Human exploitation of shellfish in the Atacama desert coast and environmental variability: a trans-Holocene perspective

The Humboldt upwelling ecosystem has been intensively harvested by people since the early Holocene. Understanding past and present human choices under climatic variability in these productive environments may hold key insights for its future sustainability by unraveling different adaptive pathways. To this end, we studied shellfish exploitation and climate patterns in the Taltal region of the Atacama desert coast (25{whitebullet}S) from the early Holocene until today using a compilation of archaeological, and modern benthic fisheries data together with direct ecological surveys. In addition we obtained satellite sea surface temperature (SST) and published{delta} 18O SST for the study region. The archaeological record and the modern rocky shore assemblage were dominated by herbivorous gastropods -Fissurella spp., Enoplochiton spp., Tegula spp.-and the carnivorous whelk Concholepas concholepas. Functional composition from the early Holocene to the present was remarkably stable. Using SST as a latent variable, we examined changes in functional composition across the Holocene and in a 16-year series of artisanal fisheries landings using bayesian ordination. The analysis identified functional groups characteristic of kelp ecosystems in association with cooler SST conditions during the Holocene and the present. Changes in functional composition during warm and cold periods of the Holocene broadly mirrored effects of interannual SST variability in the modern fisheries. The archaeological record suggests two cross-Holocene transitions social-ecological transitions. The generalized shoreline harvesting strategy that prevailed during the cold early Holocene shifted to a specialized maritime economy towards the warmer mid-Holocene. The maritime technological and cultural adaptions remained, but were part of more diversified lifestyles in the cooler and more variable late Holocene. The latter emerged at the same time as the modern El Nino climate pattern. Our insights from the direct analysis of human choices and SST variability highlight the role of flexibility and agency under a changing environment. The broad range of human decisions in the past, inform current regulatory frameworks for benthic artisanal fisheries. Marine resources and the livelihoods that depend on them are integrated into coupled coastal socioecological systems; their future sustainability hinges on fostering the different dimension of their adaptive capacity.