Successes of soil conservation in the Canadian Prairies highlighted by a historical decline in blowing dust

Blowing dust from agricultural fields has serious health and economic effects, which can be mitigated by soil conservation techniques. However, it is difficult to isolate improved land management in downstream records of airborne dust. In this letter we present multi-decadal (1961-2006) records of airborne dust frequency from seven weather stations across the Canadian Prairies. We related temporal changes in dust frequency to the climatic wind erosion potential and agricultural census data. We identified a statistically significant regime shift in the region-wide dust time series at 1990, with a substantial reduction in dust frequency thereafter. The correspondence between dust frequency and the climatic wind erosion potential improved from 1961-90 (r(2) = 0.154, p < 0.001) to 1991-2006 (r(2) = 0.429, p < 0.001). We interpret this as indicating that the climate signal was obscured by poor soil conservation practices in 1961-90, leading to dustier conditions. Post 1990, improved land management reduced the impact of land-use practices; only the most severe climate forcings resulted in detectable dust. The dramatic reduction of dust from 1990 onward appears to represent a region-wide threshold crossing, where the effects of soil conservation efforts began to materialize. Overall, the results suggest that soil conservation initiatives have had an impact in reducing airborne dust on the Canadian Prairies.