Trees and their role in filtering out pollution
Trees in London can give air quality a boost by filtering out pollution particulates, new British research shows. Presented in the November issue of the journal Landscape and Urban Planning, the study is an outcome of the BRIDGE ('Sustainable urban planning decision support accounting for urban metabolism') project, which has clinched EUR 3.1 million under the Environment Theme of the EU's Seventh Framework Programme (FP7). The methodology developed in this study enables scientists to predict the amount of pollution that can be removed in the future, as we face changes in the climate and increased pollution emissions.
Pollution particulates affect the health of humans. Researchers at the University of Southampton in the United Kingdom say urban trees of the Greater London Authority (GLA) area can remove anywhere between 850 and 2 000 tonnes of particulate pollution (PM10) from the air each year. Adding more trees on the streets of London, as well as across England, in the coming years is a step in the right direction. Such a move would help meet the targets the GLA has set: to plant more trees between now and 2050. The plan would also support 'Big Tree Plant', an initiative of the David Cameron government of the United Kingdom.
The data suggest that the future air quality in terms of PM10 removal would get a huge boost if trees are planted in the most polluted areas of the GLA area. It should be noted that using a variety of trees including evergreens like pines and evergreen oak would be an even better choice to make this objective fruitful.
'Trees have evolved to remove carbon dioxide (CO2) from the atmosphere, so it's not surprising that they are also good at removing pollutants,' says one of the authors of the study Professor Gail Taylor of the University of Southampton. 'Trees which have leaves the whole year are exposed to more pollution and so they take up more. Using a number of different tree species and modelling approaches, the effectiveness of the tree canopy for clean air can be optimised.'
In this study, the researchers offer predictions of PM10 uptake in future climate scenarios and for five tree planting scenarios in London. The use of seasonal and not hourly data, according to the team, had little effect on modelled annual deposition of pollution to urban canopies. This, they say, makes one consider that pollution uptake can be estimated in other cities as well as for the future where hourly data are not available.
'We know that particulates can damage human health, for example exacerbating asthma and this reduction in exposure could have real benefits in some places, such as around the edge of school playgrounds,' says co-author Peter Freer-Smith, chief scientist for Forest Research (Forest Commission) and Visiting Professor at the University of Southampton. 'Urban greenspace and trees give a wide range of benefits and this study confirms that improving air quality is one of them and will also help us to get the most out of this benefit in future.'
The BRIDGE project is coordinated by the Foundation For Research and Technology-HELLAS, Crete in Greece and the consortium includes partners from France, Germany,, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Switzerland and the United Kingdom. The project has been funded by DG Research and Innovation, Enviroment Programme, Management of Natural Resources.