Vegetation and ghost crabs in coastal dunes as indicators of putative stressors from tourism

Coastal dunes provide important ecosystem services and are susceptible to human disturbance such as vehicle traffic and human trampling. Notwithstanding, on several Australian beaches dunes serves as camping areas, where camping sites are located on the primary dunes landwards of the foredunes. Because these activities have the potential to impact on the biota of the foredunes directly adjoining the camping zones, sustainable management of dunes for multiple uses requires that putative impacts are identified. Consequently, we quantified: (1) effects of dune camping on the vegetation in the foredunes abutting the camping zones, (2) ghost crab (Ocypode cordimana) abundance, distribution, body size, and body condition as biological indicators of human stressors, and (3) the degree to which habitat attributes are correlated with ghost crab abundance. Two percent of the foredune surface was disturbed by human activity (vehicle tracks, trampling, dog prints, litter). Camping in the primary dunes had some minor effects on the vegetation of the foredunes, but widespread changes in plant assemblages were not detected. Ghost crabs were attracted to camp sites, significantly changing their distribution across the dune field and increasing their body condition near camp sites—presumably a trophic subsidy from food scraps. Except for vegetation height which had a positive influence on crab density, there were no other strong and consistent predictors of ghost crab density either in terms of physical habitat attributes (e.g. dune width and height) or vegetation characteristics (e.g. plant cover, diversity). Because coastal managers must increasingly reconcile multiple uses of the environment with its protection, robust data on the type, extent and magnitude of impacts are critical to formulate efficient management strategies for dunes. Monitoring the efficacy of such strategies requires robust indicators, and we show that ghost crabs may be good candidate species for this.