HQ Team
December 8, 2022: Concrete and brick structures are taking over swathes of land. Almost 70 per cent of the world’s population resides in urban centres. According to the UN, we have become a majority-urban species. By 2050, projections suggest almost 70 per cent of us will be urban dwellers.
The Pandemic, which put us on a prolonged lockdown, brought to the fore the need for greener breathing spaces to break the tedium. It is known that green and verdant areas promote mental peace and health.
A new study led by ISGlobal, Foundation, the Barcelona Institute for Global Health, studied the relationship between better mental health and the 3-30-300 green space rule. According to this rule of thumb, everyone should be able to see at least three trees from their home, have 30% tree canopy cover in their neighbourhood and not live more than 300 metres away from the nearest park or green space.
This rule was propagated by urban forester Cecil Konijnendijk and is widely followed by urban planners across the world.
“There is an urgent need to provide citizens with more green space,” lead study author and ISGlobal Director of the Urban Planning, Environment and Health Initiative Mark Nieuwenhuijsen said in a statement. “We may need to tear out asphalt and plant more trees, which would not only improve health but also reduce heat island effects and contribute to carbon capture.”
The ISGlobal study was based on a sample of 3,145 Barcelona inhabitants aged 15-97 years who participated in the Barcelona Health Survey 2016 -made by The Barcelona Public Health Agency- and were recruited randomly. Mental health status was assessed based on a questionnaire. Over 18% of participants reported poor mental health and 8.3% reported having visited a psychologist in the previous year, 9.4% reported using tranquillisers or sedatives and 8.1% reported having used antidepressants in the previous two days.
The ISGlobal study revealed that urban areas that followed the 3-30-300 rule had residents with better mental health, and reported lesser dependence on medications and psychologists. The association was statistically significant only for the latter.
“The study found that there is relatively little green space in Barcelona and that the 3-30-300 rule is satisfied only for a small percentage of people, despite its beneficial mental health effects,” explained Mark Nieuwenhuijsen. “Any initiative that leads to a greener city will be a step forward, the key message is that we need more and faster greening”, he added.
Overall, almost a quarter of Barcelona residents lived somewhere that met none of the rule’s criteria.
According to the research team, similar studies should be carried out in cities with more tree cover than Barcelona for a better perspective on the 30% criterion.. “The question is to what extent 30% tree canopy cover is feasible, especially in compact cities,” the researchers concluded.
A 2019 study found that people who spent at least two hours in nature a week reported better physical and mental health. In cities, greenery can reduce the heat effect and boost cognitive function, among other benefits.
