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Contenido archivado el 2024-06-18

Studying Micro-Scale Socio-Ecological Development In Marginal Zones: An Integrated Methodology

Final Report Summary - MISSED (Studying Micro-Scale Socio-Ecological Development In Marginal Zones: An Integrated Methodology)

The purpose of the MISSED project was to investigate local-scale human/environmental dynamics in arid margins, particularly the inland alluvial fans found across the desert regions of Central Asia. Because of the transitional nature of such regions, the socio-ecological balance is particularly susceptible to local environmental, hydrological or anthropogenic changes. The purpose of this Marie Curie project was to better understand the development of local human/landscape dynamics over the late Holocene in these boundary environments, and to explore their co-evolution.

Over the two year duration of this project, the researcher focused on one particular inland alluvial environment, the endorheic Murghab delta in southeastern Turkmenistan. Since at least the late 5th millennium BP, and perhaps much earlier, sedentary societies have existed within this alluvial fan. Although the best-known and by far the largest is the “Silk Road” city of Merv, archaeological surveys have revealed of thousands of sites throughout the delta. Of particular interest was the distal region of the alluvial fan, in which the delta-desert transition is more immediate, and transitional dynamics likely to be more pronounced. The primary research goals were: a) To assess the degree to which past and present micro-environments may be identified and analysed via remote sensing and geoarchaeology; b) to determine the degree to which variable and non-uniform aspects of local socio-ecological change may be identified in inland arid environments; and c) to develop qualitative socio-ecological models and transferable methodologies to understand the local co-evolution of anthropogenic and environmental processes.

The research followed two distinct but interrelated trajectories. The first of these was desk-based, focusing on interpreting present-day land-use and land-cover via integrated remote-sensing datasets. These included time-series data: including multispectral, thermal and synthetic aperture radar (SAR) imagery, as well as previously-obtained high-resolution satellite data and UAV imagery. The second research trajectory was field-based, and focused on geoarchaeological sampling of several test pits in regions of likely palaeohydrological and archaeological activity. Column samples were subject to a series of physico-chemical analyses that included Loss on Ignition, Particle Size analysis, geochemical analysis via ICP-MS/ICP-AES, and magnetic susceptibility. Thin sections were also obtained for micromorphological analysis, and 8 OSL dates were acquired.

The two-year MISSED project has yielded several significant results that are relevant not only for understanding local-scale Holocene trajectories in the Murghab delta, but also for examining desert-delta boundaries more generally. Firstly, the research provides a new and much-needed local chronology for Holocene depositional processes in the Murghab alluvial fan. The integration of these dates with the physico-chemical data from the test pits shows that while regional paleoclimactic trends, such as a middle Holocene moist period, and a period of increased aridization after 4000 BP can be broadly supported, there are significant indicators of variability at the sub-regional and local levels that can shed light on human/environmental interactions in the distal margin. The geoarchaeological evidence shows that the development of the distal landscape represented a long-term succession of palaeohydrographic and geomorphological processes shaped by ongoing alluvial-aeolian interaction throughout the late Holocene. The human geographic landscape that developed from the late 5th millennium BP onward did so within a broader palaeogeographic context in which the expansion of the fluvial system, likely during a period of increased moisture throughout much of the later 5th millennium BP, facilitated widespread human occupation and exploitation of portions of the distal fan. Discontinuous areas of soil development in close proximity to widespread pottery scatters suggest that cultivation of channeled regions, as well as exploitation of unconfined water resources (e.g. pools, local wetlands) occurred towards the end of the 5th millennium BP. Increased evidence of sand encroachment, both in particle-size data and in micromorphological thin sections, suggest that elements of desertification were ongoing processes, although intensification likely occurred significantly later.

Locally, the geoarchaeological data from this study suggest that even over small distances of a few dozen meters, individuals and groups would have been able to exploit a varied landscape of channels, wetlands, takyrs (poorly-drained clay-pans) and dunes. Fluvial and aeolian processes served as feedback loops in which active hydrological activity tended to mitigate localized sand encroachment, while areas that were less hydrologically active were more susceptible to aeolian activity. This complex distal landscape fostered varied mechanisms of land-use and resource exploitation, in which the channelized river system provided the primary arteries for significant occupation, while non-channelized features such as pools, ephemeral lakes and wetlands offered local micro-environments that could be exploited for agricultural and pastoral activity.

While these mechanisms apply to the Murghab landscape, they also offer ways of understanding inland alluvial fans more generally. The continual interplay of fluvial and aeolian processes both fostered and degraded various local resources. Adaptation to changing local resource availability served to sustain some micro-environments while destabilizing others, contributing an anthropogenic component to an already changing landscape. These anthropogenic practices resulted in additional pressures to the human/landscape balance, which may have included land clearance, soil degradation and erosion that exacerbated extant natural processes of sand encroachment, desiccation of channels and salinization.

Methodologically, the research showed that the integration of remote-sensing data with geoarchaeological analysis can help to trace the depositional history of the landscape, which is essential in understanding human/environmental trajectories. While there was no clear direct correlation between deep subsurface stratigraphy (beneath about 20cm) and observable spectral signatures of present-day landcover, due to complex depositional and deflationary processes, satellite imagery can provide a useful record not only of the present-day landscape, but also of recent historical trajectories on the order of several decades. Access to CORONA and LANDSAT data, for example, helped to trace the progression of agricultural development and modern canal construction, systems which often exploit relict watercourses. Multi-temporal, and particularly thermal data, were particularly useful in identifying areas of active and relict hydrology. In this sense, both single-scene thermal data, as well as derived images such as multi-temporal variance images, were useful aids in identifying relict watercourses in regions of low topographic variability or visual obstruction. Additionally, SAR datasets show promise in identifying water-collection regions on takyr surfaces, which provide some evidence of the surface structure of these landforms. These have strong archaeological relevance, as they have been exploited for centuries by pastoralists, and, as the geoarchaeological evidence from this research has shown, may indicate areas of occupation or agricultural exploitation. Additionally, they can provide strong clues to the development of the palaeohydrographic system.

Ultimately, this Marie Curie project has provided new perspectives on delta-desert margins environments. By focusing on landscape variability and non-uniformity at the local level, we can better understand these endorheic deltas as agents of change in their own right, dynamic regions that facilitate creative and adaptive approaches to land use and exploitation, in the face of both constant and changing threats to the socio-ecological balance between people and landscapes. Ultimately, these arid-zone endorheic deltas, and the communities that inhabited, exploited and changed these landscapes, represent a coalescence of environmental and anthropogenic processes whose mutual influence was magnified in the transitional alluvial margin.

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