link between different types of pastoral existence, perhaps alluding to cultural variations, which meant that the artists were able to vary their messages in the rock art. The second development is evidence of environmental change that might have brought different groups into the same area, thus making the transfusion of knowledge possible. The most important issue for us to consider is whether the appearance of different styles of rock art and the clustering of sites might enable inferences about intra- and inter-regional relations. According to Brandt and Carder, common styles such as the fusion of limbs and “variations in bovine torsos and horns may reflect the maintenance of alliance networks at an inter-regional scale while emphasizing intra-regional socio-economic participation”. The density of the rock art sites in different locations also suggest “settlement size, density of material culture” and duration of occupation and emergence of territoriality.
The various styles of rock art are depictions of human behavior and beliefs. The spread of the animal breed types was from the Horn of Africa to eastern Africa. Following the desiccation of the environment in the Horn between ca. 3000 and 2000 BP, the short horn zebu depicted in the rock art were widely distributed on the western Eritrean plateau and along the coast by the 2nd millennium BP. The type of rock art of this period has the iconographic or style name ‘sorre-Hamakiya.’ Teka reports that the “artistic style of ancient rock art provides the basis for recognizing a particular cultural-historical tradition”. In the common style of rock art referred to as ‘Ethiopian-Arabian’, the main features are “the depiction of humpless bovine in profile with forelimbs and the hind limbs each merged into one thick line”. In rock art caves on the Ethiopia-Sudan border, depictions include rainmaking rituals, showing the complexity of inter-regional relations between different sites as well as expression of shared cultures and differences.  Records from eastern Ethiopia and the northern parts of the Horn (the present day Somaliland) show that the rock art depicted domestic species with different art styles. In Somaliland, the rock shelter called Damaline has polychrome paintings depicting sheep, wildlife, snakes, turtles and human figures with arrows. In the rock art in the Gudka Hardhka caves in northern Somaliland, the iconographic representation of a camel confirms the phenomenon of increased aridity. Evidence from archaeological works elsewhere in Eastern Africa shows that the prehistoric pastoral economies had “some resemblance to that of the present inhabitants”. In the eastern Lake Turkana area, depictions in the “middle to the third millennium [BP]” show the presence of both ovicaprids and cattle, but the camel appeared only later. These pastoralists built stone enclosures to protect their livestock in the plains of the Chalbi basin and expanded southwards into the East African Rift valley due to threats by epizootics. Comparisons of the depictions across the region have yielded evidence of inter-regional relationships. The environmental and geographical locations, and therefore spaces, that connected communities, influenced their art, providing evidence of the diffusion of knowledge towards thirst tolerant livestock species.
The pastoralist communities diversified their livestock species as well as showing social transformation with the emergence of ‘resource ownerships’ as aridity induced resource scarcity with a possibility of increased competition in comparison to when the environment was wetter. Thus, the relationship between climate change and adaptation by herding communities was in the development of social institutions that ensured access to the vast drylands for grazing and built relationships with others to negotiate access to forage and water sources along their migratory trajectories. The rock art sites might reflect functional linkages with other areas, which had new key resources such as water, or resting places where pastoralists had time to express their interests and describe events around them. The art might also reflect different pastoral cultures − each identified with the livestock species they represented in their drawings − cattle pastoralists were predisposed towards cattle, while those managing mixed herds represented cattle, sheep, goats and camels in their rock art. The species preferred in the representations would in turn describe mobility patterns.  The overall impression is that there were two processes at work: pastoral mobility and diversification of livestock species, with both processes implying environmental desiccation.
The praxis of time, space and knowledge: mechanism of adaptations
We are interested in understanding how the pastoralists in earlier centuries influenced the environment within the context of climate and environmental change. How do we know what the ancient landscapes looked like and how the nomads responded to landscape changes? The question is difficult to answer considering that “[i]t is extremely difficult to reconstruct the full ecological trajectory of natural communities, and specifically, how [landscapes] have accommodated both the intrinsic variability of [bioclimatic and the long-term influences of human activity]… over the course of time.” This being so, the continuous use of the same environment by the contemporary population would have had a profound influence on the dynamics of the landscapes concerned. For the herders the past and the present landscapes are contextual both in terms of their social, historical and ecological significances. Social relations across space are the subject of a political ecology that describes the interactions between society and the environment at varied scales. Knowledge of nature expresses long-term memory of environmental changes. The knowledge of landscape as an ecological and ethnographic source presents analytical profiles of how past memories may be explained in the present.
In our interpretation of pastoralists’ historical adaptations, we have relied solely on non-chronological material in relation to changes in social behavior and memory. Nevertheless, we are obliged to work retrospectively by considering the knowledge of contemporary pastoralists in terms of the way they divide space and time according to management strategies for different livestock species. The divisions correspond with variable rainfall: the wet season being a period of plenty, and the dry and hot season being a period of scarcity. The diversity of landscapes during the annual grazing cycle optimizes the use of space and time in relation to environmental change. To attempt to understand this interplay of space, time and knowledge, we apply the social theory of praxis.
