Abstract
Soil degradation due to erosion is connected to two serious environmental impacts: (i) on-site soil loss and (ii) off-site effects of sediment transfer through the landscape. The potential impact of soil erosion processes on biogeochemical cycles has received increasing attention in the last two decades. Properly designed modelling assumptions on effective soil loss are a key pre-requisite to improve our understanding of the magnitude of nutrients that are mobilized through soil erosion and the resultant effects. The aim of this study is to quantify the potential spatial displacement and transport of soil sediments due to water erosion at European scale. We computed long-term averages of annual soil loss and deposition rates by means of the extensively tested spatially distributed WaTEM/SEDEM model. Our findings indicate that soil loss from Europe in the riverine systems is about 15% of the estimated gross on-site erosion. The estimated sediment yield totals 0.164 ± 0.013Pgyr−1 (which corresponds to 4.62 ± 0.37Mgha−1yr−1 in the erosion area). The greatest amount of gross on-site erosion as well as soil loss to rivers occurs in the agricultural land (93.5%). By contrast, forestland and other semi-natural vegetation areas experience an overall surplus of sediments which is driven by a re-deposition of sediments eroded from agricultural land. Combining the predicted soil loss rates with the European soil organic carbon (SOC) stock, we estimate a SOC displacement by water erosion of 14.5Tg yr−1. The SOC potentially transferred to the riverine system equals to 2.2Tgyr−1 (~15%). Integrated sediment delivery-biogeochemical models need to answer the question on how carbon mineralization during detachment and transport might be balanced or even off-set by carbon sequestration due to dynamic replacement and sediment burial.
Highlights
The recognition of detrimental effects of soil erosion can be dated back to Classical Greek philosophers such as Plato and Aristotle (Runnels, 1995)
The highest model efficiency (ME) derived from the best-parameter fit is 0.38. This ME is in line with values observed by other WaTEM/ SEDEM applications (Van Rompaey et al, 2003a, 2005; Feng et al, 2010; Quijano et al, 2016)
Large-scale net soil loss and deposition modelling connected to sediment transfer and fluxes is crucial to assess holistically the impact of soil degradation across landscapes
Summary
The recognition of detrimental effects of soil erosion can be dated back to Classical Greek philosophers such as Plato and Aristotle (Runnels, 1995). The decade old discussion on erosion and carbon content has not yet brought to a unanimous opinion clearly indicating if soil erosion increases or decreases CO2 emissions through enhanced mineralization versus sediment burial (Lal, 2004; Van Oost et al, 2007). It may depend on the type of land-use and management practices if soil must be perceived as a sink or source of atmospheric CO2 (FAO ITPS, 2015)
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