TLDR: A new study reveals that ‘on-road greenery’ – the vegetation people see daily on streets – is more strongly linked to better health outcomes, including lower prescription rates for conditions like hypertension, asthma, depression, and anxiety, than traditional measures of green space. The research, based on data from Greater London and NHS prescriptions, suggests that integrating visible greenery into daily routines could lead to substantial health improvements and cost savings, highlighting limitations of current urban greenery metrics.
Urban environments are increasingly recognized for their impact on public health, and green spaces are often highlighted as a key factor for well-being. However, past research on the health benefits of urban greenery has shown inconsistent results. A new study, titled “Vitamin N: Benefits of Different Forms of Public Greenery for Urban Health”, sheds light on why this might be the case and proposes a more effective way to measure greenery’s influence.
The research, conducted by Sanja Šćepanović, Sagar Joglekar, Stephen Law, Daniele Quercia, Ke Zhou, Alice Battiston, and Rossano Schifanella, suggests that traditional methods of measuring urban greenery often fall short. Metrics like the Normalized Difference Vegetation Index (NDVI) or those based on World Health Organization (WHO) and Natural England (NE) targets tend to measure the sheer amount of green space or its proximity, but they often fail to consider how often people actually see or use this greenery in their daily lives. For instance, these measures might include private gardens, farmlands, or large parks that are difficult to access or not part of routine commutes.
To address this gap, the researchers introduced a novel classification system, distinguishing between “on-road greenery” and “off-road greenery.” On-road greenery refers to the vegetation people encounter while walking or moving through streets, such as street trees, hedges, and green facades. Off-road greenery, on the other hand, includes parks and other public green areas that typically require a planned visit.
The study combined various data sources for Greater London, including aerial imagery, OpenStreetMap data, and over 100,000 Google Street View images, along with accessibility estimates for 160,000 road segments. This comprehensive approach allowed them to quantify both types of greenery more accurately. They then linked these greenery measures to 7.45 billion medical prescriptions issued by the National Health Service (NHS) for six common conditions: diabetes, hypertension, asthma, depression, anxiety, and opioid use.
The findings were striking. As hypothesized, on-road greenery was consistently and more strongly linked to better health outcomes compared to the four widely used official measures. For example, wards with on-road greenery above the citywide median saw a 3.68% drop in hypertension prescriptions compared to those below the median. The study estimated that if all wards currently below the median level of on-road greenery were to reach that level, it could lead to a reduction of approximately 37.25 million prescriptions annually, saving the NHS up to £3.15 million each year.
In contrast, the traditional greenery metrics showed inconsistent or even adverse associations with prescription rates. Some official measures were linked to increased prescriptions for certain conditions, which the authors suggest could be due to these metrics including inaccessible green areas or large, mown parklands that might not offer sufficient social or environmental benefits.
This research highlights that the visibility and routine exposure to greenery are crucial for its health benefits. It suggests that greenery seen incidentally during daily activities may be more impactful than public but secluded green spaces. The implications for urban planning are significant: instead of solely focusing on the quantity or general proximity of green spaces, urban planners and public health professionals should prioritize integrating greenery into the street network, making it a visible and accessible part of daily life for residents.
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While the study was observational and has limitations, such as not fully capturing individual mobility or socio-spatial inequalities, its findings provide actionable insights for designing healthier, greener cities that promote well-being more effectively and equitably.
