03/06/2025
Welcome back to our 5th and last post from our content series on the '3-30-300' rule in urban green space planning!
”Many working in urban forestry, the planning and management of trees and associated vegetation in urban areas, are familiar with Santamour’s so called ”10–20–30” guideline for urban tree diversity.
As a rule of thumb, he argued, a city’s urban forest composition should not have more than 10% of the same tree species, no more than 20% of a single tree genus and should not exceed 30% of the same family.
It is likely that the simplicity of Santamour’s guideline and its ‘stickiness’ has led to its wide adoption, even when the evidence supporting it was limited.
Early in 2021, this author proposed a new, evidence-based guideline for developing greener, more resilient, and healthier cities, towns, and neighbourhoods, titled the 3–30–300 rule for urban forestry.
The rule states that every resident needs to have
access to the following:
*The 3 trees from every home, school, and place of work*
Every resident in a city, town, or even village should be able to see at least three trees from their home, school, or place of work. These trees should ideally be well-established as fewer large-sized trees impacted resident mental health more positively than a larger number of smaller ones.
*The 30% tree canopy cover in every neighbourhood*
Based on current research, as previously discussed, at the neighbourhood level, a 30% canopy cover should be a minimum, and cities should strive for even higher canopy percentage when possible. Note that the 30% is not at the city level, as this can result, for example, in tree inequity. Studies have shown the importance of proximity and tree canopy in providing cooling and health benefits, primarily at the local level.
*The 300 m from the nearest park or green space*
In line with research and with WHO recommendations, every citizen should have a large public green space within 300 m, approximately a 5-min walk or so, from their home. WHO suggests a public green space of at least 1-ha, but this may sometimes be difficult to achieve. The size of green space is important, as larger parks and other green spaces have been associated with more recreational opportunities and higher preferences, and with higher levels of biodiversity. It is important to realise that public green spaces come in many different forms and shapes.
In Mediterranean cities, for example, treed ‘ramblas’ or walking avenues function as de facto green spaces, even when they are traffic corridors. But it is important that green spaces are of a high quality, allowing for a range of recreational activities, including functioning as social meeting places, and offering opportunities for children’s play. There should also be sufficient trees and vegetation for providing shade.
Since its launch in early 2021, there has been some interest in the 3–30–300 rule from cities and organisations in different countries. Several have formally or informally adopted the rule as part of their urban forestry.
Using the rule provides evidence-based, easy-to-remember targets that link urban trees and green spaces to climate and health benefits. It also allows for benchmarking (that is, monitoring and comparing with peers nationally and internationally) as well as easy monitoring of progress. The rule’s simplicity makes it easy to communicate and can generate interest and support among residents, politicians, businesses, and other key stakeholders. Applying the 3–30–300 rule can help improve and expand the local urban forests in many cities as part of wider programs and policies, and promote health, wellbeing, and resilience.”
That’s it from us on this series, thank you for coming along for the ride 🥰
For more information or sources, please search for the following document: "Evidence-based guidelines for greener, healthier, more resilient neighbourhoods: Introducing the 3–30–300 rule" published by Springer Nature and written by Cecil C. Konijnendijk.
