Abstract
The accelerating marks of climate change on coral-reef ecosystems, combined with the recognition that traditional management measures are not efficient enough to cope with climate change tempo and human footprints, have raised a need for new approaches to reef restoration. The most widely used approach is the “coral gardening” tenet; an active reef restoration tactic based on principles, concepts, and theories used in silviculture. During the relatively short period since its inception, the gardening approach has been tested globally in a wide range of reef sites, and on about 100 coral species, utilizing hundreds of thousands of nursery-raised coral colonies. While still lacking credibility for simulating restoration scenarios under forecasted climate change impacts, and with a limited adaptation toolkit used in the gardening approach, it is still deficient. Therefore, novel restoration avenues have recently been suggested and devised, and some have already been tested, primarily in the laboratory. Here, I describe seven classes of such novel avenues and tools, which include the improved gardening methodologies, ecological engineering approaches, assisted migration/colonization, assisted genetics/evolution, assisted microbiome, coral epigenetics, and coral chimerism. These are further classified into three operation levels, each dependent on the success of the former level. Altogether, the seven approaches and the three operation levels represent a unified active reef restoration toolbox, under the umbrella of the gardening tenet, focusing on the enhancement of coral resilience and adaptation in a changing world.
Highlights
Decades of continuous and substantial global climate change impacts, together with accumulated anthropogenic footprints on coral reefs, have demonstrated that, excluding a few remote reef sites, all major reefs suffer from accrued degradation, and a complete reshuffling of their biological diversity as they transform into less diverse ecosystems [1,2,3]
Coral reef communities will most likely be in a state of flux for years to come, driven by different climate change drivers [8] with multiple stressors that act in tandem [9] and increase the risk of phase shifts into algal dominated reefs
This has prompted a surge in active restoration initiatives that can be divided into seven major research avenues added to the gardening approach (Table 1); each avenue is formulated in such a way as to guide an effective reef restoration tactic
Summary
Decades of continuous and substantial global climate change impacts, together with accumulated anthropogenic footprints on coral reefs, have demonstrated that, excluding a few remote reef sites, all major reefs suffer from accrued degradation, and a complete reshuffling of their biological diversity as they transform into less diverse ecosystems [1,2,3]. Use of herbivorous fish/invertebrates for improved nursery maintenance; animal-assisted cleaning; engineering of larval supply through transplantation of nursery-farmed gravid colonies; transplantation of ecological engineering species; development of larval hubs and ‘artificial spawning hotspots’; tiling the reef; nubbin fusions for enlarged colonies; micro-fragmentation; serially positioning nurseries to create new mid-water coral biological corridors through stepping stone mechanisms; using dietary habits of grazers as biological controls of fouling macroalgae; large scale restoration acts; enhanced calcification/survival rates via seawater electrolysis Moving species outside their historic ranges may mitigate loss of biodiversity in the face of global climate change. I’ll summarize some of the major aspects and the hierarchy of these reef restoration avenues and approaches, which form the first toolbox to be used for enhancing coral resilience and coral adaptation in a changing world
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