Persistence of ghost crabs in a highly urbanised estuary

The accelerating destruction of natural habitats by rapidly expanding human populations has caused impacts to ecosystems around the globe. Sandy beaches are no exception to this, with intense coastal development and increasing... [ view full abstract ]

The accelerating destruction of natural habitats by rapidly expanding human populations has caused impacts to ecosystems around the globe. Sandy beaches are no exception to this, with intense coastal development and increasing recreational use resulting in widespread modifications of these ecosystems. Beaches in urban areas are now trapped in a ‘coastal squeeze’ between the impacts from urbanisation on the terrestrial side and the manifestations of climate change on the ocean side. Ghost crabs from the genus Ocypode are important consumers on sandy beaches and have been found to be susceptible to human activities such as trampling and beach grooming. We surveyed 37 sandy beaches in a highly urbanised estuary, Port Jackson (Sydney Harbour), to test the relative importance of biotic and abiotic variables, including human activities and management practices on the abundance of the ghost crab Ocypode cordimana. Abundances were highly variable among beaches within the harbour, but were not effectively predicted by abiotic variables of beach length, slope, and grain size and organic content of sediments. There were some effects of beach cleaning regimes, but no variation among beaches with differing degrees of habitat modification (seawalls and presence of coastal vegetation). Our results suggest ghost crab populations in Sydney Harbour are more robust to the impacts of urbanisation than originally thought and gives hope to the persistence of similar populations in increasingly urbanised environments.