Lancaster study shows trees are the cities' cleaners

A league table of tree species with the capability to cut pollution in Britain's cities has come out of a three year study by Lancaster researchers on the effects of urban trees on urban air quality.

Professor Nick Hewitt from the University's department of Environmental Science and Professor David Fowler from the Centre for Ecology and Hydrology in Edinburgh led the research team who carried out tests in the Birmingham area. The research shows that trees are three times more effective at capturing particles from urban air than grassland.

The three-year research projects looking at the effects of trees on urban air quality. The study was funded by the Natural Environment Research Council as part of their Urban Regeneration and the Environment (URGENT) programme.

Professor Hewitt said: "Trees are an integral part of our urban landscape and we want to understand how they help air quality. Trees are effective at capturing particles, which are damaging to health, but with some species this has to be balanced against their emissions of gases which have the potential to form pollution. Computer modelling shows that only mass planting of oaks, willows and poplars would have a negative effect on air quality. Planting most tree species would improve air quality."

Professor Fowler said: "Urban trees can be used to reduce concentrations of particles in urban air and to reduce the effects of urban areas on the surrounding region. It is predicted that large-scale tree planting in the West Midlands conurbation could cut the concentration of harmful particles by 10 to 25 per cent and reduce the number of deaths that occur each year as a result of air pollution by as much as 140."

The findings will be presented at a conference held at Birmingham University to be held on Tuesday, May 28, chaired by Nerys Jones, chief executive of the National Urban Forestry Unit.