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Cities often struggle to make space for nature to thrive. However, the future of resilient, liveable cities depends on the health and growth of their urban forests, says Heidi Kagiali of PEFC International.
Amid heatwaves globally, many have felt the effects of tree-poor cities with urban residents suffering in heat islands deprived of the significant cooling effect that trees provide. The trees that do exist in urban areas are also facing challenges from rising temperatures. For example, this summer, a London council warned that there has been an increase in ‘sudden branch drop’, which has been made worse by the heatwaves. Such incidents highlight the pressures trees face in urban environments, and the importance of active management and planning.
With thoughtful planning, the city can be a place where trees and green spaces can thrive. And this planning is well worth undertaking due to the environmental, economic and social benefits to greening our cities. Incentives to champion urban forestry are already being put into place – such as PEFC’s Trees Outside Forests Certification, and are proof of what is possible. These successes can provide a framework for other cities to learn from, too.
The challenges of urban forestry
With competing priorities such as crime, homelessness, and fulfilling daily needs of residents, projects such as urban forestry are often less of a priority for decision makers. Whilst there may be a lack of urgency at governance level, residents certainly feel the impact – 79 per cent of UK city residents say that having access to nature and green space is a priority for them.
Although there are plenty of trees already growing in cities, challenges remain. Mature city trees that were planted decades ago in a different local climate could be struggling to thrive in present climates without proper care. Development often encroaches on their root systems, and their surrounding soil degrading over time can make it challenging to get nutrients and water.
Taller buildings also cast greater shadows, placing trees which once enjoyed sunshine into darker environments, hindering their photosynthetic cycle. Lastly, biodiversity such as birds, squirrels, and insects that have a symbiotic relationship with the trees are less likely to remain in the area if pollination, food, and soil aeriation are less prevalent. A city is not an easy place for a tree to grow without appropriate intervention.
The significance of urban forests
An issue of growing concern is heat, especially this summer where heatwaves and drought warnings have been prevalent. Concrete surfaces under tree-created shade can be up to 20 °C cooler than ones in direct sunshine. Trees can also have a cooling effect of between 2-5°C, depending on their size.
Moreover, 1,000 people a year are hospitalised due to air pollution each year in London alone. Trees have a significant impact on airborne pollution with London’s urban forests removing around 2,200 tonnes of particulate matter from the air yearly. Finally, introducing compatible species of trees to the city can also boost biodiversity. Two thirds of all bird species rely on forests to survive and thousands of species globally rely on trees in some way. Well planned urban green spaces also create corridors for biodiversity to migrate and thrive.
Economic impacts of urban trees
Trees also have a significant positive economic impact on cities and the people that live there. Being around trees and nature has been shown to improve mood, reduce stress, and sharpen focus. Trees and green spaces also have a positive impact on house prices: homes near a park are, on average, between two and eight per cent more expensive whilst properties in neighbourhoods with abundant mature trees can be worth hundreds of thousands more than in those without.
The running costs of a home are also reduced by trees and the shade they provide – shading an air conditioning unit can increase its efficiency by 10 percent.. Trees can also act as windbreaks, reducing heating costs in the winter.
How trees can be a bigger part of city planning
To reap the benefits of urban forests, they must be embedded at the city planning. Urban forestry must not be an afterthought but rather it should have its own dedicated policies, funding, and experts at hand for accountability. This can be done by implementing green infrastructure legislation which requires a certain number of trees to be planted in new developments, or in cases where existing spaces are being re-designed – this has been successfully implemented in Canberra where two trees must be planted for every one removed.
Cataloguing and protecting existing trees can also ensure they are valued as city assets, while dedicated funding and professional management teams help secure their long-term care.
Urban forests in The Netherlands
The Netherlands has pioneered urban forestry and is home to Zwolle, the first city to receive PEFC’s ‘Trees Outside Forests’ (TOF) certification – a global recognition of its sustainable management practices. This is of particular importance as half of The Netherland’s trees grow outside of traditional forest settings.
Working with local forestry organisations, PEFC supported a stakeholder-driven process involving ecologists, municipalities, and planners to adapt benchmark standards to Dutch needs. Certification now recognises these cities for their sustainable management of trees outside forests, setting an example for others worldwide.
Looking ahead
Urban forestry brings clear environmental, social, and economic advantages. Despite this, many cities are lagging behind, held back by funding challenges, legislative barriers, and competing priorities. With careful planning, appropriate funding, and the right partnerships, cities can ensure that trees and green spaces thrive alongside concrete and steel. PEFC’s TOF certification shows that sustainable management is possible, and that greener, healthier, and more resilient cities are within reach.
Heidi Kagiali is a forestry professional currently serving as Forestry & Conservation Manager at PEFC International, where she leads projects on the sustainable management of forests and trees outside forests.
