Human impact on sediment dynamics — quantification and timing

Abstract

Several methods to reconstruct past land cover are available which can be roughly divided into approaches based on pollen data and approaches based on (estimates of) historical human population. In this study, the REVEALS model and non-metric multidimensional scaling (NMDS) are applied to pollen sequences obtained from multiple alluvial floodplains located in the sandy and loamy regions of northeastern Belgium, thereby obtaining the first regional (semi-)quantitative estimates of Holocene landscape openness for this area. These estimates are subsequently compared to the two most widely-used scenarios for anthropogenic land cover change (ALCC): KK10 and HYDE.In contrast with the two population-based ALCC scenarios, the pollen-based reconstructions are well in agreement and indicate considerable variability in past land cover, not only between the two regions but even between the individual catchments. This agreement implies that NMDS could serve as an alternative approach to provide insight in large amounts of pollen data in case not all required model parameters are available to run the REVEALS model. Moreover, NMDS can provide a better understanding of which taxa are related to a particular type of landscape. Taking into account such insights in the interpretation of the REVEALS model output might help to pinpoint the onset of significant human impact on the landscape more precisely. Given that alluvial sites often experienced early anthropogenic impact, including pollen data obtained from alluvial sites could not only improve the spatial coverage and accuracy of current pollen-based land cover reconstructions but could also improve our understanding of human transformation of the landscape, which can in turn contribute to an improvement of the ALCC scenarios.