Adaptation strategies for coral reef ecosystems in Small Island Developing States: Integrated modelling of local pressures and long-term climate changes
Introduction
Global population growth and increasing human impacts on ecosystems raise questions around the functionality and capability of marine ecosystems to provide adequate services which support social wellbeing to an acceptable level (Santos-Martín et al., 2013). Variations in the functioning and composition of marine ecosystems and the resultant threats and opportunities of ecosystem changes can significantly affect human well-being (IPCC, 2014). According to the Millennium Ecosystem Assessment (MEA, 2005), in many instances, the flow of ecosystem services is being impaired as a direct result of changing climate conditions as well as non-climatic pressure. Within several decades, this current trend will result in the alteration of all ecosystems and may have severe negative impacts on ecosystem services and human well-being (Colls et al., 2009). Therefore, it is of paramount importance to identify, assess, and understand the provision of ecosystem services, to put more planning efforts toward improving the health and resilience of the supporting ecosystems. However, recommending management strategies or adaptation planning should incorporate the uncertainties in future social and natural land conditions under different climate change pathways (Comte and Pendleton, 2018).
Small Island Developing States (SIDS) are among the most vulnerable communities, being highly dependent on services from coastal ecosystems. SIDS are a group of 57 small island countries listed by the United Nations Department of Economic and Social Affairs (UNDESA) (Spector et al., 1994) that share similar sustainable development challenges despite specific cultural and geographical differences (Hay, 2013). A range of factors, namely, remoteness, limited public education services and community awareness, being highly exposed to natural extreme events and disasters, and limited accessible funds are considered the most important challenges for SIDS. Inopportunely, coral reefs are also particularly vulnerable to multiple local-based activities and pollution, and climatic distresses (Hughes et al., 2017; Ateweberhan et al., 2013). Globally, coral reefs provide services and livelihoods for millions of people (Hughes et al., 2017). For SIDS in particular, coral reefs are among key ecosystems for sustaining livelihoods (Martin et al., 2017) and, together with mangroves, important for coastal protection against extreme weather events (Hughes et al., 2017). Thus, planning for SIDS communities under rapidly changing and uncertain non-climatic and climatic conditions requires a realistic and long-term evaluation of impacting factors and potential management interventions for minimising the risks to these ecosystem services and that are effective and appropriate (Betzold, 2015; Robinson, 2017). Tanna Island, Vanuatu, was selected as a case study region since it represents a typical microcosm of Pacific-SIDS geography and human settlements that are highly reliant on ecosystem services. It is to be noted that this study was undertaken as a part of an extensive project titled “EcoAapt in the Pacific” that aimed to identify appropriate adaptation interventions in the coastal zones of Pacific island states and territories in the face of rapidly changing climate and ongoing capital-intensive developments.
However, assessments of erratic, multidimensional and complex systems, such as coral reef ecosystems (Harvey et al., 2018) that exhibit a high level of uncertainty (Hoegh-Guldberg et al., 2019), mandates the employment of an integrated approach (Hafezi et al., 2018). Moreover, each assessment requires a customised procedure that can cater to the specific needs and characteristics of each system (Voinov and Shugart, 2013). Particularly, environmental systems, which are under constant changing climate conditions, are more likely to yield reliable outcomes when an integrated modelling approach is exploited (Hafezi et al., 2018). Besides, assessments of the socio-economic components of the coral reefs’ health and resilience system, as well as region-specific characteristics, opportunities, and limitations mandate the elicitation of local stakeholders’ knowledge in conjunction with other inputs, in order to derive reliable equations and probability distributions (Hoegh-Guldberg et al., 2019). Accordingly, this study required a modelling approach that is capable of taking into account the following aspects: 1) multiple factors that are conventionally dealt with by different disciplines but that account for a wide range of climate change-induced risks, and an assessment of the central ecosystem; 2) integrative evaluations that combine both quantitative and qualitative types of data; 3) understanding of the causal relationship between the multiple stressors and reef health and resilience; and 4) effective treatment of the modelling complexities and uncertainties associated with the array of social and environmental factors. In other words, adoption of an advanced and practical approach and strategy was a mandate rather than an option to incorporate different types of qualitative and quantitative multidisciplinary data as well as to include a proper description and quantification of uncertainty in the modelling and assessment processes. For this purpose, an innovative participatory and integrated modelling strategy was to be developed that is highly efficient in integrating local and long-term climate change pressures under the specific characteristics of SIDS.
