Coral reef ecology and conservation in the tropical Pacific Ocean

Both local and global stressors threaten coral reefs, putting the food security, cultural continuity, and livelihoods of millions of reef-dependent people at risk. Still, scientists lack an understanding of how climate-driven heat stress interacts with local stressors such as fishing and pollution to influence reef health. Coral reef communities in the Marshall Islands and Kiribati, both low-lying atoll nations in the central Pacific, offer an opportunity to examine these interactions. The Gilbert Islands of Kiribati, which straddle the equator, experience highly variable sea surface temperatures (SSTs) inter-annually due to El Niño / Southern Oscillation, driving coral bleaching events in 2004/2005 and 2009/2010, while the Marshall Islands further north of the equator experience more stable SSTs. Both nations are home to degraded reefs near their capitol atolls, which host over half of each country’s populations. I first analyzed the benthic trajectories of coral reefs in the Gilbert Islands from 2012, 2014, 2016, and 2018, across a gradient of local human disturbance after multiple stressors, including two heat stress events and an outbreak of the corallivorous Crown-of-Thorns (CoTs) starfish, finding that locally degraded reefs were more resistant to heat stress than less trafficked reefs because the former were home to hardier taxa. Next, comparing locally disturbed and undisturbed reefs in Kiribati to those in the Marshalls demonstrated that the interactions between local and global stressors were context-dependent; the taxa that were present dictated the interactions. Then, via a meta-analysis of 1,205 sites in the Indian and Pacific Oceans, I demonstrated that a proxy often used to assess the effects of local human disturbance on reef health, the percent cover of macroalgae, does not correlate with local human disturbance. Instead, different genera of macroalgae exhibited diverse and often opposing responses to various sources of local human disturbance. Finally, I used public archives from an email listserv popular among the coral conservation community to analyze the policy narratives used by participants when discussing local threats to reefs, the actors involved in the local threat, their distal drivers, and the proposed solutions, revealing underlying assumptions about reefs and local people, which could inadvertently undermine conservation.