Tolerable Versus Actual Soil Erosion Rates in Europe

Erosion is a major threat to soil resources in Europe, and may impair their ability to deliver a range of ecosystem goods and services. This is reflected by the European Commission¿s Thematic Strategy for Soil Protection, which recommends an indicator-based approach for monitoring soil erosion. Defined baseline and threshold values are essential for the evaluation of soil monitoring data. Therefore, accurate spatial data on both soil loss and soil genesis are required, especially in the light of predicted changes in climate patterns, notably frequency, seasonal distribution and intensity of precipitation. Rates of soil loss have been measured, modelled or inferred for most types of soil erosion in a variety of landscapes, by studies across the spectrum of the Earth sciences. Natural rates of soil formation can be used as a basis for setting tolerable soil erosion rates. Soil formation rates have been measured directly and indirectly, and have been inferred by modelling, for mineral weathering as well as dust deposition. This paper reviews the concept of tolerable soil erosion and summarizes current knowledge on rates of soil formation, which are then compared to rates of soil erosion by known erosion types, for assessment of soil erosion monitoring at the European scale. A modified definition of tolerable soil erosion is proposed as ¿any actual soil erosion rate at which a deterioration or loss of one or more soil functions does not occur, actual soil erosion being 'the total amount of soil lost by all recognised erosion types'. Even when including dust deposition in soil formation rates, the upper limit of tolerable soil erosion, as equal to soil formation, is ca. 1.0 t ha-1 yr-1. Scope for spatio-temporal differentiation of tolerable soil erosion rates below this upper limit is suggested by considering (components of) relevant soil functions. Reported rates of actual soil erosion vary much more than those for soil formation. This can be explained by soil formation rates being influenced by humans to a relatively small degree, in contrast to soil erosion rates, which are mostly human-induced. Actual soil erosion rates for tilled, arable land in Europe are, on average, 3-39 times greater than the upper limit of tolerable soil erosion, accepting substantial spatio-temporal variation. This review proposes a framework for assessing soil erosion and highlights the scientific areas where more research is needed for successful implementation of an effective European soil monitoring system.JRC.H.7-Land management and natural hazard