Recently, the Bayesian Network (BN) technique has gained researchers attention (Kerebel et al., 2019) and been employed as the main modelling platform in different environmental studies such as ecosystems and ecological assessments (Smith et al., 2018), water management (Hallouin et al., 2018; Phan et al., 2016) and ecosystem services modelling (Zeng and Li, 2019). Landuyt et al. (2013) conducted a SWOT analysis of modelling techniques for ecosystem services and suggested the BN methodology as well suited for ecosystem-related assessment, despite some limitations and weaknesses. Similarly, Uusitalo (2007) identified the BN as an effective approach for complex environmental modelling and management problems having high specificity requirements. However, the key attributes for an adequate assessment of coral reefs health and resilience necessities the BN model to be quantified using multidisciplinary, data-induced, evidence-based, and expert-driven approaches. In light of these requirements, this study requires to further advance previous BN modelling frameworks for reef management, such as Gilby et al. (2016) and Brown et al. (2017), by integrating long term climate scenarios with local pressures from increasing human use and land-management. Additionally, the exploitation of structural analysis in a sequential integration procedure coupled with other modelling techniques in a stepwise manner enables modelling needs and requirements to be addressed more effectively (Suprun et al., 2018).
This paper presents a novel probabilistic scenario-based modelling approach using hybrid exploitation of the BN and structural analysis techniques using qualitative and quantitative data to investigate the long-term impacts of climatic and non-climatic pressures, together with a range of management response strategies, on the health and resilience of coral reefs for the time horizon of 2070. While the resilience of coral reefs represents the recovering capability of reef systems to recover towards a coral-rich state from either climatic or non-climatic pressures disturbance as a result of extreme events (Hughes et al., 2017). In addition, reef system resilience can be referred to their resisting or maintaining capacity against shifting from the morphological diversity towards single coral morphology or algal dominance (Scott et al., 2015). However, the health and resilience of coral reefs is relative to the coral cover in the study zone in this study. The Representative Concentration Pathways (RCP)s (IPCC, 2014) were used as the basis for different climatic scenarios to explore the implications of climate change impacts.
Section snippets
Case study location
Tanna is a relatively small island (550 km2) in Tafea Province, State of Vanuatu (in the Melanesian Pacific islands), in the South Pacific Ocean, with a rapidly increasing population largely living in traditional village communities (Buckwell et al., 2019). (Elliff and Kikuchi, 2017). Coral reefs are subject to multiple anthropogenic pressures, which currently deliver vital ecosystem services to Tanna’s community, including improving the local economy through tourist attraction (Mackay et al.,
Modelling approach
The modelling approach and procedure were formulated by the multidisciplinary team of experts having skillsets from diverse and independent research fields including marine biology, coastal systems, climate change, systems modelling and risk assessment. Importantly, it should be noted that these experts had adequate knowledge of the study area and context since they were previously involved in a research project focusing on climate change resilience analysis and ecosystem and socio-economic
Delineation
Formation of the modelling team, formulation of the modelling approach and the definition of modelling scope including regional, temporal, and interdisciplinary boundaries were established throughout the delineation step. An extensive review of the literature on coral reef health and resilience was conducted to identify the key variables and stressors (see Supplementary File A).
Following this, a list of 23 key variables was selected from a list of variables (known as nodes in BN modelling)
Codifying layers and data collection
The following sub-sections outline the various nodes and supporting evidence used to quantify the model by completing nodes’ relationship functions or CPTs within the four DPSI layers. Readers are referred to Supplementary Files A and B for a detailed discussion of the node definitions and supporting evidence.
Scenario setting
Once the model quantification was accomplished, scenario settings were defined to conclude the modelling procedure with the last phase. Scenario-based analyses aimed at predicting the health and resilience of coral reefs in response to the management strategies and prospective scenarios covering both direct and indirect anthropogenic as well as climatic disturbances by 2070. Scenario nodes’ states were changed to compare the target node of persisting or declining coral reef health and
Results and discussion
By the completion of the model and the accomplishment of meaningful scenario settings, the health and resilience conditions under each scenario for all four RCPs were projected. Scenario predictions showed the probability of both persisting and declining states. The scenario predictions show the probability of ecosystem condition for the time horizon of 2070. The results of this scenario-based modelling can provide decision-makers and stakeholders with a more holistic view and new insights into
Conclusion
This study explored the long-term perspective of the future health and resilience condition of coral reefs under different combinations of management strategies and under four climate change RCPs. A BN model was developed through a systematic approach by following a stepwise modelling procedure. Subsequently, twelve scenario settings were defined based on the effectiveness or the extent of management strategies, climate change trajectories, and future population projections. The presented
CRediT author statement
Mehdi Hafezi: Conceptualization, Literature review, Data curation, Methodology, Software, Writing- Original draft preparation.