When considering praxis from the perspective of environmental change, there are multiple facets of actions and reactions. Climate change influences the environment and the society, while the society in turn influences the quality of environmental change through regular uses. We may also view environmental change in terms of “ecological praxis,” which considers the scale of use and subsequent changes in the environment. The scale refers to the extent of land units that pastoralists consider as resources that they may utilize for watering and grazing, which can be at local or regional levels. We now discuss the praxis of landscapes from two additional perspectives, the first in terms of spatial variations and knowledge systems that pastoralists require to utilize resources, and the second focusing on changes in the quality of environment that influences pastoralists’ responses.
The concept of time in this discussion is not necessarily a chronological representation of events as variously mentioned, but rather, portrays a temporal framework for exploitation of landscape resources by pastoralists. Space, in relation to prehistoric pastoralists, refers to the territories they controlled and exploited. The territories had imaginary borders across which different groups negotiated relationships. ‘Spaces’ might refer to settlements, ritual sites, grazing neighbourhoods or restricted lands preserved for dry year grazing. When combined, these concepts put the analysis of the space-time continuum into proper perspective. At geographical scales, the interaction between people and their environment describes how societies moved across space over time.
We seek to understand how people in the past, similar to those in the present, used space and perceived changes induced by either human activities or by changes in climate. In analyzing the praxis of environmental change, we might therefore examine multifarious situations that require deciphering of the complexity of human and environmental relations. The analytical approach to this challenge is not straightforward, considering that our knowledge of prehistoric pastoralists, beyond their rock art representations, is meager. The transformation from prehistoric to modern day pastoral groups and their identity shifts, as well as physical drifting across space and time, remain a matter of generalization. By expanding the spatial-time approach in terms of “the active quality of space” and extending the use of the concept to “the notion of territoriality [and], migrations,” important relationships between environmental and climate change and pastoralist adaptations can be recognized. The environment itself serves as “an historical document” so that the past can be used to make inferences about the present, an example being how societies adapt through a continuous process by which specialized and non-specialized pastoral groups (i.e. in terms of the species of livestock species they manage) respond to “new conditions.”
As far as pastoralists are concerned, the praxis of environmental change is real as well as symbolic. It is an abstraction in terms of different aspects of nature, in the form of both resources and climate change, which influence human behavior. Nomads perceive the resources provided by nature as being dependent upon two spheres of life: the physical land (i.e. the earth) and the supernatural (i.e. God). These two spheres influence how pastoralists behave and relate to the environment. The ‘earth’ produces the resources that the livestock and humans utilize, while ‘God makes resources grow’. Metaphorically, the two concepts represent landscape and climate. Nature is variable and the productivity of nature is dependent upon variation in the climate. The physical quality of landscapes influences productivity. The nomads depend on the interaction of the two in order for them to reap the benefits of nature’s variability, which they achieve by means of mobility. Pastoralists’ land use is however not ad hoc but relies on comprehensive knowledge of landscape change.
Landscapes provide traces of the historical past and therefore transcend present uses by being located in “a larger spatial” context and reveal the footprints of past human activities in terms of settlement patterns of population expansion or collapse. The historical settlement patterns transform societies’ perceptions of individual landscapes in terms of “materialized histories of decision making”, thus serving as ‘libraries’ of past environmental change that illustrate the ordering of past ecological events. The history of change therefore needs to be examined by comprehending “landscape and history,” giving rise to the term “inscription of landscape” which influences the way landscape is comprehended and interpreted. For a rock art herder, landscape identity is in terms of familiarity with individual patches from past uses, while landmark features such as a rock, a hill, a dry valley, an old tree or other shapes characterize the particular landscape. Of course, the herder’s landscapes are not mobile, but they do shift in terms of the resources they produce during different seasons. What is crucially important is the way herders interpret the changes such as shifts from grassland to bush lands.
In reconstructing historical environmental changes, we therefore consider how landscapes are “connected to past environmental memory.” We will not attempt to be more specific about the places where changes occurred, or its influence on economic relations amongst local populations, such as when the vegetation shifts from grasslands to bush lands, creating shifts in patterns of land use, with populations that managed browsers moving in and the populations managing grazers moving out. We acknowledge the common vision of seeking suitable grazing lands, whether in the past or the present. We can examine this by varying the analysis from one driven by perturbations of the environment (i.e. climate change) to one in which human overexploitation became a persistent problem as we reach the nineteenth century level of knowledge of environmental change. The challenge is to balance the narrative of adapting to environmental uncertainties, against the counter narrative in which pastoralists are destructive agents. The latter argument ignores the fact that adaptability requires regulated environmental exploitation. These varied arguments have important implications on the interpretations of historical ecology of adaptations to climate and environmental changes in the Horn of Africa by the rock art pastoralists.
 Professor Gufu Oba teaches at the Department of International Environmental and Development Studies (Noragric), Norwegian University of Life Sciences, Ås, E-mail: firstname.lastname@example.org. He is the author of numerous peer reviewed articles on ecology, Environmental history and Pastoralism. His book, “Nomads in the shadows of Empires” (in press with BRILL International) and “Surviving climate and Environmental Change in the Horn of Africa” (forthcoming, Palgrave Macmillan) are contributions to the regional studies.
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