Abstract
On the iconic Great Barrier Reef (GBR), the cumulative impacts of tropical cyclones, marine heatwaves and regular outbreaks of coral-eating crown-of-thorns starfish (CoTS) have severely depleted coral cover. Climate change will further exacerbate this situation over the coming decades unless effective interventions are implemented. Evaluating the efficacy of alternative interventions in a complex system experiencing major cumulative impacts can only be achieved through a systems modelling approach. We have evaluated combinations of interventions using a coral reef meta-community model. The model consisted of a dynamic network of 3753 reefs supporting communities of corals and CoTS connected through ocean larval dispersal, and exposed to changing regimes of tropical cyclones, flood plumes, marine heatwaves and ocean acidification. Interventions included reducing flood plume impacts, expanding control of CoTS populations, stabilizing coral rubble, managing solar radiation and introducing heat-tolerant coral strains. Without intervention, all climate scenarios resulted in precipitous declines in GBR coral cover over the next 50 years. The most effective strategies in delaying decline were combinations that protected coral from both predation (CoTS control) and thermal stress (solar radiation management) deployed at large scale. Successful implementation could expand opportunities for climate action, natural adaptation and socioeconomic adjustment by at least one to two decades.
Highlights
The Great Barrier Reef (GBR) is the largest living structure on the planet and currently under intense pressure from climate change and other threats
GBR interventions likely to be technically feasible and cost-effective within the near future have previously been identified. We have tested these strategies within a reef meta-community model describing key physical and biological processes operating on coral reef systems exposed to tropical cyclones, impacts from flood plumes, mass bleaching events and ocean acidification
The Coral Community Network (CoCoNet) model has been calibrated against the Australian Institute of Marine Science (AIMS) Long-Term Monitoring Program (LTMP) dataset [55] at both the individual reef scale [28,56] and reef network scale [17]
Summary
The Great Barrier Reef (GBR) is the largest living structure on the planet and currently under intense pressure from climate change and other threats. A crown-of-thorns starfish (CoTS) outbreak began on the GBR in 2010 [1] exacerbating coral mortality associated with a decade of severe tropical cyclones (notably Hamish in 2009, Yasi in 2011 and Debbie in 2017) and successive mass coral bleaching events in 2016, 2017 and 2020 [2,3]. Their cumulative impacts have depleted coral cover to some of the lowest levels in recorded history. We consider a diverse range of interventions, including some that are yet to be tested in situ or at large scale
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