Climate change threatens well-being from the ocean by disrupting both marine and economic systems, yet its global implications remain unclear. This research introduces the Blue Well-being Index (BWI) to assess and predict the performance of ocean-derived well-being for 143 coastal countries under different climate change scenarios. The findings underscore the importance of coordinated international mitigation and ocean-conservation efforts to safeguard human well-being and ocean health.

Results

Historical assessments reveal that the global average BWI score showed modest improvement, rising from 44.8 in 2000 to 50.5 in 2021. However, blue well-being performance varied substantially across countries, with only a few demonstrating consistently high outcomes. Most countries demonstrated poor performance, scoring below 60, which indicates a concerning state. While nations such as the United Kingdom, United States, Australia, Canada, Norway, and Japan achieved relatively high BWI scores, Africa generally consistently scored below the global mean.

Global blue well-being increased over the past two decades (2000–2021)

Considerable disparities in BWI scores were observed across coastal country groups. High-income countries (HICs) demonstrated substantially higher BWI scores than low-income countries (LICs), likely due to a stronger capacity for marine resource utilisation, more robust economic and governance systems, and greater investments in marine education and research. Notably, between 2000 and 2021, approximately 33% of Oceania coastal countries experienced BWI declines, followed by Asia (15%) and Africa (11%). Conversely, the United Arab Emirates showed the largest increase in BWI score, rising from 51.7 in 2020 to 74.5 in 2021.

Synergies among blue well-being dimensions and indicators across countries

The global average BWI synergy score fluctuated near zero, displaying substantial spatial heterogeneity. Positive synergy indicates the co-improvement of indicators, while negative values reflect overall decline. Only a select group of nations, notably the United States and China, demonstrated strong positive synergy. In contrast, the UK, most African countries, and several Latin American and Middle Eastern nations exhibited negative synergy. Individual indicators such as clean seawater, marine conservation, and shipping and trade emerged as key positive drivers of BWI synergy.

Projected changes in blue well-being under climate change

Future projections under high-emission scenarios (SSP5-8.5) indicate disproportionate losses across the 143 countries. Under this scenario, global BWI is projected to decline by approximately 9% by 2100, with adverse effects in nearly 90% of coastal countries. Conversely, under the climate-mitigation SSP1-2.6 scenario, projections indicate that the world could achieve an overall approximately 11% improvement in BWI across 76% of coastal nations. Shifting from SSP5-8.5 to SSP1-2.6 could recover approximately 19.8% of the global blue well-being loss.

Discussion

Despite the global upward trend in historical BWI scores, regional disparities pose a fundamental challenge to achieving equitable blue well-being. High and upper-middle-income countries consistently achieve higher scores, while low and lower-middle-income countries face a dual burden: low BWI scores combined with negative synergy. This advantage for wealthier nations stems from their greater economic capacity to invest in social protection systems, marine education, and ocean conservation programmes. For instance, the United Arab Emirates has successfully launched targeted management plans such as UAE Vision 2030 to enhance local blue well-being.

Methods

The BWI framework integrates four dimensions—social, economic, natural, and subjective well-being—captured by 16 indicators including marine employment, biodiversity, and mental health. A fuzzy logic model was applied to synthesise these indicators into a standardised country-level composite score ranging from 0 to 100. The research assessed how climate stressors, including global warming, sea-level rise, tropical cyclones, and coastal flooding, alter trajectories under alternative socioeconomic and emission pathways.

Blue Well-being Index (BWI)

The BWI comprises 13 objective well-being indicators and 3 subjective well-being indicators. Objective measures cover basic material requirements, employment, and health, while subjective indicators encompass social support, freedom to make life choices, and positive emotions. Because global coastal-specific happiness data is absent, these measures were calculated by weighting country-level data from the World Happiness Report by the proportion of the population living within 50 km of the coast.

SSP-RCP scenarios

The research evaluated four Shared Socio-economic Pathways (SSP) and Representative Concentration Pathways (RCP) to assess the interactive effects of global climate change and socioeconomic development. These include SSP1-2.6 (sustainable pathway), SSP2-4.5 (middle of the road), SSP3-7.0 (regional rivalry), and SSP5-8.5 (fossil-fueled development). These combinations span a wide range of future society change and forcing pathways to allow for direct comparability across studies.