Multi-level contributions of blue-green spaces to social capital development among older adults: An empirical study in Guangzhou

Population aging exacerbates challenges such as deteriorating health, social isolation, and resource constraints. While blue-green space plays a critical role in promoting healthy aging and social capital, research gaps remain in understanding multilevel mechanisms. Based on 864 questionnaires from older adults in Guangzhou, China, this study analyses the multilevel impact of blue-green space on social capital accumulation at the individual, community, and district levels. The results show that: (1) Few older adults possess high social capital, and its spatial patterns diverge from blue-green coverage; high-quality and equitable green spaces better foster social capital, (2) Social capital formation is multilevel. At the individual level, gender, health, income, space use intensity, and accessibility are positively associated with social capital, while higher education, exercise intensity, and space satisfaction show inverse associations. At the community level, per capita blue-green space area and house prices are positively associated with social capital, but negative associations with community type and facility numbers reflect resource inequality. At the district level, ecological investment, blue-green coverage, and the aging ratio are positively associated with social capital formation. (3) Uneven resource distribution across levels amplifies the impacts of education, income, and health across regions. Based on findings, we recommend that local governments prioritize filling green space gaps in older and peripheral communities to improve the vitality and accessibility of urban open spaces. Attention should be given to older adults with lower socioeconomic status by strengthening participation and governance, and advancing district-level ecological–health integration to transform blue-green coverage into social capital. • Blue-green space resources shape social capital through multi-level mechanisms. • Individual socioeconomic and behavioral traits dominate social capital differences. • Blue-green space layout and location value key to driving community social capital. • Ecological construction, green coverage, and aging influence district social capital. • Cross-level resource inequality amplifies individual differences in nested systems.