Trees breath life into gardens – and city streets

As the tree planting season gets begins in earnest new research shows that urban foliage can help reduce asthma attacks

This column has long sung the praises of trees both for their aesthetic appeal and as a home for wildlife

ONE of the more interesting elements of the now derailed Belfast-Derry joint bid for European City of Culture was the proposal for an urban forest in Belfast city centre stretching along Royal Avenue towards the expanded Ulster University at York Street.

There's little detail about the project or how its sponsors suggested clearing the footpaths daily of autumn foliage – always a concern when pedestrians, woodland and hard surfaces meet but not necessarily a reason to ditch the idea altogether.

This column has long sung the praises of trees both for their aesthetic appeal and as a home for wildlife. Now they have an additional selling point, if one were needed.

A scientific study carried out by the University of Exeter's medical school has found people living in polluted urban areas are far less likely to be admitted to hospital with asthma when there are lots of trees in their neighbourhood.

The study into the impact of urban greenery on asthma suggests that respiratory health can be improved by the expansion of tree cover in very polluted urban areas.

The study, published in the journal Environment International, looked at more than 650,000 serious asthma attacks over a 15 year period. Emergency hospitalisations were compared across 26,000 urban areas in England.

In the most polluted urban areas, trees had a particularly strong association with fewer emergency asthma cases. In relatively unpolluted urban neighbourhoods trees did not have the same impact.

The findings could have important implications for planning and public health policy, and suggest that tree planting could play a role in reducing the effects of air pollution from cars. They may also help the case for an urban forest stretching down Belfast's Royal Avenue towards the expanded Ulster University.

More than 5.4 million people receive treatment for asthma in Britain and the north with an annual cost to the NHS of around £1 billion. It's estimated that asthma causes over a thousand deaths a year.

The study was led by Dr Ian Alcock, research fellow at the University of Exeter's Medical School, who wanted to establish a correlation between urban vegetation and respiratory health.

“We know that trees remove the air pollutants which can bring on asthma attacks, but in some situations they can also cause localised build-ups of particulates by preventing their dispersion by wind – and vegetation can also produce allergenic pollen which exacerbates asthma,” he said.

“We found that on balance, urban vegetation appears to do significantly more good than harm.”

Even if you live in area of little pollution and/or are sceptical about the research's claims, I'd still urge you plant trees, because they look great and provide a great habitat for wildlife.

Over winter is the time to plant bare root trees, which are cheaper than those sold in pots. One drawback with bare root is that the selection is usually limited to native or naturalised trees, or hedging – though that's still plenty to choose from.

Another drawback, though one that is easily overcome, is that the roots of the young saplings must be kept covered so as they don't dry out. They'll most likely be sold to you in a bin liner, though this will only protect it in the very short-term. Ideally, have a trench dug where you can ‘heal-in' the young trees then plant them at your leisure any time between now and March.

Be warned that, if you're thinking about buying bare root trees, do it sooner rather than later, as there's finite stock and thankfully tree-planting is proving increasingly popular.

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