Wind and water erosion are fundamental drivers of earth surface dynamics. Projected increases in both drought frequency and intense precipitation events are likely to alter land-surface dynamics through differential changes in dust emissions, water-driven sediment production, and soil degradation associated with wind and water erosion. Although wind and water erosion can be of comparable magnitude and can occur at the same location under similar time scales, rates of erosion and associated transport driven by wind have nearly always been studied independently and in isolation of those driven by water. Therefore, holistic assessment of land surface response to climate change is precluded, and the relative roles of wind and water erosion under conditions of comingled increases in drought and intense precipitation events are unknown. We report time-series field measurements of wind and water erosion—estimated as cumulative horizontal dust flux or sediment transport, respectively—in a semiarid grassland in southern Arizona, USA for an interval spanning an intense 25-year precipitation event directly followed by the driest 9-month period (September – May) on the >100-year instrumental record. We evaluated both types of erosion under baseline conditions and under disturbed conditions associated with prescribed fire and livestock grazing. We also evaluated wind erosion at the scale of individual vegetation patches, contrasting that with associated studies for water erosion.
Results/Conclusions
The unusual conditions during this one-year interval can be viewed as analogous to those projected to accompany climate change. Notably, wind erosion exceeded water erosion by a factor of ~50, jumping up by more than an order-of-magnitude relative to baseline conditions. Grazing and especially fire amplified the rates of both types of erosion and influenced the relative ratio of wind to water erosion. Our results indicate that dust emissions will likely dominate water-driven sediment production under such global-change-type climate conditions, that fire can particularly amplify these rates, and that changes in vegetation patches are important in the context of desertification and land-surface dynamics. More generally, our results highlight the need for more careful land management to avoid further amplification of dust emissions such as those that resulted from post-1880 cattle grazing in western USA.
