Depletion of ghost crabs on urban beaches over 25 years

Adverse impacts of human-induced modifications to the seascape, particularly urbanisation, are widely reported in sandy-beach ecosystems. However, few, if any, studies have adequate temporal replication over decades, making inferences about the duration of impacts somewhat tenuous. Here we resurveyed beaches originally sampled 25 years ago to assess whether ghost crab burrow density, an indicator of ghost crab abundance, continues to reflect patterns of urbanisation and human impact. Burrow abundance remained consistently lower on urban beaches than on non-urban beaches, confirming the robustness of this indicator despite natural variability. Populations on armoured and intensively trampled urban beaches remain depleted, with no evidence of recovery over the study period, suggesting that natural recolonisation is unlikely without management interventions. On non-urban beaches, we detected a decline in burrow density at dune toes, possibly linked to the use of off-road vehicles. Burrow abundance was positively associated with dune vegetation, highlighting the importance of preserved dune systems. These findings indicate both the persistence of long-term human impacts and the emergence of negative effects on non-urban beaches. We recommend management experiments to limit trampling and traffic and establish exclusion zones in upper urban beach areas. Overall, ghost crab burrow density remains a reliable, practical indicator of impact, and its continued application can be used to cost-effectively support conservation of sandy beach biodiversity and ecosystem functioning.