Recent stabilization of active sand dunes on the Canadian prairies and relation to recent climate variations

The historical activity of sand dunes on the southern Canadian prairies was investigated in order to determine the relation with recent climate variations. Changes in dune activity were determined from historical aerial photographs at seven sites with active parabolic dunes in Saskatchewan and Manitoba. The methodology developed combines digital image processing and geographical information system (GIs) analysis to measure changes in dune activity from the aerial photographs, as well as correlation analysis to determine the relation between dune activity and climate variations. Overall, dune activity has been decreasing since the early to mid 1900s as evidenced by greater vegetation colonization than sand dune migration or reactivation. The decrease in dune activity is significantly correlated with decadal-scale variations in aridity and is coincident with a decrease in annual wind speed. Evidence suggests that this response is superimposed on a longer trend towards stabilization, possibly in place since the late 1700s. Taken together, the effect of this complex response is that dune recovery on the southern Canadian prairies is prolonged well after an initial disturbance and therefore gives the impression of anomalous levels of activity for extended periods thereafter. For this reason, dune mobility indices predicated on short-term climate variations (years to decades) do not fully describe the present level of dune activity on the southern Canadian prairies. (c) 2004 Elsevier B.V. All rights reserved.