Despite rampant coastal development throughout Southeast Asia and the Pacific, studies of conservation genetics and ecology of vulnerable, coastal species are rare. Large bodied vertebrates with highly specialized habitat requirements may be at particular risk of extinction due to habitat degradation and fragmentation, especially if these habitats are naturally patchily distributed, marginal, otherwise geographically limited, or associated in space with high human population densities or heavy anthropogenic disturbance. Particularly telling examples of these conservation challenges are large Australasian reptiles with obligate habitat requirements for lowland, coastal and mangrove forests. Plagued by habitat destruction due to high human densities along coastlines, sprawling rural development, and rapidly developing estuarine fisheries industry, coastal forest reptiles are experiencing rapid declines. And yet studies of population biology, genetics, and habitat requirements of species depending on these environments are few. We undertook the present study in order to take a multifaceted approach to understanding a poignant conservation problem. We identify significant evolutionary units for conservation in large-bodied sailfin lizards (genus Hydrosaurus), model suitable habitat in the Philippines from extensive occurrence data and evaluate the efficacy of the current protected area network, and identify the source of hydrosaurs in the illegal pet trade. We determine that the extent of the species’ habitat coincident with protected areas is low. Our forensic evaluation of the illegal pet trade in the Philippines determines the existence of a natural population that is at risk of systematic exploitation by traders. Together, this integrative study characterizes a conservation urgency of particular significance: the genetically distinct sailfin lizards of the Bicol faunal region, with suitable habitat virtually unprotected, and clear evidence of heavy exploitation for illegal trade. To the best of our knowledge, our study is the first conservation genetic study to evaluate the potential effectiveness of the protected landscape coverage in the Philippines, a Megadiverse nation and Biodiversity Hotspot.