Ongoing and emerging questions in water erosion studies

Abstract

Soil erosion is a threat to food security, especially in regions where the area of arable land is shrinking dramatically because of soil degradation. Research on soil erosion expanded progressively throughout the 20th centu\ry, although a number of unresolved problems persist despite this issue being crucial for the environment and the welfare of society. Some basic unresolved issues, including the absence of a universally accepted definition of soil erosion and disagreement about how to measure it have contributed to a degree of scientific stagnation. Accurate prediction of the response of soils to disturbance is hampered by the dependence of the erosion process on the spatial scale involved, the time lag between the disturbance and the erosion response and the short periods for which data are typically available. We argue that devoting increased attention to the following environmental, demographic, political and societal issues will reinvigorate progress in the field. (i) The relationships between on-site and off-site consequences of soil erosion need to be elucidated if the economic and environmental costs are to be adequately assessed. (ii) Effective measures for soil conservation need to focus on spatial patterns of plant cover that reduce sediment connectivity, and most importantly on the relationships between hillslopes and sediment transfer in eroded channels. (iii) The scientific community must be able to identify early warning signs of critical transitions, if irreversible soil degradation is to be prevented. (iv) Consensus needs to be reached concerning the contribution of soil erosion to the carbon cycle. (v) The consequences of climate change on erosion and sediment transport should be investigated in depth. (vi) The general society needs to perceive soil erosion as a critical matter requiring an urgent response.