VANISHING IBERIAN CLAMS: LOCAL CONSEQUENCES AND GLOBAL IMPLICATIONS OF ACCELERATING LOSS OF SHELLS TO TOURISM

Shells of dead invertebrates perform various natural functions in coastal environments with diverse ecological, geomorphological and geochemical implications. Shell removal by tourists, including collecting and inadvertent destruction, may play an important role in reducing the quantity of bioskeletal remains in coastal settings, but rigorous data assessing measurable impacts of those activities are scarce. Here we estimate multi-decadal increase in shell removal by tourists via two series of monthly surveys conducted thirty years apart (1978-1981 and 2008-2010). Those surveys were carried out along the shoreline of Llarga Beach, a small embayment on the Mediterranean coast of Spain. The study area has remained unaffected by direct urban encroachment and commercial fisheries.

Over the last 30 years, the local tourist arrivals in the study area have increased almost three-fold (2.74). Concomitantly, as quantified by the shoreline surveys, abundance of mollusk shells decreased by a comparable factor (2.62) and displayed an inverse correlation with tourist arrivals across seasons. In contrast, ecological parameters measurable from beach shell assemblages have remained static during the same time interval. A four-fold increase in global tourist arrivals observed over the last 30 years has likely induced a comparable acceleration in anthropogenic removal of shells from worldwide shorelines and may have exerted multiple (currently unquantifiable) changes including increased beach erosion, changes in calcium carbonate recycling, and decline in diversity and abundance of shell-dependent organisms.

Shell sequestration by tourists and other anthropogenic processes that affect dead shellfish remains represent a promising research direction in Conservation Paleobiology.