Oz Sahin: Data curation, Methodology, Investigation, Writing- Original draft preparation, Reviewing and Editing.
Rodney A. Stewart: Methodology,Validation, Writing- Original draft preparation, Reviewing and Editing.
Rod M. Connolly: Data curation, Validation, Reviewing and Editing.
Brendan Mackey: Reviewing, Editing and Supervision.
Daniel Ware: Reviewing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This research was conducted as part of the EcoAdapt Project which is funded by a private charitable trust that wishes to remain anonymous. The donor had no input or influence on any aspect of the design, implementation, analyses or documentation of the research reported here.
References (117)
- et al.
Bayesian networks in environmental modelling
Environ. Model. Softw
(2011) - et al.
Best practices for conceptual modelling in environmental planning and management
Environ. Model. Softw
(2016) - et al.
Climate change impacts on coral reefs: synergies with local effects, possibilities for acclimation, and management implications
Mar. Pollut. Bull.
(2013) - et al.
Assessing interactions of multiple stressors when data are limited: a Bayesian belief network applied to coral reefs
Glob. Environ. Chang.
(2014) - et al.
Management strategies for coral reefs and people under global environmental change: 25 years of scientific research
J. Environ. Manag.
(2018) - et al.
Impacts of nutrient enrichment on coral reefs: new perspectives and implications for coastal management and reef survival
Curr. Opin. Environ. Sustain.
(2014) - et al.
Ecosystem services provided by coral reefs in a southwestern Atlantic Archipelago
Ocean Coast Manag.
(2017) - et al.
The role of fish and fisheries in recovering from natural hazards: lessons learned from Vanuatu
Environ. Sci. Policy
(2017) Effects of terrestrial runoff on the ecology of corals and coral reefs: review and synthesis
Mar. Pollut. Bull.
(2005)- et al.
A Bayesian Belief Network to assess rate of changes in coral reef ecosystems
Environ. Model. Softw
(2016)
A review of the application and evolution of the DPSIR framework with an emphasis on coastal social-ecological systems
Ocean Coast Manag.
Environmental impacts of tourism in the Gulf and the Red Sea
Mar. Pollut. Bull.
Integrated assessment and modelling: overview and synthesis of salient dimensions
Environ. Model. Softw
Snorkelling and trampling in shallow-water fringing reefs: risk assessment and proposed management strategy
J. Environ. Manag.
Food security versus environment conservation: a case study of Solomon Islands’small-scale fisheries
Environ. Dev.
People and the changing nature of coral reefs
Reg. Stud. Mar. Sci.
Landscape aesthetic modelling using Bayesian networks: conceptual framework and participatory indicator weighting
Landsc. Urban Plan.
Spatial vulnerability assessment of anchor damage within the great barrier reef world heritage area, Australia
Ocean Coast Manag.
The construction of causal networks to estimate coral bleaching intensity
Environ. Model. Softw
A review of Bayesian belief networks in ecosystem service modelling
Environ. Model. Softw
Study of impact factors of willingness to pay regarding water reserve of South-to-North Water Diversion Project in Beijing based on Bayesian network model
J. Clean. Prod.
Applications of Bayesian belief networks in water resource management: a systematic review
Environ. Model. Softw
Parameterisation and evaluation of a Bayesian network for use in an ecological risk assessment
Environ. Model. Softw
Framework to assess sources controlling soil salinity resulting from irrigation using recycled water: an application of Bayesian Belief Network
J. Clean. Prod.
Artificial surf reefs: a preliminary assessment of the potential to enhance a coastal economy
Mar. Policy
Modelling the dynamics of coral reef macroalgae using a Bayesian belief network approach
Ecol. Model.
Assessing the effects of sediments and nutrients on coral reefs
Curr. Opin. Environ. Sustain.
A comparison of two sensitivity analysis techniques based on four bayesian models representing ecosystem services provision in the Argentine Pampas
Ecol. Inf.
A spatial temporal decision framework for adaptation to sea level rise
Environ. Model. Softw
Spatial Bayesian Network for predicting sea level rise induced coastal erosion in a small Pacific Island
J. Environ. Manag.
A Bayesian belief network modelling of household factors influencing the risk of malaria: a study of parasitaemia in children under five years of age in sub-Saharan Africa
Environ. Model. Softw
Operationalising ecosystem service assessment in bayesian belief networks: experiences within the OpenNESS project
Ecosyst. Serv.
The role of ecosystems in coastal protection: adapting to climate change and coastal hazards
Ocean Coast Manag.
