Modelling long-term anthropogenic erosion of a loess cover: South Downs, UK

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Abstract
There is growing archaeological evidence that erosion induced by prehistoric agricultural activities has, in many parts of Europe, greatly thinned an original thick loess cover. The evidence for this is, however, almost entirely observational and qualitative. Whether in the time available, anthropogenic activity could have produced modern thin loessial soils has not been quantitatively evaluated. This study adopts a novel modelling approach in the estimation of long-term rates of soil loss and textural modification under prehistoric and historic tillage practices. The EPIC (Erosion-Productivity Impact Calculator) model is used to simulate the effects of erosion on a hillslope in the UK South Downs from 7000 BP to the present day. Results suggest that the major period of soil loss was between 4000 and 1800 BP under conditions of gradually intensifying agriculture following permanent clearance; that land-use rather than climate appears to be the main factor influencing past erosion rates; and that a 'thin' loess cover of c. 1.2 m is a more likely initial condition at 7000 BP than a thicker cover. Despite the tentative nature of the data used to construct the land-use and climate stages and original loessial profiles, the model succeeds in reproducing the decreased thickness and increased stoniness of present-day South Downs soils. Time series of simulated erosion and change in soil stoniness appear self- consistent and broadly plausible. The methodology therefore appears promising as a tool for testing hypotheses regarding past erosion rates.