Did Prehistoric Landscape Management Retard the Post-Glacial Spread of Woodland in Southwest Asia?

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Archaeological research has revealed the detailed emergence and spread of Neolithic and later farming societies in Southwest Asia. Evidence from excavated seed remains and animal bones indicates that by the Pre-Pottery Neolithic B (PPNB), c. 7000 cal BC, the main transition from foraging to farming was complete in the core region of domestication (Bar-Yosef & Belfer-Cohen 1992; Harris 1998). This on-site evidence shows how human action transformed a selected range of plants (notably cereals and pulses) and animals (sheep, goat, cattle and pig) from wild to domesticated (Zohary & Hopf 2001) On-site archaeological data provide abundant evidence for the human exploitation of many other natural resources such as wood, clay, obsidian and other stone materials; raw materials which were sometimes transported over distances of >100 km. The size and number of settlement sites also increased significantly during Neolithic/Chalcolithic times, reflecting at least an order of magnitude increase in total human population in the region from the preceding Mesolithic/Epipalaeolithic period.

Despite this wealth of archaeological data for greater human utilization of the natural environment, off-site (i.e. non-archaeological) evidence for prehistoric human impact in this region has remained elusive. Willis & Bennett (1994) highlighted the significant discrepancy in time between the arrival of Neolithic agriculture, as testified archaeologically, and the first appearance of cultural indicators in pollen diagrams from Greece and the Balkans, a time delay amounting to >2000 years. In fact, unambiguous, large-scale human impact and the creation of cultural landscapes has been inferred from East Mediterranean pollen diagrams only during Bronze Age and later times (Bottema & Woldring 1990; Eastwood et al. 1998). It has therefore been assumed that the magnitude of Neolithic-Chalcolithic agriculture was not sufficient to be registered clearly in pollen diagrams from southwest Asia.

Pre-Bronze Age environmental impacts are difficult to identify with certainty from east Mediterranean pollen records for several reasons. First, the emergence of farming communities early in the Holocene period means that a pre-Neolithic base-line `primaeval' vegetation may not have existed for comparison, unlike--for example--in northwest Europe. Consequently it is conceivable that significant human impacts began even before vegetation had completed its adjustment to the major shift in climate at the end of the last glacial period (cf. Pullar 1977). Second, many palynological indicators of cultural activity are present naturally in southwest Asia. Cerealia-type pollen, for example, which in northern Europe has been used to identify prehistoric crop husbandry (e.g. Simmons & Innes 1996), is also produced by wild cereal and other grasses in the Mediterranean region, and so does not provide a diagnostic indicator of prehistoric farming activity (Bottema 1992). Precisely because Southwest Asia was a centre of crop domestication, wild and domesticated plants cannot easily be distinguished from pollen data. Third, many fruit trees and other useful plants are not wind-pollinated, and they are consequently invisible in pollen diagrams (Woldring & Cappers 2001).

Early Holocene vegetation and climate

Pollen diagrams from southwest Asia (FIGURE 1) show that the Last Glacial Maximum, around 20,000 years ago, was marked by reduced Arboreal Pollen (AP), and that tree cover increased during the course of the last deglacial transition (van Zeist & Bottema 1991). This expansion took place earliest in the coastal montane regions of the Levant and western Turkey, where there was a clear increase in trees during Late-Glacial times (van Zeist & Bottema 1991; Kuzucuoglu & Roberts 1998). This was followed by a contraction of woodland probably coeval with the European `Younger Dryas' (GS-1) cold stage, and a second expansion during the early Holocene. …