The effects of trampling on Hawaiian corals along a gradient of human use
Biol. Conserv.
Applications of Bayesian network models in predicting types of haematological malignancies
Sci. Rep.
Projected sea surface temperatures over the 21 st century: changes in the mean, variability and extremes for large marine ecosystem regions of Northern Oceans
Elementa: Sci. Anthropocene
Ocean acidification causes bleaching and productivity loss in coral reef builders
Proc. Natl. Acad. Sci.
Ocean acidification and warming will lower coral reef resilience
Glob. Chang. Biol.
Climate Variability, Extremes and Change in the Western Tropical Pacific: New Science and Updated Country Reports (Pacific-Australia Climate Change Science and Adaptation Planning Program Technical Report)
Climate variability, extremes and change in the western tropical pacific: new science and updated country reports (pacific-Australia climate change science and adaptation planning program technical report)
Assessing the Effectiveness of Local Management of Coral Reefs Using Expert Opinion and Spatial Bayesian Modeling
PLoS ONE
Repeat bleaching of a central Pacific coral reef over the past six decades (1960–2016)
Commun. Biol.
GeNIe, decision-theoretic methodology
Adapting to climate change in small island developing states
Clim. Change
Effects of human population density and proximity to markets on coral reef fishes vulnerable to extinction by fishing
Conserv. Biol.
Tracing the influence of land-use change on water quality and coral reefs using a Bayesian model
Sci. Rep.
Thermal stress and coral cover as drivers of coral disease outbreaks
PLoS Biol.
Social benefit cost analysis of ecosystem-based climate change adaptations: a community-level case study in Tanna Island, Vanuatu
Clim. Dev.
Vanuatu climate futures online tool the Commonwealth scientific and industrial research organisatio and Bureau of Meteorology
Reefs at Risk Revisited
Cited by (15)
How Bayesian networks are applied in the subfields of climate change: Hotspots and evolution trends
2024, Environmental Modelling and SoftwareTechnology for environmental management in Small Island Developing States: the case of Bahrain
2022, Current Opinion in Environmental SustainabilityCitation Excerpt :Spatial simulation modeling and Geographic Information Systems (GIS)-based techniques can be used to predict long-term impacts of climate change on health and resilience of marine ecosystems. Hafezi et al. [21] discussed an integrated modeling approach to predict the risks to the health and resilience of coral reef ecosystem in a Pacific SIDS, and possible adaptation and mitigation strategies. Argyroudis et al. [22•] argued that digital technologies can enhance climate change resilience of major infrastructure such as energy and transport systems.
Rapid vulnerability assessment of Pacific sardine (Sardinops sagax) fisheries facing climate change in Mexico
2022, Progress in OceanographyCitation Excerpt :According to several authors, plans to adapt both industrial and small fisheries to climate change require integrated efforts to analyze, model, and agree upon legal measures associated with temporal space use and promote governance with stakeholders of the activity (e.g., Salvadeo et al., 2021). The implementation of new practices is the most important aspect, and sectoral/community work that applies diverse techniques, such as the systematic revision of published literature, surveys, workshops, and academic encounters, will be essential (e.g., Shaffril et al. 2017; Le Cornu et al. 2018; Hafezi et al. 2020). The participation of work groups that include stakeholders from all sectors related to the Pacific sardine fishery can be used to develop an integrated vision of the academic, industrial, and social perspective regarding the future of the fishery in the country.
The tropical Pacific Oceanscape: Current issues, solutions and future possibilities.
2021, Marine Pollution BulletinEvaluating coral reef ecosystem services outcomes from climate change adaptation strategies using integrative system dynamics
2021, Journal of Environmental ManagementCitation Excerpt :Lastly, the SD modelling stage investigated the nexus between environmental and economic values under different combinations of management or adaptation strategies over a long-term period, namely, the 2020–2070 year period. This paper focuses on reporting the SD modelling procedures and results as this novel component of the three-stage procedure, and the first two stages and related modelling techniques were reported in Hafezi et al. (2019, 2020). The outputs of the BN modelling were used to quantify the SD model variables of the model, where the existing data and information were insufficient.
A framework for complex climate change risk assessment
2021, One EarthCitation Excerpt :Including climate change responses as potential drivers of risk expands the scope of risk assessment to accommodate positive and beneficial outcomes, not just negative, adverse ones. This is vital for making informed responses more transparent and actionable within complex social decision-making structures,54,64 where stakeholders attach different weights to the diversity of positive and negative consequences that can arise from both action and inaction. Third, risk assessment needs to include interactions among multiple risks, not just among the determinants of a risk.