Prehistoric palaeodemographics and regional land cover change in eastern Iberia

Much attention has been placed on the drivers of vegetation change on the Iberian Peninsula. While climate plays a key role in determining the species pools within different regions and exerts a strong influence on broad vegetation patterning, the role of humans, particularly during prehistory, is less clear. The aim of this paper is to assess the influence of prehistoric population change on shaping vegetation patterns in eastern Iberia and the Balearic Islands between the start of the Neolithic and the late Bronze Age. In all, 3385 radiocarbon dates have been compiled across the study area to provide a palaeodemographic proxy (radiocarbon summed probability distributions (SPDs)). Modelled trends in palaeodemographics are compared with regional-scale vegetation patterns deduced from analysis of 30 fossil pollen sequences. The pollen sequences have been standardised with count data aggregated into contiguous 200-year time windows from 11,000 cal. yr BP to the present. Samples have been classified using cluster analysis to determine the predominant regional land cover types through the Holocene. Regional human impact indices and diversity metrics have been derived for north-east and south-east Spain and the Balearic Islands. The SPDs show characteristic boom-and-bust cycles of population growth and collapse, but there is no clear synchronism between north-east and south-east Spain other than the rise of Neolithic farming. In north-east Iberia, patterns of demographic change are strongly linked to changes in vegetation diversity and human impact indicator groups. In the south-east, increases in population throughout the Chalcolithic and early Bronze Age result in more open landscapes and increased vegetation diversity. The demographic maximum occurred early in the 3rd millennium cal. BP on the Balearic Islands and is associated with the highest levels of human impact indicator groups. The results demonstrate the importance of population change in shaping the abundance and diversity of taxa within broad climatically determined biomes.