Global climates are rapidly changing, which for many species will require dispersal to higher altitudes and latitudes to maintain favourable conditions. Changes in distribution for less mobile species is likely to be associated with losses to genetic diversity, yet this cannot be quantified without understanding which parts of a species distribution will colonise favourable regions in the future. To address this we adopted a realistic estimate of dispersal with predicted changes in species distributions to estimate future levels of intraspecific genetic diversity. Using 740 geckos (Gehyra variegata) collected across their distribution in central and eastern inland Australia, we predict genetic loss within phylogenetically distinct units at both mtDNA and microsatellite markers between 2010 and 2070. We found that using a quantified and realistic estimate of dispersal resulted in significant declines to allelic richness (5.114 to 4.052), haplotype richness (7.215 to 4.589) and phylogenetic diversity (0.012 to 0.005) (P<0.01). In comparison, predicted losses were substantially over- or underestimated when commonly applied dispersal scenarios were utilised. Using biologically relevant estimates of dispersal will help estimate losses of intraspecific genetic diversity following climate change impacts. This approach will provide critical information for the management of species in the near future.