Comment on “Rainfall erosivity in Europe” by Panagos et al. (Sci. Total Environ., 511, 801–814, 2015) Karl Auerswald a, ⁎, Peter Fiener b , José A. Gomez c , Gerard Govers d , John N. Quinton e , Peter Strauss f a Lehrstuhl für Grünlandlehre, Technische Universität München, 85350 Freising, Germany b Institut für Geographie, Universität Augsburg, 86159 Augsburg, Germany c Institute for Sustainable Agriculture, CSIC, Cordoba, Spain d KU Leuven, Division of Geography, Heverlee, Belgium e Lancaster Environment Centre, Lancaster University, Lancaster, UK f Federal Agency for Water Management, 3252 Petzenkirchen, Austria abstract article info Article history: Received 6 March 2015 Accepted 5 May 2015 Available online 18 June 2015 Editor: J.P. Bennett Keywords: Rain R factor Soil erosion Recently a rainfall erosivity map has been published. We show that the values of this map contain considerable bias because (i) the temporal resolution of the rain data was insufficient, which likely underestimates rain ero- sivity by about 20%, (ii) no attempt had been included to account for the different time periods that were used for different countries, which can modify rain erosivity by more than 50%, (iii) and likely precipitation data had been used instead of rain data and thus rain erosivity is overestimated in areas with significant snowfall. Fur- thermore, the seasonal distribution of rain erosivity is not provided, which does not allow using the erosivity map for erosion prediction in many cases. Although a rain erosivity map for Europe would be highly desirable, we rec- ommend using the national erosivity maps until these problems have been solved. Such maps are available for many European countries. © 2015 Elsevier B.V. All rights reserved. The Universal Soil Loss Equation USLE (Wischmeier and Smith, 1965, 1978) including its many modifications and successors like the Revised Universal Soil Loss Equation (RUSLE, Renard et al., 1991) has become the most often used model to predict sheet and rill soil erosion by rain in science. Even more importantly, it is the still only erosion model of rel- evance that is frequently used outside science for planning purposes (e.g. land reconsolidation planning, Ankenbrand and Schwertmann, 1989) or administrative purposes (e.g. in connection with the European Water Directive). In the USLE, the influence of rainfall characteristics on sheet and rill erosion is quantified as rain erosivity. Recently, Panagos et al. (2015) published a map of rain erosivity in Europe. Although such an attempt is highly desirable given the wide relevance of the USLE, the map by Panagos et al. (2015) has significant deficiencies and is therefore likely to misguide users of the USLE for five reasons: 1. For ease of application, the influence of rain erosivity on soil erosion is split within the USLE into two of the six factors that finally have to be multiplied to yield the predicted soil loss. The R factor (rain and runoff factor) quantifies the long-term mean annual erosivity at a site, while the seasonal distribution of rain erosivity (called Erosion index within the USLE, Wischmeier and Smith, 1965) has to be convoluted with the seasonally varying protection of the soil (called Soil loss ratio within the USLE) to yield the convolution integral, which is the so-called C factor (crop and cover factor). The R factor and the Erosion index are derived from the same data and both are needed simultaneously to predict soil loss. This is why usually regional estimates of the R factor also provide the seasonal Erosion index (e.g., Bollinne et al., 1979; Rogler and Schwertmann, 1981; Strauss et al., 1995; Sauerborn, 1994). Panagos et al. (2015) provide a rainfall erosivity (R) map without providing the regionally varying Erosion index. This will likely misguide many users of the USLE, especially outside science, who are not familiar with the theoretical considerations behind the USLE. In an attempt to use the R factor map they are likely to use published C factors that were derived with an Erosion index that may not be applicable at the site of interest. This is especially true for Europe where the Erosion index varies considerably within a few hundred kilometers due to the interlacing areas of Mediterranean, oceanic or continental climate that differ in the seasonal distribution of erosivity. 2. Given the long-lasting and wide relevance of the USLE and the regional character of rain erosivity, many publications on rain erosivity in Europe exist, starting with Bollinne et al. (1979) in Belgium and Science of the Total Environment 532 (2015) 849–852 ⁎ Corresponding author. E-mail address: auerswald@wzw.tum.de (K. Auerswald). http://dx.doi.org/10.1016/j.scitotenv.2015.05.019 0048-9697/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv