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July 29, 2019

Increasing tree cover may be like a ‘superfood’ for community mental health

As the density of Australian cities continues to increase, investment in urban greening is more important than ever - but does the type of green space make a difference to our mental health?

 and increasing the proportion of homes in urban areas within 10 minutes鈥� walk of  are among the New South Wales premier鈥檚 new priorities. Cities around Australia have similar goals. In , we asked if more of any green space will do? Or does the type of green space matter for our mental health?

Our  suggest the type of green space does matter. Adults with 30% or more of their neighbourhood covered in some form of tree canopy had 31% lower odds of developing psychological distress. The same amount of tree cover was linked to 33% lower odds of developing fair to poor general health.

We also found poorer mental and general health among adults in areas with higher percentages of bare grass nearby, but there鈥檚 likely more to that than meets the eye.

How did we do the research?

Our research involved tracking changes in health over an average of about six years, for around 46,000 adults aged 45 years or older, living in Sydney, Newcastle or Wollongong. We examined health in relation to different types of green space available within a 1.6 kilometre (1 mile) walk from home.

Our method helped to guard against competing explanations for our results, such as differences in income, education, relationship status, sex, and age. We also restricted the sample to adults who did not move home, because it is plausible that people who are already healthier (for instance because they are more physically active) move into areas with more green space.

So is the answer simply more trees and less grass? Not exactly. Let鈥檚 get into the weeds.

Trees make it cool to walk

Imagine you鈥檙e walking down a typical street on a summer鈥檚 day in the middle of an Australian city. It鈥檚 full of right angles, grey or dark hard surfaces, glass structures, and innumerable advertisements competing for your attention. Then you turn a corner and your gaze is drawn upwards to a majestic tree canopy exploding with a vivid array of greens for as far as you can see.

Let鈥檚 get the obvious out of the way. Walking down this green street, you may instantly feel some relief from the summer heat.

Studies are linking high temperatures with heat exhaustion and . Research has suggested trees, rather than other forms of green space, may be . It may also simply be more comfortable to walk outside in cooler temperatures 鈥� not to mention going for a run or bike ride, both of which are .

Feeling restored and alert

But as the minutes of walking beneath this natural umbrella of lush foliage accumulate, other things are happening too. The vibrant colours, natural shapes and textures, fresh aromas, and rustling of leaves in the breeze all provide you with effortless distraction and relief from whatever it was you might have been thinking about, or even stressing over.

Studies back this up. Walks through green space have been shown to , . The Japanese have a name for this type of experience: .

Friends, old and new

You walk past groups of people on the footpath taking time to catch up over coffee in the shade. Some research has found that tree cover, rather than green space more generally, is a predictor of . Social capital, , refers to the 鈥渟ocial networks and the associated norms of reciprocity and trustworthiness鈥� that may have important influences on our life chances and .

You walk further and a chorus of birdsong soars through the neighbourhood noise. Trees provide shelter and food for a variety of animals. Research suggests tree canopy tends to be .

Increased biodiversity may support better  by enhancing the restorative experience and also via the immunoregulatory benefits of microbial 鈥溾�� 鈥� microorganisms that helped shape our immune systems but which have been largely .

Green spaces with tree canopy are settings where communities can come together to watch birds and other animals, which can also be catalysts for new conversations and developing feelings of community belonging in the neighbourhoods where we live 鈥� just ask .

So, what about the grass?

Our research did not show a mental health benefit from more bare grassed areas. This does not mean grass is bad for mental health.

Previous research suggests adults are less likely to wander in green spaces that are relatively . This may also be partly attributable to preferences for green spaces with , such as parks that mix grass with tree canopy.

Furthermore, large areas of bare grass in cities can make built environments more spread-out and less dense. Without tree canopy to shield from the midday sun, this may increase the likelihood of people using cars for short trips instead of walking through a park or along a footpath. The result is missed opportunities for physical activity, mental restoration, and impromptu chats with neighbours. Previous work in the United States suggests this might be why .

Large open areas of grass can be awesome for physical activity and sport, but let鈥檚 make sure there is also plenty of tree canopy too, while also thinking about ways to get more people outdoors in green spaces. Here are .

Making Australia greener and healthier

As the density of Australian cities continues to increase and more of us live in apartments and/or work in high-rise office blocks, it is great to see strategies to invest in tree cover and urban greening more generally across Australia. Cities with such plans include , , , , , and .

You can get involved and have some fun at the same time too. Lots of evidence says . So why not grab a mate and spend a couple of hours planting a tree on July 28 for !

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