The paper: Konijnendijk's 3-30-300 rule

The 3-30-300 rule was devised by Cecil Konijnendijk van den Bosch, professor of urban green and director of the Nature Based Solutions Institute in Barcelona. He launched the rule in early 2021 and worked it out in a scientific paper. This page summarises that paper and shows where this map departs from it.

Konijnendijk, C.C. (2023). Evidence-based guidelines for greener, healthier, more resilient neighbourhoods: Introducing the 3–30–300 rule. Journal of Forestry Research 34, 821–830. Published online on 26 August 2022. Open access (CC BY).
doi.org/10.1007/s11676-022-01523-z · full text (PubMed Central)

How it started

On 19 February 2021 Konijnendijk proposed the rule in a LinkedIn post, which was soon taken up by the IUCN Urban Alliance. Cities and organisations had asked him for guidelines for urban green that apply anywhere. He compares the rule with Santamour's well-known 10-20-30 rule for the species diversity of street trees: short, easy to remember and still based on research. The paper in the Journal of Forestry Research is the first scientific publication on the rule.

The rule, as the paper formulates it

trees in view

"Every resident … should be able to see at least three trees from their home, school, or place of work." Preferably well-established trees.

30%

canopy cover

At least 30% tree canopy cover in every neighbourhood, not on average across the city. In dry climates 30% vegetation, with a strong tree component.

300 m

to a park

A large public green space within 300 m of every home, "approximately a 5-min walk". The WHO mentions an area of at least 1 hectare.

What is each part based on?

3: seeing green

A view of trees and other green from home, work or school is associated with better mental health and better performance. The paper calls the three trees a proxy, a handy measure of visible green: trees are valued in all cultures and are easy to see. As an example of policy it mentions Frederiksberg (Denmark), which wants at least one tree visible from every home.

30: living among the green

More tree canopy in the immediate surroundings goes with cooling and better health; Astell-Burt and Feng found better sleep and mental health with higher canopy cover, with clear benefits from 30%. Noticeable cooling may need more: Ziter et al. (2019) only found substantial cooling from about 40%. The paper therefore calls 30% a minimum. The target applies per neighbourhood, because a city average can hide inequality between neighbourhoods.

300: using the green

Green close to home is used more often, with positive effects on mental, physical and social health. Based on a literature review (WHO, 2017), WHO Europe recommends a public green space of at least 1 ha within 300 m of every home. The paper also mentions other norms, such as 2 ha within 300 m in England and 500 m to a 2 ha wood (Woodland Trust).

The paper's own caveats

It is a guideline, not a law: "always must be used carefully and with sensitivity to the local context".
In dense existing neighbourhoods 30% with trees alone is sometimes not achievable; even then it helps to measure progress against it.
Trees have downsides too (pollen, volatile organic compounds); the choice of species matters.
Methods to measure and monitor the rule partly exist, but "further development and testing of methods will be needed". The paper presents measurability as an advantage: it lets you track progress and compare cities.

How this map relates to the paper

Part	Paper	This map	Consequence
3: where	from home, school and workplace	homes only	Schools and workplaces are not calculated (yet).
3: which trees	well-established trees	all trees in the NEO data, including "disappeared, small tree" (21%)	The score can be too favourable; see the 3.
3: seeing	not defined	clear line of sight within 30 m, at eye height outside the facade	Our own, verifiable interpretation; see the 3.
30: area	neighbourhood	CBS neighbourhood (also shown per district and municipality)	Matches the paper.
30: denominator	not defined	land area (without water)	Neighbourhoods with much water are not disadvantaged; see the 30.
300: distance	300 m, about a 5-minute walk	a 5-minute walk over the network of streets and paths	Matches the paper; see the 300.
300: which green	large public green space; WHO: ≥ 1 ha	park or wood of ≥ 300 m²	Much more green counts than the WHO means, so the result is more favourable. An important improvement to make.