Abstract
Over the last 8000 years the Fertile Crescent of the Near East has seen the emergence of urban agglomerations, small scale polities and large territorial empires, all of which had profound effects on settlement patterns. Computational approaches, including the use of remote sensing data, allow us to analyse these changes at unprecedented geographical and temporal scales. Here we employ these techniques to examine and compare long term trends in urbanisation, population and climate records. Maximum city size is used as a proxy for the intensity of urbanisation, whilst population trends are modelled from settlement densities in nine archaeological surveys conducted over the last 30 years across the region. These two measures are then compared with atmospheric moisture levels derived from multiple proxy analyses from two locations close to the study area, Soreq Cave in Israel and Lake Van in south-eastern Turkey, as well as wider literature. The earliest urban sites emerged during a period of relatively high atmospheric moisture levels and conform to a series of size thresholds. However, after the Early Bronze Age maximum urban size and population levels increase rapidly whilst atmospheric moisture declines. We argue that although the initial phase of urbanization may have been linked to climate conditions, we can see a definitive decoupling of climate and settlement patterns after 2000 BC. We relate this phenomenon to changes in socio-economic organisation and integration in large territorial empires. The complex relationships sustaining urban growth during this later period resulted in an increase in system fragility and ultimately impacted on the sustainability of cities in the long term.
Highlights
The rise of cities forms an enduring theme in global history [1], and of the many approaches to urban analysis, city size continues to form a key dimension [2]
We argue for a definitive decoupling of climate and settlement patterns after 2000 BC and relate this to changes in socio-economic organisation and integration in large territorial empires
The second urban cycle comprises a large number of smaller cities of the mid third millennium BC which rarely exceed 100 ha in area but again show occasional plumes above this figure (Fig 2)
Summary
The rise of cities forms an enduring theme in global history [1], and of the many approaches to urban analysis, city size continues to form a key dimension [2]. Because ancient cities were social and economic phenomena [3], and interacted with their physical environment at a variety of spatial scales [4], the analysis of temporal trends in urban development can appear bewilderingly complex. Among the many forces acting on the ancient city, climate is often regarded as significant because the provisioning of such large settlements is in part related to PLOS ONE | DOI:10.1371/journal.pone.0152563. Among the many forces acting on the ancient city, climate is often regarded as significant because the provisioning of such large settlements is in part related to PLOS ONE | DOI:10.1371/journal.pone.0152563 March 28, 2016
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