Context‐dependent benefits of coral reef restoration

Abstract Introduction Climate change creates dire prospects for coral reefs over the coming decades, prompting interest in whether restoration strategies could mitigate some of the projected decline. Restoration benefits are context dependent, being influenced by reef state (ecological, connectivity and demographic conditions, etc.), intervention design (e.g. size of restored area and number of corals), and the impact of disturbance occurring post‐coral deployment. Objectives Here, we use an individual‐based ecological model to quantify the importance of context in driving restoration benefit. Methods Specifically, we focus on the intervention of out‐planting corals on a single reef, parameterized to conditions found on the Great Barrier Reef. Results Our results show that out‐plant density and size of the restoration area contribute to restoration success, particularly when disturbance pressure on the reef is limited. Specifically for the ecological context, we find that larval supply is an important driver of restoration success, with benefits predominantly increasing when larval supply is low and self‐retention is high. Thereby, restoring reefs where larval supply is low showed a four‐fold increase in benefits compared to doubling the restoration effort. Species composition is important with greater benefits predicted when the restored reef is not comprised of Acroporidae pre‐restoration. Benefits are also sensitive to the timing of disturbances, with post‐disturbance benefits increasing nonlinearly at reefs with low larval supply and retention until 10–12 years post‐restoration after which benefits are retained. Conclusions Our results highlight the importance of context when designing and evaluating reef restoration as well as setting credible expectations of success.