Proactive Coral Reef Restoration Using Thermally Tolerant Corals in Hawaiʻi

Effective conservation of degraded ecosystems requires mitigation of the original cause of decline, but this step can be difficult in the context of global climate change. On coral reefs, persistent environmental stress which causes coral bleaching may be addressed by using coral restoration stock which is naturally more resilient, often termed "proactive restoration" in terrestrial management. To explore the feasibility and consequences of this approach, we outplanted 391 colonies of 7 species of reef-building coral designated as 'thermally tolerant' or 'thermally sensitive' during stress testing and monitored them for 2 years using photogrammetry to evaluate tradeoffs and return-on-effort. We found no growth, complexity or effort tradeoffs when using thermally tolerant corals, but tolerant corals had lower survivorship during our monitoring period, driven primarily by one genus. These data illustrate nuanced tradeoffs and consequences to proactive reef restoration and suggest that the potential benefits of this approach may only be fully realized during future coral bleaching events.