We examine the effects of landscape, population size and habitat quality on dispersal of the non-threatened, non-endangered butterfly Parnassius smintheus. Studies were done in a region where rapid rise in tree line is reducing the size, and increasing the isolation of alpine meadows in the Rocky Mountains of Western Canada. Using mark-recaputure methods and microsatellite DNA markers we determine that intervening and encroaching forests reduce the dispersal of butterflies by one-half to one-fifth. Dispersal is greater from small rather than from large populations. Experimental studies indicate that low emigration from large populations is due to the correlation between population size and meadow quality; butterflies don’t leave good meadows.