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Hug a tree, save your life

At the risk of looking like a green caricature, I’ll admit it. I sometimes hug trees.

As a city dweller I so value my local parks – big and small – and nearby nature reserves. They are little islands of peace and space and breathable air where I can walk and sit and think and recharge my body and mind.

So it was encouraging this week to see a new study from the USDA Forest Services and the Davey Institute in New York which put a slightly new spin on the value of trees in our lives.

In the developed – and increasingly in the developing – world air pollution is a real problem. It affects human health and well-being, ecosystem health, crops, climate and more.

The retrospective study looked at data from 2010. It estimated US tree cover – about 34% of the country – and then calculated how much pollution that tree cover removed from the atmosphere and what the value of that clean-up was in terms of its effect on respiratory problems like asthma.

The scientists focussed on four pollutants for which there are established air quality standards in the US: nitrogen dioxide (NO₂₎, ozone (O₃₎, sulphur dioxide, and particulate matter less than 2.5 microns (PM_2.5) in diameter.

Trees, it turns out are saving more than 850 human lives a year and preventing 670,000 incidents of acute respiratory symptoms. The number of lives saved may not seem high, but it is particularly significant in urban areas. For instance the savings on healthcare and other costs in urban areas accounted for 68% of the estimated $7 billion savings.

These are figures that should make any politician or regulator (or for that matter city planner) sit up and take notice.

The more trees there were the greater the benefit, particularly in urban areas. And of course the researchers only looked at benefits for respiratory problems like asthma. Pollution is also associated with higher rates of and heart disease and detrimental effects on the circulatory and neurological systems.

A 2013 assessment by World Health Organization’s International Agency for Research on Cancer (IARC) concluded that outdoor air pollution is carcinogenic to humans, and that the particulate matter component of air pollution most closely associated with increased cancer incidence, especially cancer of the lung but also cancer of the urinary tract/bladder.

But trees also affect air quality in ways not analysed in this paper. Trees also emit varying levels of volatile organic compounds (VOCs) that can help keep the planet cool. Planted around buildings they provide shade and so lower the energy used to cool offices and homes in the summertime – this can have knock on effect of lowering emissions from power plants.  Noise pollution from highways and other sources can also be reduced with trees. And of course, in the context of the last two seasons of floods in the UK, planting more trees is one of the most efficient ways of keeping floodwaters down.

Then there are the more intangible values. Trees provide important symbolic links with the past. We use the phrase “tree of life” to describe the interconnectedness of all life on our planet and as a way of reminding ourselves about our common evolutionary descent.

There are emotional and psychological benefits, too, of seeing, touching and smelling nature, and these values too have been shown to be higher in urban areas too where too many of us are nature starved. Studies have shown both mental health benefits and other studies have shown immune system benefits of simple activities like walking or exercising in the parks and woods.

Perhaps it’s time to realign our relationships with our trees. They are not just there to make toilet paper, furniture and flooring.

Where ever you are, plant more trees (and if you feel like it hug them too). It could just save your life.

Pat Thomas, Editor