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The possible impact of increased aridity on sand dune activity on the Canadian Prairies is evaluated by comparing dune mobility indices for the period 1961-1990 to those for the 1988 drought year. The 30-year mean mobility indices, with P:PE ratios ranging from 0.50 to 0.90, indicate dunes to be presently either inactive or having only crests active. Using a scenario in which drought conditions of 1988 were prolonged, dune activity in the region is predicted to increase with the most arid localities having active dunes accompanied by vegetated interdune areas. The central region of the prairies would have a semi-arid rather than sub-humid climate, with P:PE ratios as low as 0.30. Despite the increase in aridity, sand dunes in the region would most likely remain parabolic. (C) 1997 Academic Press Limited.