Effects of diamond mining on sandy beaches in southern Namibia – the use of Tylos granulatus (Isopoda: Oniscidea) as an indicator species

Abstract

Sandy beaches provide vital ecosystem services and support diverse ecological communities but are increasingly threatened by anthropogenic pressures. In particular, intertidal mining disrupts sandy beaches and challenges their resilience, yet these ecosystems retain some capacity for environmental recovery. This study assessed the ecological impact of, and potential recovery from, diamond mining on southern Namibia’s sandy beaches within the Restricted Diamond Mining Area, using the isopod Tylos granulatus as a bioindicator. Paired control and impact sites were surveyed before, during and after mining to estimate T. granulatus abundance and population size structure. Mining onset and activity led to significant declines in T. granulatus abundance at all impact sites, including local extirpation in some cases. While overall abundance showed significant recovery within 1–2 years following mining cessation, the population size structure remained substantially altered for at least 4 years on actively rehabilitated beaches, and for at least 7 years where recovery was left to occur naturally. These findings demonstrate the environmental effects of mining on beach ecosystems while demonstrating the recovery potential (albeit gradual) of these habitats. Our results support T. granulatus as a cost-effective indicator of environmental stress on sandy beaches, while offering critical insights for sustainable management of vulnerable shorelines in southern Africa.