Urban trees and green spaces in our cities have the potential to mitigate the impact of air pollution, allergy symptoms, heat, and stress. So how do we get better access to them?

In our cities and urban spaces, trees and vegetation act as natural filters, trapping airborne pollutants such as pollen, dust, and particulate matter. They reduce the concentration of allergens in the air, alleviating allergy symptoms for those struggling with respiratory conditions.

Although many trees and plants produce allergenic pollen, the presence of a diverse range of plant species in urban green spaces — even along streets and city centres — can dilute the concentration of allergens and reduce the pollen load. Which is why a strategic selection of non-allergenic or low-allergenic plant species in urban landscaping is key to helping minimise pollen-related allergies, like hayfever.

From about March until May, the blossoming of trees such as hazel and birch creates the first wave of symptoms for some pollen allergy sufferers.

What’s more, enhancing biodiversity in cities can contribute to ecosystem resilience, strengthening natural pest control mechanisms, thereby reducing the need for chemical pesticides that may exacerbate allergies.

How does heat exacerbate allergies?

Hot and dry weather conditions can facilitate the dispersion of airborne allergens such as pollen, mold spores, and dust particles, and exacerbate levels of ozone and particulate matter. Heat-induced stress responses in the body are also known to amplify allergic reactions and symptoms, which is why finding ways to keep our cities cool is so important, as we head into the future.

A new study from the Global Centre for Clean Air Research (GCARE) has provided insight into the heat-mitigating effects of green spaces during heatwaves, finding that botanical gardens are one of the most effective ways of cooling cities — followed by wetlands, urban parks, green walls, street trees and playgrounds.

Read more: Why are allergies on the rise?

The review’s findings can, it’s hoped, help inform policymakers with urban planning, as we continue to deal with rising temperatures of growing severity.

LEARN MORE: ITN Business announces Allergy Aware programme

“We have known for some time that green spaces and water can cool cities down,” said GCARE director, Professor Prashant Kumar, lead author of the study.

“By incorporating green-blue-grey [human-engineered infrastructure for water resources] infrastructure (GBGI) into urban planning, cities can create more sustainable and resilient environments, mitigating the adverse effects of heatwaves and improving overall live-ability for residents,” he said.

The diverse array of natural elements in botanical gardens, such as various vegetation, tree species, shrubs, and grass, in addition to water features like ponds, brooks, and waterfalls, creates a certain combination that results in a ‘unique cooling mechanism’.

The review also found that cities can unlock more benefits by linking green spaces together into ‘green corridors’.

The power of greenery in our cities for stress reduction

Access to green spaces has been linked to improved mental health and wellbeing, including reduced stress and anxiety levels. Lower stress levels can enhance the body’s immune response and resilience to allergens, potentially mitigating the severity of allergic reactions.

Urban trees and green spaces offer huge benefits for climate regulation and personal wellbeing, but as Simone Borelli, an urban forestry expert at the United Nations’ Food and Agriculture Organisation (FAO) has said, it’s our access to trees, not their quantity, that really matters, and whether city-dwellers can sense, see, or even touch the trees in their city.

Botanical gardens were found to be the best type of green space for cooling cities.

How can we improve our access to green spaces?

Efforts to improve the amount of green spaces in cities and people’s access to them are underway around the world, driven by various stakeholders, including governments, urban planners, community organizations, and environmental advocates.

Prof Prashant Kumar of GCARE is a director at the RECLAIM Network Plus, which brings together academics, city officials, charities and businesses with an interest in urban planning. Through the Network as well as GCARE, a growing number of initiatives are being launched to drive tree planting and improve green spaces and people’s access to them across the country.

The RECLAIM Network Plus conference takes place at the Barbican Centre in London on 23 May. The event brings together researchers, policymakers, and industry leaders to discuss and share best practice around green, blue and grey infrastructures. 

Other key initiatives and strategies include creating pocket parks and community gardens, retrofitting vacant lots and rooftops with green infrastructure, and reclaiming underutilised spaces for public parks and recreational areas.

Governments and local authorities are investing in the expansion and rehabilitation of existing parks and green spaces to enhance their accessibility, usability, and ecological value. This includes initiatives to restore degraded ecosystems, improve biodiversity, and create multi-functional green spaces that serve as habitats for wildlife, recreational areas for residents, and natural buffers against climate impacts.

Data shows the UK is one of the world’s most nature-depleted countries; in the bottom 10% globally and last among the G7 nations.

Green infrastructure development

Green infrastructure, such as green roofs, rain gardens, bioswales, and permeable pavements, is being incorporated into urban planning and development projects to manage stormwater, reduce urban heat island effects, improve air quality, and enhance biodiversity. Green infrastructure not only provides ecological benefits but also creates opportunities for recreational activities and community engagement.

There is a growing recognition of the importance of equitable access to green spaces, particularly in underserved and marginalised communities. Urban planning efforts are increasingly focused on addressing disparities in access to parks and green spaces, ensuring that all residents, regardless of income or ethnicity, have access to high-quality green spaces within walking distance of their homes.

Experts believe green space can also deliver additional benefits that may be particularly important in underserved neighbourhoods, through providing areas for community, connection and leisure, creating safer streets and reducing building energy costs associated with cooling.

Learn more in ITN Business’ Urban Evolution programme

Find out how your business could be featured in ‘Urban Evolution: Our Future Cities

Populations within cities are growing at an alarming rate, with urban growth driving environmental change, but inequalities remain. Infrastructure needs to be climate ready, looking at the adaptation of buildings already in existence and resilience in the built environment. This oncoming age of climate breakdown alongside rapid urbanisation, means urban transformation is essential if cities are to address these challenges ahead and meet global climate and development goals. ​

ITN Business will produce a news-style programme Urban Evolution: Our Future Cities to be launched at the Net Zero Festival, the 22–23 October, 2024. ​Presented by Broadcaster and Anthropologist Mary-Ann Ochota, in ITN’s London studio, the programme will focus on the organisations leading the way when it comes to:

  • Creating more resilient, affordable and accessible cities
  • The innovative solutions to cut carbon emissions
  • Initiatives to promote good mental, physical and social health

Urban Evolution: Our Future Cities will also feature insightful interviews from industry thought leaders Business Green, Smart Cities Council, UK100, UK Green Building Council and the World Green Building Council.

There are commercial opportunities for leading organisations to be featured in the programme and spearhead their own news item. If your organisation wants to share what you stand for and be part of this important conversation about the future of our cities, please contact our ITN Business Programming Directors, Jeff Blackmore or Tamsin Luck.

Watch our 2023 programme, Cities of the Future, and have a listen to our podcast on how cities need to decarbonise, adapt and prepare for the rapid urbanisation ahead — hosted by broadcaster and anthropologist Mary-Ann Ochota.