A new study published in the Environmental Science and Technology Journal has found that increasing the number of green walls in cities could help reduce levels of pollution.
Currently, the groups of high rise buildings create what experts call ‘street canyons’. These prevent pollution from escaping naturally into the atmosphere, instead collecting in pockets in the city where it can become harmful to human health. The study has found however, that by making streets greener, the levels of pollution could be reduced.
Although planting trees can create a more green urban environment, councils have been criticised for planting too many small trees. Instead, specialists recommend the planting of larger trees in smaller numbers. A more cohesive urban planting strategy is being called for, which helps reduce flooding, increase biodiversity and cut pollution.
Pollution cuts have been proven to be achievable through greening areas in urban settings, but levels of reduction have only been seen to be around 5%. Implementation of a targeted strategy which ensures planting is installed in areas where the largest impact can be had has been projected using computer modelling to have the capacity to reduce pollution by up to 30%. Green walls are the future according to Professor Rob MacKenzie, co-author of the study.
The key, according to Rob, is to adopt the approach of cleaning the air that stays in and enters the street canyons, rather than continuing to adopt top down solutions that have tended to be the approach taken over the past few years, such as installing catalytic converters in vehicles. Although these methods may have reduced the amount of pollution from each car, they haven’t succeeded in reducing the particulate matter and nitrogen dioxide that can accumulate sufficiently.
Transport for London’s Nicola Cheetham also commented on the findings, saying they were in alignment with findings in research being conducting at Imperial College London. The second green wall in the city has just been constructed to help reduce pollutant levels where high volumes of traffic use the urban area.