Abstract Summary
Restoration or assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed, may become critical in areas without enough intact coral reef habitat left to protect due to climate change, coastal development, pollution, and overfishing. However, restoration decisions are often impeded by the lack of information about cost and feasibility and the specific reasons why to restore. Here, we synthesise data from the restoration literature to evaluate restoration cost, survival of restored organisms, project duration, area, and techniques which have been employed on coral reefs around the world. Findings showed that restoration cost had an overall global median of 471,621 US$ ha-1 (2010 US$). Grouped by techniques, the median cost ranged between 5,616 US$ ha-1 for the nursery phase of the coral gardening approach and 3,911,240 US$ ha-1 for substrate addition to build an artificial reef. Restoration projects were mostly short-lived (1-2 years), carried out over small experimental scales (0.01 ha), and reported 60.9% as the median survival of restored corals. The main motivations to restore coral reefs were to further our knowledge and improve the methodological approach while growth and survival were the main variables monitored. Most studies reported an ecological outcome, seldom joined with social or socio- economic results. The findings and database may support practitioners tasked to make decisions on whether, what, how, where, how much, and why to restore. The current challenge for coral reef restoration is to scale-up restoration efforts to reasonable ecological, social and economic scales and over longer time periods.
