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Climate change poses significant threats to wellbeing and livelihoods of people and the ecosystems in many Small Island Developing States (SIDS). Adaptation solutions must counteract these threats while also supporting development in vulnerable SIDS. Suitable options need to ensure that connections between the social, economic, and environmental dimensions of socio-economic systems are defined in a way that can support how decisions are made (and by whom) and how these can impact on other parts of these systems. This is particularly important in many Pacific SIDS, where communities practise customary natural resource management and continue to rely on local natural resources. In this study, we model the anticipated impacts of climate change and the benefits of the ecosystem-based adaptation (EbA) approaches on community wellbeing in Vanuatu. To do this, we applied participatory and expert elicitation methods to develop a Bayesian network model, which was designed to evaluate community wellbeing responses at four explicit spatial scales. The model includes both acute and chronic impacts of climate change, the impact of coral bleaching, and the potential loss of Vanuatu’s fringing coral reefs. The model predicts that all proposed EbA interventions will have a positive impact on wellbeing in all four locations to some degree, by either directly improving the integrity of Vanuatu’s ecosystems or by protecting these ecosystems as a positive spill-over of related actions. Significantly, it also predicts that if climate change exceeds 1.5 °C of warming, the costs of achieving the same level of wellbeing are increased.

Coastal freshwater supply and demand systems are expected to be significantly affected by changes to both climatic and non-climatic drivers over coming decades. Adapting to these changes to secure adequate freshwater to meet the rising demands of socio-economic development has become a critical task for decision-makers. Whilst a range of adaptation options may be available, the complexity and interconnectedness of water resource systems make it challenging to identify which options are likely to be most feasible and effective. Here, we present a Bayesian decision network (BDN) that was co-developed with local experts to identify appropriate adaptation options for freshwater management under both current and likely future conditions in the Da Do Basin of coastal Vietnam. Potential adaptation options were prioritised according to cost-effectiveness based on relative costs incurred and relative utilities delivered across a range of future scenarios. The BDN model indicated that cost-effectiveness of adaptation options varied between future scenarios. Constructing pumping stations was the most cost-effective option under climate change scenarios, whilst a higher water price was the most cost-effective option under non-climatic changes. Under combined climatic and non-climatic changes, constructing pumping stations in combination with increasing water prices provided the most cost-effective option. The model affords an opportunity for decision-makers in the Da Do Basin to prioritise and evaluate appropriate and feasible adaptation actions under different scenarios with respect to multiple drivers.

Coastal freshwater wetlands are amongst the world’s most modified but poorly researched ecosystems and some of the most vulnerable to climate change. Here, we examine vegetation resilience in coastal wetlands of subtropical Australia to altered salinity and flooding regimes likely to occur with climate change. We conducted field surveys and glasshouse experiments to examine plant diversity and regeneration responses of understorey and canopy species across four habitats. Vegetation composition, but not richness, varied between seaward and inland habitats while soil seed bank diversity was greatest in more inland sites. Experimental salinity and flooding treatments strongly influenced emergence from seed banks with most species germinating under fresh, waterlogged conditions and very few in saline treatments. Composition of emerging seedling assemblages was similar across habitats and treatments but differed considerably from the extant vegetation, indicating a relatively minor role of soil seed banks in sustaining current vegetation structure in this wetland. An exception to this was Sporobolus virginicus (marine couch) which was common in both the vegetation and seed banks suggesting a high capacity for this species to re-establish following disturbances. Seedlings of dominant canopy species also reacted strongly to increased salinity treatments with decreased survivorship recorded. Overall, our findings suggest a high probability of constrained vegetation regeneration in this wetland in response to key projected climate change disturbances with implications for vegetation diversity at a landscape scale including declines in the extent and diversity of more landward vegetation communities and expansion of salt-tolerant marshes dominated by Sporobolus virginicus.