Investigating historical, social, and ecological dimensions of coral reef resilience

Abstract

Coral reefs are complex social-ecological systems that shape, and have been shaped by, a range of historical, environmental, and social processes. Global declines in reef health highlight the need to understand the factors that support reef resilience and those that further decline. This dissertation uses multiple methodologies and approaches to explore different aspects of resilience, integrating marine historical ecology, biocultural approachces, and large-area imaging to assess benthic habitats. I investigate the historical ecology of the 1000-year-old pole-and-line tuna fishery in the Maldives archipelago and examine the reasons for its persistence over time. Written accounts of traders and travelers, ethnographies, and archaeological data indicate that a centuries-long trade in money cowries served as a condition for the establishment of the tuna fishery, which in turn drove cultural and market dynamics towards the consumption of pelagic fish. This preference for tuna has kept reef fishing historically light, but new markets for reef fish are changing local consumption patterns. I conducted interviews with residents and fishers across one of the central atolls in the Maldives to better understand the ways in which different species of fish are valued today. Results indicate that reef fish have been an overlooked part of local diets, with preferences that vary strongly with gender and age. Seasonal spikes in the local catch and consumption of reef fishes and an informal network of sharing point to previously undocumented local practices that should be considered while developing management plans. Finally, these social and cultural shifts are taking place as coral reefs alter in function in response to increasingly frequent climate change related marine heatwaves. During one such thermal stress event in Kāneʻohe Bay, Oʻahu in 2019, I used structure-from-motion photogrammetry to quantify the fine-scale spatial, temporal, and taxonomic differences in coral bleaching and mortality. Spatial differences in bleaching were strongly linked to habitat complexity and coral composition, with reefs that were dominated by Pocillopora experiencing most severe bleaching. Mortality was also influenced by species composition and fine-scale differences in thermal stress, with heat-susceptible species seeing significant declines in cover in this period. Together my results highlight the importance of integrating human dimensions into our understanding of reef resilience, and the role that emerging technologies can play in quantifying the environmental and ecological processes that underpin reef response to climate change.