The Lancet Planetary Health, April 2025

A health impact assessment of progress towards urban nature targets in the 96 C40 cities

Theory and empirical evidence support a positive relationship between nature contact and human health. The biophilia hypothesis states that humans have an innate affinity towards nature, including greenspaces (eg, parks and trees) and blue spaces (eg, rivers and lakes), which were once synonymous with food, water, and shelter. Greenspace is positively associated with general health and physical activity and negatively associated with adverse birth outcomes, cardiovascular events, all-cause mortality, depression and anxiety, and lung and prostate cancer.

Although fewer studies address the health benefits of urban blue space compared with urban greenspace, systematic reviews support the association between urban blue space and decreased obesity, decreased all-cause mortality, and improved general and mental health. Blue space and greenspace are hypothesised to benefit health through common pathways, including increased social interaction and physical activity and decreased stress and environmental harms.