Coral Restoration: Comparisons in Space, Time, Impacts, and Costs
Abstract
Seventy-five percent of coral reefs globally face crisis due to anthropogenic disturbances, prompting heightened global coral restoration initiatives to preserve these vital ecosystems. Various regions employ diverse active coral restoration methodologies, including coral gardening, transplantation, micro-fragmentation, artificial reefs, and sexual propagation. Of these methods, coral gardening stands out as one of the most common and highly successful methods, alongside widespread transplantation practices. Restoration efforts predominantly focus on acroporids due to their relatively rapid growth and asexual fragmentation; however, a diverse range of coral species, including large, slow-growing varieties, is also employed in these endeavors. Costs vary significantly, ranging from $10,000 to $50,000,000 USD per hectare, contingent on restoration methods and locations. Coral restoration does not address the whole problem though, achieving optimal coral survivorship post-restoration involves integrating ecological processes, coral density, and arrangement. In a Bonaire study, I utilized established coral reef monitoring sites, creating 100 m2 quadrats to assess A. cervicornis and A. palmata population density and vigor. Among 11 long-term monitoring sites, three were active restoration sites (1,796 acroporid coral outplants), three were adjacent control reefs, and five were regional control reefs. No acroporids were found at 10 m depth, but at 5 m depth, 13 acroporids were recorded at four survey sites, with five from outplant sites. The two sites with the highest acroporid densities were Calabas (restoration site) and Karpata (control site). The efficacy of coral restoration remains inconclusive based on this study of Bonaire's long-term monitored reefs.