Global loss and degradation of natural areas, primarily through road construction and the ensuing disturbance by humans, constitutes a major threat to persistence of wildlife populations. I hypothesized that many of the extirpations of reptile populations in Ontario are due to expanding human disturbance and predicted that road density and land cover will explain the reduced and fragmented ranges of reptile species within Ontario. Historic road data and accounts of population extirpations revealed that road densities associated with extirpated populations were significantly higher than road densities associated with extant populations. Indicators of human activity explained up to 84.1% of the variation in reptile species distribution. The size, location and level of development of Ontario's protected areas were examined to determine their potential as "safe havens" for Ontario's reptiles. Results suggest that Ontario's protected areas may not be adequate to maintain some reptile species within southern Ontario.