The Landscape Institute has submitted evidence to a National Institute for Health and Care Excellence consultation ‘Air pollution: outdoor air quality and health’ to make the case for the role of urban trees in supporting healthy urban communities.
Professor Alan Simson, Professor of Landscape Architecture and Urban Forestry at Leeds Beckett University School of Art, Architecture and Design and a member of the LI’s technical committee said: “The NICE consultation does not acknowledge the role street tree plays in creating healthy communities as positively as it could and more research needs to be carried out into barriers and how street trees influence urban air quality. There is however more research available than acknowledged by the consultation.”
Vegetation is the most effective way of intercepting particulate aerial pollution. Trees, because of their large canopy surface area of leaves, stem and branches, and the air turbulence created by their structure, are the most effective form of vegetation for doing this.
The Landscape Institute would strongly maintain that planting trees of the right species, in the right place, in the right way and for the right reasons can greatly assist in helping to mitigate the effects of both particulate and gaseous pollution in urban areas. We know which tree species attract the most particulate pollution and how leaf size can influence this. We also know which tree species to avoid due to their excessive pollen production and there are proven benefits that single lines of street trees can bring to mitigating air pollution in certain situations.
There can be disadvantages from retaining or incorporating trees into urban areas. On occasion they may not have as positive an effect to mitigate air pollution. This can occur where tree canopies meet over roadways but this is rare in the UK. Trees can also emit biogenic volatile organic compounds [bVOCs] as a reaction to stress in their environment.
Professor Alan Simson, continued: “Urban forestry has moved from being seen as a ‘green cosmetic’ to becoming an integral part of a new, more resilient form of European urbanism. Design of the urban forest is becoming more sophisticated as the canopy area, structure and choice of tree species are critical in intercepting the maximum amount of pollution.
“It is the landscape architect’s mission to shape a better world. Landscape architecture and urban forestry have a role to play in the emerging, world-wide movement of New Urbanism. This is based on the belief that the true wealth of our towns and cities can only really be measured in terms of the well-being of our people and the sustainability of our environment.”