Charting two centuries of transformation in a coastal social-ecological system: A mixed methods approach

Oyster reef ecosystems used to form significant components of many temperate and subtropical inshore coastal systems but have suffered declines globally, with a concurrent loss of services. The early timing of many of these changes makes it difficult to determine restoration targets which consider interdecadal timeframes, community values and shifted baselines. On the Australian continent, however, the transition from Indigenous (Aboriginal) to Westernized resource use and management occurred relatively recently, allowing us to map social-ecological changes in detail. In this study, we reconstruct the transformations in the Sydney rock oyster (Saccostrea glomerata) wild commercial industry of central and southeast Queensland, and by extension its reef ecosystems, as well as the changing societal and cultural values related to the presence and use of the rock oyster through time. By integrating data from the archaeological, anthropological and fisheries literature, government and media accounts, we explore these transformations over the last two centuries. Before the 1870s, there was a relative equilibrium. Aboriginal peoples featured as sole traders to Europeans, supplying oysters and becoming a substantial component of the industry's labour pool. Effectively, Australia's commercial oyster industry arose from Aboriginal-European trade. During this initial phase, there was still a relative abundance of wild oyster, with subtidal oyster reef structures present in regions where oysters are today absent or scarce. By contrast, these reefs declined by the late 19th century, despite production of oysters increasing due to continued large-scale oyster recruitment and the expansion of oyster cultivation in intertidal areas. Production peaked in 1891, with successive peaks observed in regions further north. During the 1890s, flood events coupled with land-use changes introduced large quantities of silt into the system, which likely facilitated an increase in oyster pests and diseases, ultimately decreasing the carrying capacity of the system. Today oyster production in this region is less than one-tenth of historical peak production. Many cultural heritage components have also been lost. Indigenous management is now very minor due to the massive decimation of Aboriginal populations and their respective practices. Yet, we found strong cultural attachment to midden remains and oyster production continues within Indigenous communities, with considerable broader community support. This study highlights the value of conducting thorough analysis of early media accounts as a means for reconstructing historical resource decline and management. It further demonstrates the application of historical information and context for contemporary management, protection and restoration of much-altered coastal social-ecological systems.