Abstract
Abstract. Water erosion on arable land can reduce soil fertility and agricultural productivity. Despite the impact of water erosion on crops, it is typically neglected in global crop yield projections. Furthermore, previous efforts to quantify global water erosion have paid little attention to the effects of field management on the magnitude of water erosion. In this study, we analyse the robustness of simulated water erosion estimates in maize and wheat fields between the years 1980 and 2010 based on daily model outputs from a global gridded version of the Environmental Policy Integrated Climate (EPIC) crop model. By using the MUSS water erosion equation and country-specific and environmental indicators determining different intensities in tillage, residue handling and cover crops, we obtained the global median water erosion rates of 7 t ha−1 a−1 in maize fields and 5 t ha−1 a−1 in wheat fields. A comparison of our simulation results with field data demonstrates an overlap of simulated and measured water erosion values for the majority of global cropland. Slope inclination and daily precipitation are key factors in determining the agreement between simulated and measured erosion values and are the most critical input parameters controlling all water erosion equations included in EPIC. The many differences between field management methods worldwide, the varying water erosion estimates from different equations and the complex distribution of cropland in mountainous regions add uncertainty to the simulation results. To reduce the uncertainties in global water erosion estimates, it is necessary to gather more data on global farming techniques to reduce the uncertainty in global land-use maps and to collect more data on soil erosion rates representing the diversity of environmental conditions where crops are grown.
Highlights
Water erosion is widely recognized as a threat to global agriculture (den Biggelaar et al, 2004; Kaiser, 2004; Panagos et al, 2018; Pimentel, 2006)
Highest water erosion is simulated in mountainous regions and regions with strong precipitation, especially in tropical climate zones
In Africa, similar areas with high water erosion values are spread around the continent and are most common at the west coast and in East Africa, including broad areas in Guinea, Sierra Leone, Liberia, Ethiopia and Madagascar
Summary
Water erosion is widely recognized as a threat to global agriculture (den Biggelaar et al, 2004; Kaiser, 2004; Panagos et al, 2018; Pimentel, 2006). High-energy precipitation, steep slopes and lack of vegetation cover intensify water erosion. The most vulnerable areas are mountainous regions, due to steep slopes; the tropics and subtropics, due to abundant high-energy precipitation; and arid regions, where precipitation events are rare but often intense and the vegetation cover is sparse. This global distribution of water erosion is indicated by suspended sediment in rivers (Walling and Webb, 1996). South America, sub-Saharan Africa, South East Asia and East Asia have been identified as the most vulnerable regions for erosion on agricultural land by several prior studies (Borrelli et al, 2017; Pimentel et al, 1995)
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