Vitamin N: Benefits of Different Forms of Public Greenery for Urban Health

TL;DR

This study introduces a new classification of urban greenery distinguishing on-road from off-road greenery, demonstrating that on-road greenery is more strongly associated with improved health outcomes and could lead to significant healthcare cost reductions.

Contribution

The paper presents a novel methodology combining aerial imagery, street view data, and accessibility estimates to measure on-road greenery and links it to health outcomes, highlighting its importance over traditional greenery metrics.

Findings

On-road greenery is more strongly linked to better health than traditional measures.

Increasing on-road greenery could reduce healthcare costs by up to a33.15 million annually.

Official greenery metrics may underestimate the health benefits of accessible urban greenery.

Abstract

Urban greenery is often linked to better health, yet findings from past research have been inconsistent. One reason is that official greenery metrics measure the amount or nearness of greenery but ignore how often people actually may potentially see or use it in daily life. To address this gap, we introduced a new classification that separates on-road greenery, which people see while walking through streets, from off-road greenery, which requires planned visits. We did so by combining aerial imagery of Greater London and greenery data from OpenStreetMap with quantified greenery from over 100,000 Google Street View images and accessibility estimates based on 160,000 road segments. We linked these measures to 7.45 billion medical prescriptions issued by the National Health Service and processed through our methodology. These prescriptions cover five conditions: diabetes, hypertension, asthma, depression, and anxiety, as well as opioid use. As hypothesized, we found that green on-road was more strongly linked to better health than four widely used official measures. For example, hypertension prescriptions dropped by 3.68% in wards with on-road greenery above the median citywide level compared to those below it. If all below-median wards reached the citywide median in on-road greenery, prescription costs could fall by up to {\pounds}3.15 million each year. These results suggest that greenery seen in daily life may be more relevant than public yet secluded greenery, and that official metrics commonly used in the literature have important limitations.