Shifting paradigms in restoration of the world's coral reefs

Abstract

Many ecosystems around the world are rapidly deteriorating due to both local and global pressures, and perhaps none so precipitously as coral reefs. Management of coral reefs through maintenance (e.g., marine-protected areas, catchment management to improve water quality), restoration, as well as global and national governmental agreements to reduce greenhouse gas emissions (e.g., the 2015 Paris Agreement) is critical for the persistence of coral reefs. Despite these initiatives, the health and abundance of corals reefs are rapidly declining and other solutions will soon be required. We have recently discussed options for using assisted evolution (i.e., selective breeding, assisted gene flow, conditioning or epigenetic programming, and the manipulation of the coral microbiome) as a means to enhance environmental stress tolerance of corals and the success of coral reef restoration efforts. The 2014-2016 global coral bleaching event has sharpened the focus on such interventionist approaches. We highlight the necessity for consideration of alternative (e.g., hybrid) ecosystem states, discuss traits of resilient corals and coral reef ecosystems, and propose a decision tree for incorporating assisted evolution into restoration initiatives to enhance climate resilience of coral reefs.

The Future of Coral Reefs Subject to Rapid Climate Change: Lessons from Natural Extreme Environments

“…Reduction of emissions, in particular carbon dioxide, is undoubtedly required to preserve the future form, function and ecosystem services of coral reefs (Gattuso et al, 2015;Hughes et al, 2017). But there is also an increasing debate over the need to facilitate coral survival through proactive reef management, e.g., reef restoration and/or assisted evolution processes (e.g., Coles and Riegl, 2013;van Oppen et al, 2015;Oppen et al, 2017). The use of proactive reef management is highly debated and beyond this synthesis (see van Oppen et al, 2015;Oppen et al, 2017), but what is evident from these extreme environments is the presence of corals that have traits highly favorable for future survival.…”

“…But there is also an increasing debate over the need to facilitate coral survival through proactive reef management, e.g., reef restoration and/or assisted evolution processes (e.g., Coles and Riegl, 2013;van Oppen et al, 2015;Oppen et al, 2017). The use of proactive reef management is highly debated and beyond this synthesis (see van Oppen et al, 2015;Oppen et al, 2017), but what is evident from these extreme environments is the presence of corals that have traits highly favorable for future survival. For many environments we still do not know how these traits may be conserved or lost as corals are moved to new environments, however evidence of heritable heat-tolerance and conserved thermal tolerance (Hume et al, 2013) has been reported.…”

Adaptation to reef habitats through selection on the coral animal and its associated microbiome

“…The potential of such populations to serve as a source for adaptive genetic variation for surrounding habitats remains poorly explored. Potentially, these populations can provide adaptive alleles that could be harnessed in assisted gene flow or selective breeding initiatives that aim to increase climate resilience in the receiving populations (Hoegh‐Guldberg et al., ; van Oppen, Oliver, Putnam, & Gates, ; van Oppen et al., ).…”

Interspecific Hybridization May Provide Novel Opportunities for Coral Reef Restoration

“…Several observations of an increase in tolerance of coral bleaching after successive bleaching events suggest that adaptation and/or acclimatization are possible under certain conditions (Maynard et al, 2008;Berkelmans, 2009;Guest et al, 2012;Penin et al, 2013). Nevertheless, over 50% of the world's coral reefs has been lost in the last three decades, with the Caribbean having lost over 80% of its coral cover (50 Reefs, 2017) 1 , indicating that the rates of natural adaptation and acclimatization are overall insufficient to keep pace with the rate of environmental changes (van Oppen et al, 2017).…”

“…An effective restoration strategy should thus incorporate an understanding of present day ecological characteristics of species, characteristics of future available habitats, and adaptive potential of species (Becker et al, 2013). The use of non-local and climate resilient materials is controversial, but is gaining traction in wildland restoration (Jones and Monaco, 2009), revegetation Breed et al, 2013), and coral reef restoration (Rau et al, 2012;van Oppen et al, 2017).…”