Rebuilding coral reefs: does active reef restoration lead to sustainable reefs?

The coral reefs worldwide are exposed to multiple anthropogenic threats and persisting global change impacts, causing continuous degradation, also calling for the development of novel restoration methodologies. Of the most promising emerging approaches, deriving its rationale from silviculture, is the low-cost 'gardening concept', guided by a two-step restoration operation: (a) mid-water nursery phase, where coral-nubbins are farmed and (b) transplantation of nursery-farmed colonies. Tested worldwide, at least 86 coral-species and over 100 000 colonies were successfully farmed in different archetype nurseries, and several novel transplantation methodologies were developed. A number of unanticipated emerged outcomes were the immediate establishment of coral infaunal biodiversity in nurseries, the development of nurseries into 'larval dispersion hubs' and the enhanced reproduction of transplanted coral colonies. Altogether, and in addition to envisaged results (e.g., high survivorship, fast coral growth), results attest that the gardening-toolbox could serve as a ubiquitous ecological engineering platform for restoration on a global scale.