Trees along Dublin’s thoroughfares face a death sentence. In streets choked with vehicles, it’s proposed to cut them down so that buses can operate more efficiently.
Either cars or trees, it seems, must go. The tyranny of the motor car, alas, tends to triumph in such disputes.
However, losing the trees may have hidden consequences. A paper on the impact of the natural environment on people’s health has just appeared in Scientific Reports.
Its conclusions are timely given the Dublin row.
The paper examines the possible health effects of ‘exposure to’, or ‘contact with’ nature.
Members of the public were asked about the role the natural environment played in their everyday lives, its influence on their health and sense of wellbeing.
Men and women, young and old, of differing classes and ethnic backgrounds, participated in the survey.
There were both urban and rural dwellers, rich and poor, and people with chronic illnesses and disabilities.
‘Nature’, in this context, was interpreted loosely. It included not only wilderness areas such as woods wetlands and beaches, but also city parks and urban green spaces.
Tree-lined streets are not specifically mentioned in the paper but they would seem to qualify for inclusion.
Respondents had to estimate how long they spend in such natural settings each week, the durations of short visits being added to those of more prolonged ones to give an overall picture.
Almost 20,000 responses were documented. Dr Mat White, and a team at Exeter University, examined the findings.
Using the data, he constructed a representative model of the British population.
Analysing the results of self-reporting projects can be a statistical nightmare.
This one would seem to have presented particular challenges; participants did not face a level playing field.
Those in good health, for example, might be more inclined to venture out to parks and woodlands than people less well.
Those living in the centres of cities, or in built-up housing estates tend to have limited access to natural environments, while well-healed dwellers of leafy suburbs often have such locations on their doorsteps.
Using statistical pyrotechnics, however, the researches were able to control for such biases and come up with what they claim are robust conclusions.
Rather surprisingly, people who spent less than two hours per week in natural settings reported health outcomes which were no better than those of participants with no contact with nature at all.
Benefits and a sense of wellbeing only ‘kicked in’ with at least two hours’ exposure.
Once the two-hours-a-week threshold had been exceeded, however, increasingly positive results were reported.
Improvements continued until natural exposure reached five hours per week. Beyond that limit, little extra benefits were enjoyed.
The findings applied equally to men and women, rich and poor, urban and rural dwellers.
Nor were there significant differences between age groups or occupations.
Residing in affluent areas, the authors note, “is associated with lower probabilities of cardiovascular disease, obesity, diabetes, asthma, hospitalisation, mental distress, and ultimately mortality”.
Since more and more people worldwide live in cities, these results are important; town planners and Dublin transport engineers please note.
The authors hope to develop “nature exposure guidelines comparable to those for physical activity”.