A Decision Framework for Interventions to Increase the Persistence and Resilience of Coral Reefs (2019) / Chapter Skim
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Coral interventions that address the impacts of ocean warming and ocean acidification are part of a three-pronged approach for coral reef management that crucially also includes the mitigation of greenhouse gas emissions and the alleviation of local stressors. New coral interventions include activities that affect the genetics, reproduction, physiology, ecology, or local environment of corals or coral populations with the goal of enhancing their persistence and resilience in degraded environmental conditions.
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identify research needs that would refine the intervention strategies and reduce critical uncertainties in the environmental risk assessments; and (4) assess the potential for interventions to meet management objectives for Atlantic/Caribbean coral reefs (the full Statement of Task can be found in Box 1.1)
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For example, testing corals for heat resistance and growing them in nurseries is available to support managed selection, managed breeding, and managed relocation. In contrast, using genetic engineering to increase resilience or marine cloud brightening to reduce light and cool reef surface waters are not yet feasible, and the risks and benefits of these options are not well defined.
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The steps of this adaptive process, focused on evaluating coral interventions, are outlined below. Step 1: Identify the Decision Context An iterative adaptive management process begins with a planning and problem formulation stage to establish the decision context: identifying long- and short-term goals, objectives, possible biophysical outcomes, and their relationship to evaluation metrics and decision criteria.
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These combinations, along with uncertainty in knowledge about the reef system and future environment, will yield a range of modeled outcomes across alternatives with tradeoffs in their abilities to meet management objectives and minimize risk. For example, some intervention strategies may support the growth of a small subset of coral species that provides fish habitat but not the solid reef structure that is needed to provide coastal protection from storm waves.
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For example, a decision criterion might be to increase coral cover and diversity to create fish habitat. The associated evaluation metrics might then be abundance and diversity of coral and fish species measured at appropriate time intervals.
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AN ILLUSTRATIVE DECISION MODEL The committee provides a simple model and Bayesian network analysis to illustrate the principles of a decision analysis for a simplified reef system and the potential questions faced and insights gained from the approach. Though the results of the analysis are not reef specific, the illustration provides a concrete example of the construction of a decision support framework to analyze the risks and benefits of example interventions, evaluate the likelihood of achieving intervention goals under different scenarios, and communicate potential outcomes.
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(b) Discretetime dynamics, with survival from bleaching dependent on the amount of thermal stress (measured as degree heating weeks)
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For the example interventions, assisted gene flow occurs as an accelerated adaptation in thermal tolerance with the risks of increased mortality and decreased growth (due to outbreeding depression, demographic tradeoffs with thermal tolerance, and disease introduction) , and shading occurs as reduced DHW exposure with a risk of slowed adaptation in thermal tolerance and occasional shading failure.
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) Increase thermal Managed selection, Narrow rolling Genetic model tolerance via managed breeding, window for genetic adaptation genetic manipulation, calculating the assisted gene flow DHW value in hX(τ)
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Bayesian Network Analysis Simulation of all intervention strategy options over a range of conditions and time, along with environmental stochasticity in DHWs, results in a distribution of possible outcomes for total coral cover, the model's focal evaluation metric. The committee demonstrates the use of Bayesian network analysis to convert the range of outputs from the dynamic model to a network of conditional probabilities to inform decision making.
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E: Reef shading and AGF are used without management of local stressors. local environmental conditions, and reef ecosystem dynamics.
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These priorities include improved ways to identify, measure, and monitor fitness parameters of corals; greater understanding of factors that contribute to stress tolerance and associated tradeoffs for corals; and measuring the impact of interventions on demographic processes within reef ecosystems. Research on Fundamental Coral Reef Biology Effective intervention approaches for reefs require an improved understanding of which factors underpin coral health and how these lead to reef resilience at scale.
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• Identifying host, symbiont, and microbial populations at restora tion sites to ensure that treatments or manipulations aimed at improving coral physiological performance can achieve recovery goals. • Assessing in a site-specific manner the benefits, risks, and chances of success for implementing environmental interventions.
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• Using iterative model design to reduce uncertainties and improve model predictions to increase confidence in the decision support framework. TROPICAL WESTERN ATLANTIC AND CARIBBEAN CASE STUDY The committee was tasked with assessing coral intervention strategies and their ability to meet objectives for sustaining coral reefs in the Caribbean and tropical western Atlantic.
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These attributes include generally poor reef conditions, intrinsic vulnerability, high interconnectedness, low diversity of coral and algal symbionts, high environmental variability across the region, and persistent and destructive disease outbreaks. The social attributes include a relatively widespread and growing network of coral restoration practitioners located in a small (compared to the Indo-West Pacific)
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Conclusion: Coral reef managers in the tropical western Atlantic/ Caribbean region have a variety of interventions available to them depending on the localized management context and the specific objectives of stakeholders and decision makers. Available actions include leveraging existing restoration and propagation infrastructure, increasing sexual reproduction and genetic diversity of corals (managed breeding, gamete and larval capture and seeding, coral cryopreservation)
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These rapidly developing new interventions do not replace the need for direct management of local stressors. Recommendation: The ongoing management and restoration efforts in the Caribbean provide a strong foundation on which to implement newly emerging interventions designed to increase the resilience of individual corals and coral populations.
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