Trees are woven into our urban and rural fabric, and in highly populated areas precious space is given over to their retention, writes Jago Keen chairman of the Arboricultural Association.
Trees provide so many benefits to our way of life, from urban temperature regulation and noise reduction through to carbon storage and, in an increasingly polluted world, air purification.
So how do trees affect air quality, and should the scientific community be bringing more pressure to bear on landowners and legislators to recognise the role that trees have to play in helping to manage and cleanse our day-to-day living environment?
The air that we breathe
In the UK the NHS has appointed a Director of Forests; perhaps a tacit recognition that trees have a role to play in helping to prevent or cure disease, whether physical or mental.
The NHS claims to have planted hundreds of thousands of trees around NHS sites with the intention of providing both visual amenity – and as we shall see, trying to manage and control the incidence of disease.
UK National planning policy has also started to wake up to the role that tree’d environments can play. Development guidelines and process now have to pay some attention to the issue of air quality and link trees into sustainable development policies for green infrastructure provision.
By their very nature trees are the largest and most frequent component of green infrastructure and (if well maintained) deliver increasing health benefits over long periods of time.
On a wider global scale the World Health Organisation is clear that air pollution is a major environmental risk to health. Urban outdoor air pollution has been estimated to cause 1.3 million deaths per annum worldwide, mainly through respiratory infections, heart disease and lung cancer.
And we can get more specific. Research in the United States has clearly identified an additional 15,000 deaths due to respiratory tract disease and 6,000 deaths due to cardiovascular disease through the loss of one tree species.
In this case a pest, the emerald ash borer, has been identified as the culprit. First discovered in 2002 the borer attacks ash trees, killing nearly all of the trees it strikes; in the north western US states the borer caused the loss of over 100 million trees.
Researchers from the US Forest Service analysed mortality in these areas and found consistently repeated patterns of increased human mortality related to the regions of pest invasion.
Webiste: Arboricultural Association - Trees tackle air pollution
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