Data and Tools to Operationalize Ridge-to-Reef Management and Build Island Resilience in Oceanic Island Environments.

Abstract

Around the Pacific, a cultural renaissance rooted in the concern over declining natural resources seeks to revive traditional ridge-to-reef management approaches to promote social and ecological resilience in a changing climate. However, the effectiveness of ridge-to-reef management remains unclear due to a poor understanding of the cumulative effects of human and natural disturbances. In high Pacific islands, land and sea are tightly connected through social and ecological processes as a result of their small size and steep elevation gradients. Therefore, new tools are needed to inform resilience management over spatial scales relevant to Pacific Islanders. This research focused on three ridge-to-reef systems under community-based-management in Hawai‘i (Hā‘ena and Ka‘ūpūlehu) and Fiji (Kubulau), which capture a wide spectrum of natural disturbances governing high Pacific islands. Based on local data from Hā‘ena and Ka‘ūpūlehu, I developed a novel predictive modeling framework linking land and sea drivers to coral reef benthic and fish indicators, at fine spatial resolution. This framework was used to determine the effects of terrestrial and marine disturbances on coral reef communities and compare the effects of coastal development coupled with climate change on coral reef benthic communities and their targeted reef fish populations, given different natural disturbance regimes. I then transferred the framework to Kubulau to assess the effects of forest cover change on downstream coral reefs given uncertain climate impacts. The results revealed that sheltered and dry oceanic environments, such as Ka‘ūpūlehu, may be particularly susceptible to reduced water quality impacts. In contrast, exposed areas, like Hā‘ena, are less susceptible to anthropogenic activities due to dilution and mixing from higher wave power and freshwater discharge. However, reef fish populations across most study sites became vulnerable to the impact of land-based source pollution when models incorporated climate change. In all cases, terrestrial management actions aimed at improving coastal water quality through wastewater management or forest conservation, coupled with the protection of coral reef nurseries or deep-water refuges, improved coral reef resilience potential. This research demonstrates that locally developed and data-driven models offer a much-needed opportunity for aiding place based management of coral reef social-ecological systems in high oceanic island environments.