The health benefits of urban green spaces are numerous and well known, such as increased life expectancy, reduced mental illness and improved cognitive function. But the answer to the problem of the exact surface area of green space required to promote population health remains open.
What does the 3-30-300 rule mean?
Recent research carried out by ISGlobal, an organization supported by the “la Caixa” Foundation, investigated the relationship between better mental health and the 3-30-300 principle of green spaces. According to this general rule, everyone must be able to see at least three trees from their home, have 30% tree cover in their neighborhood and live no more than 300 meters from the nearest park or green space.
Results from this study reveal that full adherence to the 3-30-300 green space rule is significantly associated with improved mental health, reduced medication use and fewer consultations with a psychologist, although this relationship is only statistically significant.
Results from this survey show that only 4.7% of those taking part in the survey meet all three aspects of the green space rule. Thus, just over 43% of the respondents had at least three trees within a radius of 15 meters around their home, 62.1% had a significant green area within a radius of 300 meters, and 8.7% of the respondents lived in a relatively green area. On the other hand, just under 22.4% benefited from all these conditions.
3 trees for each household.
The first rule states that everyone must be able to spot at least three trees from their home. Recent research demonstrates the importance of a nearby, and especially visible, green environment for mental health and well-being. During the COVID-19 pandemic, people have often been confined to their homes or immediate neighborhoods, giving even greater importance to nearby trees and other green spaces, in gardens and along streets.
30% tree cover in each quarter.
Studies have shown a connection between urban forest cover and, for example, cooling, better microclimate, mental and physical health and possibly also reduced air pollution and noise. Many of the world’s most ambitious green cities, including Barcelona, Bristol, Canberra, Seattle and Vancouver, have set themselves the goal of achieving 30% green cover. At the neighborhood scale, 30% should be a minimum, with cities striving to achieve even higher canopy coverage where possible. Where it is difficult for trees to grow and thrive, for example in dry climates, the target should be 30% vegetation.
300 meters distance between the residence and the nearest green areas.
Numerous studies have highlighted the importance of proximity and easy access to high-quality green spaces that can be used for recreational purposes. A safe 5 minute walk or a 10 minute walk is often mentioned. The European Regional Office of the World Health Organization recommends respecting a maximum distance of 300 meters separating the nearest green area (of at least 1 hectare).
This encourages the use of green spaces for recreational purposes, which has positive consequences for physical and mental health. It will of course be important to work with the local context, as the needs in, for example, dense urban areas will be different than in denser urban areas. But here, too, the focus must be on providing access to high-quality urban greenery, for example in the form of linear green areas that function as cycle and pedestrian paths. Applying the 3-30-300 rule will improve and expand the local urban forest in many cities, thereby promoting health, wellness and resilience.