Green spaces improve schoolchildren's mental development, study finds

Research on primary school children in Barcelona suggests boost in short-term memory from nearby vegetation, due in part to reduction in traffic pollution

Children playing football at Placa de Sant Filip, Barcelona, Spain Photograph: Alamy

Green spaces within and around city schools improve the mental development of young children, a study has found. The findings may partly be explained by reduced exposure to traffic pollution, experts believe. Other influences could include the psychological effect of having views of fields and trees rather than roads and buildings.

The Spanish researchers found that each degree of increase in surrounding greenness led to a 5% improvement in the development of short-term, or working, memory over a period of one year. It also improved the progress of “superior working memory” – the ability to update memories with changing information – by 6%, and reduced inattentiveness. Computer analysis suggested that carbon from traffic fumes might account for up to 65% of the trend.

The researchers carried out mental performance tests on 2,593 children aged seven to 10 attending 36 primary schools in Barcelona every three months for a year. At this age, children’s brains are rapidly developing and their mental abilities improving. Over the study period, participants’ overall working memory increased by an average of 22.8%, and superior working memory by 15.2%, while inattentiveness decreased by 18.9%.

Exposure to green spaces was assessed with the help of satellite images. The scientists applied a measurement called Normalised Difference Vegetation Index (NDVI) based on the reflective properties of land surfaces. The results are reported in the journal Proceedings of the National Academy of Sciences.

Led by Dr Payam Dadvand, from the Centre for Research and Environmental Epidemiology in Barcelona, the researchers wrote: “Approximately one half of the world population lives in cities, and it is projected that by 2030, three of every five persons will live in urban areas worldwide.

“Urban areas are characterised by a network of non-natural built-up infrastructures with increased pollutant levels and less green environments. Children’s exposure to these pollutants such as air pollution and noise has been associated with detrimental impacts on their cognitive development.

“Our findings suggest a beneficial impact of green space exposure on cognitive development, with part of this effect resulting from buffering against such urban environmental pollutants.”

Schools that increased greenness within their boundaries by the amounts observed in the study could reduce the proportion of children with impaired superior working memory development by nearly 9%, said the researchers.

British experts said the study was interesting, but pointed out some limitations. Professor Andy Jones, from Norwich medical school at the University of East Anglia, said: “The measure of green space used was the amount of vegetation in the neighbourhoods of the children and their schools derived from satellite images. It was not a direct measure of usable green spaces, like public parks, although they will be included.

“The researchers know the amount of vegetation in the vicinity of the children, but not if the children actually came into contact with it. The only thing the researchers considered about the family was the level of education the mother had obtained. It might be that unmeasured family characteristics could at least partially explain the associations they observed.”

Dr Ross Cameron, senior lecturer in landscape management, ecology and design at the University of Sheffield, said: “The authors suggest a causal link between air quality and green space: poor air quality reducing attentiveness and cognitive function, green space tending to improve local air quality. They admit however that this factor only seems to explain part of their correlations.

“Socioeconomic factors are catered for, but there may be more subtle additional effects missing from the analyses and the authors acknowledge mental health of parents was not considered. For example, poorer areas tend to be less green, but also have higher incidences of health problems. Such impacts on parents may also affect their children in terms of educational performance.”