Insights into coral restoration projects in Japan

Coral transplantation, including out-plantation, is performed worldwide to restore coral reefs. To date, >300 000 coral colonies have been transplanted in Japan, and the survival rate of transplanted corals is mostly <20% after 4 years. Here, we highlight problems that have arisen as a result of coral restoration projects in Japan and discuss solutions that may maximise transplantation effectiveness. The government, companies, and researchers have focused on the positive aspects of transplantation technology and new biological findings; however, negative aspects such as the high mortality rate for transplanted corals and high maintenance costs have garnered less attention. Uncritical and incomplete coverage of reef projects by the mass media has led to a misconception that the coral reef crisis can be resolved by current biological engineering solutions. Therefore, transplantation has been used to justify sea reclamation including marine leisure facilities and various other construction projects. Consequently, approximately 400 ha of coral reefs in Japan have been lost in only a decade. Understanding the limitations of transplantation techniques is necessary, and hence, we propose that coral transplantation guidelines be adopted to prevent further loss. Further advances in transplantation technology are required to increase scalability and cost-effectiveness and improve survival/performance; however, practitioners, researchers, companies, and governments, especially in environmentally unconscious countries, should clearly state that coral transplantation cannot restore large-scale coral reef ecosystems and should not be used to justify land reclamation affecting reefs, as mentioned in most international guidelines. Moreover, when coral transplantation and seedling production are used for environmental education, the death of transplanted corals and difficulties underlying artificial coral regeneration should be clearly explained. Effective coral transplantation use within a conservation framework is critical to avoid high and unfounded expectations.