For anyone who may be new to urban forestry, what is the 3-30-300 principle, and why has it become such a powerful framework for creating greener, healthier, and more resilient cities?

"The 3-30-300 principle proposes a set of measurable minimum targets for green and healthy communities. Launched in early 2021, it's derived from the latest research on the importance of visible and nearby trees and green spaces for, among other things, public health and climate adaptation.

The principle calls for at least 3 mature trees visible from every home, workplace, school, or place of care. It also sets a requirement of at least 30% tree canopy cover in every neighbourhood. Finally, in line with a recommendation from the World Health Organization, the principle stipulates that we should all have an accessible, safe, and high-quality green space within a 300-metre walk from our home.

I think the popularity and wide application of this principle can be explained by its simplicity, while still being rooted in evidence. It is measurable and actionable — everyone can work with it."

Why do you believe that access to urban trees and green space should be considered a matter of equity for public health and wellbeing, and not simply an environmental matter?

"A rapidly expanding body of research shows how important nearby trees and green space are to our mental, physical, and social health and wellbeing. Trees moderate the effects of heatwaves, for example. Green spaces and leafy urban areas entice us to go outside more and be active. They also encourage social interactions. Just looking at trees and other nature stimulates our creativity and learning, and can reduce stress."

The 3-30-300 principle has gained international recognition. Looking around the world, what have you learned from cities that are successfully translating these ambitions into action?

"Some cities have now been applying the principle for several years, and we're beginning to see the results. Malmö, Sweden, for example, has included it in its city masterplan, meaning all city departments work towards its goals. New neighbourhoods are being created that are '3-30-300-proof', and canopy cover has increased substantially in some of the city's most tree-deprived areas. Similarly, in Arnhem in the Netherlands, the principle has driven new greening efforts in particularly vulnerable and heavily built-up neighbourhoods."

Having seen our multi-partner Tree Equity for Hartlepool project in action and visited several of the areas benefiting from new tree planting, how do you think the initiative is helping to bring the 3-30-300 principle to life?

"It's been great to see how the principle has been used to really examine the town's provision of canopy and green spaces, identifying areas where, for example, new trees should be planted. Hartlepool has one of the lowest canopy covers in the UK, and like other towns and cities, it faces problems with heat, public health, and the like. The principle sets a long-term goal and encourages targeted action to make the town greener for all residents."

With climate pressures intensifying, how important is it that cities take an evidence-led approach to tree planting, focusing not only on where they're planted, but on selecting the right species?

"This is essential. Space and resources are limited when it comes to planting new trees, so we need to identify priority areas where the need is greatest. We also have to ensure trees are given the best possible start by considering above- and below-ground space requirements, choosing the right tree for the right place, and following proper establishment practices. Only then will trees have the chance to thrive and grow to maturity."

What would you say are the biggest barriers currently preventing towns and cities from achieving meaningful tree equity and reaching ambitions such as 30% tree canopy cover?

"Space and resources are definitely challenges. In dense, historic urban areas, it can be difficult to find suitable locations for new trees. But honestly, it often comes down to political priorities. A great deal can be achieved when trees are recognised as essential to climate resilience, public health, and the economic development of towns and cities."

Hartlepool currently has one of the lowest levels of urban tree canopy cover in the UK. Through the Tree Equity for Hartlepool project, Trees for Cities and partners are using data and community engagement to identify where trees are needed most, and to ensure investment reaches the neighbourhoods that will benefit most. Cecil Konijnendijk's framework underpins this work, and it was a pleasure to welcome him to a number of our current and future Hartlepool planting sites, including a local primary school.

Community engagement sits at the heart of many successful urban forestry programmes. How important are community stewardship and local ownership in ensuring tree planting projects create lasting change?

"Very important! I always say that tree planting is great, but tree protection and stewardship are even more important. We need to build strong connections between people and trees, fostering a culture of care. Without community support and stewardship, many trees simply won't survive or thrive in the long term."

Looking ahead to 2030, what would success for urban trees and tree equity look like, both in the UK and around the world? What changes would you hope to see in the way towns and cities invest in and value their urban forests?

"I think we've taken some important steps towards creating greener, healthier, and more vibrant communities where trees and tree equity are properly valued. But much remains to be done, and many neighbourhoods in the UK and elsewhere continue to lose canopy cover and access to green space. I hope that by 2030, trees and tree equity will be an integral part of city policies, strategies, and development plans."

Grounded in his evidence-based, replicable, and measurable framework, Cecil's vision for the future is already taking root, bringing us closer to greener, healthier, and more climate-resilient towns and cities for everyone. Initiatives like our multi-partner Tree Equity for Hartlepool project are already showing what that future might look like.