With housing a priority for Britain's new government, researchers at the University of Surrey are urging city planners not to forget about building “green spaces” such as parks in new communities.
Surrey's Global Center for Clean Air Research (GCARE), working with 30 co-authors from seven countries, has found that parks may be the most effective solution to reducing overall air pollution – reducing air pollution citywide by 22%. However, the study highlights the importance of assessing how well different types of green, blue and gray infrastructure (GBGI) work in smaller areas and recognizing that parks can include multiple features that combine to increase their impact.
The study also examined other common types of green, blue and gray infrastructure (GBGI), such as trees, green walls and hedges, and found mixed results regarding their ability to reduce air pollution.
Trees were most effective on open roads, where they could reduce pollution by up to 77%. However, researchers found that planting trees in narrow, closed streets – called urban canyons – can sometimes worsen air quality. This is because certain tree species and arrangements can block airflow, trapping pollutants.
Professor Prashant Kumar, lead author of the study and founding director of GCARE at the University of Surrey and director of RECLAIM, said:
“We are beginning to understand how effective green infrastructure can be against urban air pollution, but its effectiveness depends on where and how it is implemented. Our research shows that well-placed green spaces can reduce black carbon levels by up to 40%. “We are making our communities greener and healthier.”
The research is part of the RECLAIM project (Reclaiming Forgotten Cities – Turning Cities from Vulnerable Spaces to Healthy Places for People). RECLAIM is a £1.45 million UK-funded Network Plus research and innovation initiative. It is led by GCARE in collaboration with the UK Center for Ecology & Hydrology and the Universities of Bath, Bangor and Warwick.
According to the World Health Organization, outdoor air pollution caused 4.2 million deaths in 2019. The main sources of outdoor air pollution include vehicles, electricity generation, and residential energy for cooking and heating.
Professor Kumar added:
“We have found that many GBGIs lack scientific evidence to support their effectiveness in eliminating air pollution. Decisions are often based on expert judgment and therefore it is crucial that we close this knowledge gap as quickly as possible to enable informed decision making to maximize the potential of GBGI.”