The sustainability of small island developing states (SIDS) of the Caribbean is fragile because of island size and topography, limited resources, population growth, natural disasters, and climate change. Current and projected sustainability in 2050 were assessed within the framework of the water–energy–food (WEF) nexus for 10 of 16 SIDS with the best databases. Values for each WEF sector below either Falkenmark indicators or regional averages were considered unsustainable (failing) for that sector. Overall, SIDS were considered unsustainable if they failed at least two of three sectors. Projected water sustainability for 2050 was based on population growth and climate change effects on precipitation and per capita water availability. All SIDS failed the food sector, and four failed the energy sector. Water was considered the ultimate control for long-term sustainability. Five SIDS currently fail the water sector, but all but the largest two SIDS are likely to fail this sector by 2050. The role of poor governance and associated lack of long-term planning for population growth, disasters, and climate change, adaptative management strategies, infrastructure investment with an emphasis on nature-based solutions, decentralized energy grids emphasizing renewable energy, and local food production are clearly impediments for reaching sustainability goals for Caribbean SIDS.

The 10 Small Island Developing States (SIDS) of the Caribbean in this study have unsustainable water-energy-food Nexus conditions, with stress becoming more acute via climate change, population demographics and increasing tourist demands. Water resources are limited, and wastewater treatment is inadequate or missing. Nature-based solutions (NBS), especially constructed wetlands, are effective treatment options for all SIDS and have added value for recreation, conservation and product development. On islands with abundant rainfall, NBS treated water adds little to total water resources, but can be important for small scale agriculture. Rainwater harvesting is an important alternative water source for individual households and small communities, but water reuse from tourist infrastructure has the greatest potential for SIDS to reach water sustainability, while protecting coastal waters from sewage pollution. Tourism is a two-edged sword. It swells populations and associated water demand significantly and can degrade coastal waters if wastes are not treated effectively. However, a partnership among the tourist industry, local communities and national government must be given top priority to ensure sustainability of the Water-Energy-Food (WEF) Nexus in the face of progressively increasing tourist numbers and pressures. Effective governance is needed at the island and regional level to develop sound adaptative management approaches for sustainability.