Reductions in Ghost Crab Populations Reflect Urbanization of Beaches and Dunes

Abstract

Coastal management is being challenged to develop and implement measures that safeguard the ecological values of beach and dune ecosystems, particularly in urban settings. Monitoring the efficacy of such interventions requires reliable indicators of ecological change. Here, we tested the efficacy of ghost crabs (Genus Ocypode) to reflect changes in the degree of human beach use and habitat modifications. This was done across six beaches that differed in the degree of "urbanization" on Australia's Gold Coast, which ranks amongst the country's most intensively developed coastal areas. Population densities of crabs closely match the levels of beach use and human disturbance: Beaches with fewer visitors are less likely to be raked mechanically, thereby, supporting significantly higher numbers of crabs than do beaches with more visitors, which are cleaned more frequently. These spatial differences were consistent across eight surveys. Beaches backed by wider dunes that were more densely vegetated were better habitats than were the beaches with severely modified dunes. From a management perspective, our findings emphasize the critical role of maintaining-and possibly restoring-all remnant dune habitats. A premium on conserving dunes should be complemented by continued visitor management and new initiatives to develop and use more ecologically sensitive beach cleaning techniques.