Trees Alleviate Pollution in Cities, Study Finds

A new study conducted by scientists at the University of Leicester has concluded that trees could help to disperse pollution in cities across the country, thus purifying the air we breathe. The paper, published in the science journal Atmospheric Environment, was a collaboration between the university, Bluesky International Ltd and the Natural Environment Research Council (NERC).

By using the High Performance Computing services’ ALICE supercomputer to create a model of buildings and trees (collated from data provided by Leicester City Council and Bluesky National Tree Map (NTM)), the researchers were able to determine that trees reduced pedestrian-height pollution by up to 7%.

A Patch of Good Turbulence

Previous studies had suggested that a high density of trees in city centres was actually detrimental to air quality, since the foliage could trap pollution in street canyons due to reduced wind flow. However, although there were some instances where they were to found increase pollution, on the whole trees were found to be largely beneficial in dispersing pollution.

As well as reducing wind flow, trees also help to increase turbulence, which is key to widespread dispersal of harmful elements in the air. This means that human pedestrians and cyclists are less susceptible to exposure.

Meanwhile, trees also hold a number of other proven health benefits, such as the physical and chemical removal of specific contaminants from the area. Furthermore, they can be instrumental in reducing noise pollution and lowering stress levels among harried city dwellers.

Expanding the Analysis

This particular study focused on Leicester city centre, where as much as 90% of all NO2 emissions are caused by vehicular traffic. However, the findings could be extrapolated to other cities and offer insight into the beneficial effects of trees on a national and perhaps even international scale.

“Basing this type of study on the most up to date and accurate geographic data, such as the National Tree Map, allows for the results to be validated and the studies replicated for other locations and types of environment further enhancing our understanding of air pollution and the important role played by trees,” explained James Eddy, the technical director of Bluesky and the company’s industrial associate at the University of Leicester.

Trees have long been known to have a beneficial effect on our environment. As absorbers of carbon dioxide and emitters of oxygen, widespread forestation of desert areas has been touted as one curative measure of the harmful effects of global warming and climate change. Now, it appears that planting more trees could have not just a long-term global effect on the state of the air we breathe, but that its effects could be seen more immediately in an urban scenario, too.