Early Holocene slope erosion in the Scheldt basin (Belgium): Naturally and/or human induced?

Abstract

The last decade increasing evidence of soil erosion by sediment run-off predating agriculture has been found in different areas of west and central Europe. A central discussion is whether pre-agricultural erosion was triggered by vegetational disturbances caused by hunter-gatherer activities (trampling, controlled forest fires) or natural processes (e.g. climatic anomalies, wildfires, wind-throws). This paper contributes to this discussion using data recently gathered during archaeological excavations of a levee, within the floodplain of the River Scheldt in NW Belgium, occupied by hunter-gatherers during the Early Holocene. These excavations revealed the presence of a ca. 40 cm thick slope deposit, which was radiocarbon dated to the late Preboreal and 1st half of the Boreal. A high-resolution, multi-proxy analysis of this deposit demonstrates a close correlation between the type of vegetation, forest fires and erosion intensity. It is concluded that repeated burning of pine-dominated forests was most likely the main trigger. Furthermore, this study provides strong evidence against an anthropogenic origin of these Early Holocene fires as burning and slope erosion already started long before prehistoric hunter-gatherers occupied the levee top and the Scheldt basin. Furthermore, this study demonstrates that pre-agricultural slope erosion was not limited to hilly regions with pronounced topography but also occurred in lowland regions with subtle topographical gradients.