Data shows Brisbane’s reputation as one of Australia’s greenest cities is well deserved. However,experts have questioned whether the city has the right mix when it comes to public open space.

Professor Nicholas Osborne has been studying the health benefits of open space,particularly green space,at the University of Queensland’s school of public health.

Osborne said that,from a health point of view,the benefits of having access to public green space were clear.

There was vitamin D absorption from the sun – a third of Australians were deficient in vitamin D,Osborne said – along with the exercise and psychological benefits.

“One of the greatest determinants of health is your postcode,more than your genetic code. If you’re richer,you’re more likely to be healthy,” he said.

“In Sydney,you see that gradient from east to west across the city. The further west you go,the further down you go on the socioeconomic spectrum and then you see the rise of those chronic diseases.

“So,how do you unpick that? That’s the trick. Is it just that you’re richer,leading to better health,or is it the green space you’re in? What we try to do as researchers is unpick that kind of triangle between socioeconomic status,your exposure to green space and your health.”

Osborne admitted experts still had a lot to learn and it was increasingly clear the type of public space mattered as much as its accessibility (more on that later).

“We’re pretty happy with that notion that green space is good for you,but we still don’t know how it works,” he said.

“We could save millions of dollars if we just found out it’s physical exercise,or 90 per cent of it is physical exercise,and we just build running tracks everywhere and have parks that are designed to get people physically active.

“I think there’s probably more to it than that,but we haven’t accumulated that evidence yet.”

Whatever the health attributes of green space,Brisbane appeared to be doing pretty well on the accessibility front.

A Brisbane City Council spokeswoman said the goal,under its city plan,was for all Brisbane residents to be within a 750-metre walk of a park or green space.

“The vast majority of Brisbane residents currently fall within this 750-metre distance,” she said.

“As the population of Brisbane continues to grow,council continues to plan for new parks in areas where this aim is not met.”

But research undertaken by the Australian Urban Observatory,based at the RMIT Centre of Urban Research in Melbourne,shows greater Brisbane is inequitable when it comes to access to public open space.

According to its2021 Liveability Report for Brisbane,which will be released this week,Brisbane ranked second among Australia’s largest 21 cities,behind Townsville and ahead of Bendigo.

But the study also showed an uneven spread:a patchwork of results,as the interactive map above shows,with some of themore car-dependent suburbs faring the worst.

“Brisbane is one of the greenest cities in the country,” Osborne said.

“Part of it is we live in the subtropics and things really grow quickly here – there’s plenty of sunshine at this latitude,where you’re in the northern climes,but it’s also because some of the cities to the south are older,and they weren’t quite as planned.”

It was not just ease of natural growth,Osborne said,but the floral diversity in the subtropics that put Brisbane in good stead.

Osborne said evidence was mounting that physical access to biodiversity was a key health benefit,meaning just being around certain plants could improve one’s life.

“There’s been a rise in allergic diseases over the past 20 years and nobody really knows why,” he said.

“One of the things we have noticed is that people living in low-income countries that don’t take antibiotics,that have large families,and live close in proximity to domesticated animals,don’t seem to have these diseases like asthma,food allergy,rhinitis,hay fever.

“We living in the West who might have small families,or might live alone,take loads of antibiotics,don’t get out into green space that much,don’t have a cow in the shed – our immune system seems to be compromised because of this and it starts looking for things to attack.

“Ten thousand years ago,there were plenty of bugs that we came in contact with that our immune system had to attack.

“Now,instead of going looking for those bugs,it attacks a peanut protein,for instance,and thinks it’s a bad thing.

“Then,you develop an allergy to peanuts.”

Hence the need for more exposure to nature,Osborne said.

“There are theories that your contact with green space changes your flora,living in both your gut and on your skin,to the extent that it reduces what we call your inflammasomes,” he said.

“So all those sorts of diseases that are related to inflammation – things like diabetes,heart disease,mental illness,asthma – which,of course,are the big,chronic diseases that we’re dealing with in high-income countries.”

Greg Mews,a lecturer in urban design and town planning at the University of the Sunshine Coast,said the positive effects were not just physical.

“There’s a mountain of evidence that it’s good for your social,mental and physical health and wellbeing,” Mews said.

“It’s pretty obvious that having biodiversity and green,lush areas around is comforting and calming and has therapeutic effects,” he said.

“They are synergistic properties,which is a fancy word for all the sensory experience that you get in a natural setting that you don’t get necessarily in the built environment.”

While the data shows Brisbane doing pretty well on these fronts,an increasing population will present major challenges,going forward.

For example,as Brisbane’s population grows,private green space – the suburban backyard – will continue to shrink.

Suburban Futures co-founder Ross Elliott,the chairman of the Lord Mayor’s Better Suburbs Initiative,said that was a trend that needed a response.

“Back in the day when everyone had their own backyard,you had your own private open space,” he said. “The pressure will be on now to make more use of what’s there.”

Mews said as backyards continued to shrink,demand for good public parks would only rise.

“With the overall housing crisis,and as we’re trying to densify and have more infill,we definitely have to look at public open spaces,and how we’re preserving certain particular lots for either pocket parks,neighbourhood parks or recreational parks,” he said.

Those parks would need to be easily accessible,Mews said,and in established suburbs experiencing a lot of infill development,that could be challenging.

But not all green space is created equal.

The AUO data showed Brisbane was on par with other major Australian capital cities,with 41 per cent of residents within 400 metres of spaces of at least 1.5 hectares in size.

Elliott said while Brisbane had “quite a lot” of open space,the issue was that not all of it was terribly well utilised.

“There are examples right across the south-east,not just within Brisbane,of open spaces being most frequently used by the mowing contractor,because if it’s not particularly attractive,people will look at it but won’t make use of it,” he said.

“So the challenge is working out what will encourage people to make the most use of that open space,and I think the days of thinking of it as simply just a place of grass and trees is giving way to looking for more active built-form additions.”

Those came in the form of barbecues,exercise equipment and even commercial activities such as kiosks,Elliott said.

“We’re going to have to come to a realisation that,if you’ve got a playground that’s fantastically busy because parents are bringing their kids,or the kids are dragging parents there,then putting a concession into that space – maybe it’s a coffee shop,or it’s a bistro or whatever it is;something that pays some rent back to the community to help with the upkeep and the capital works – is a better way of doing it than simply increasing rates,” he said.

“Public open space has barbecue areas,playing gyms,all sorts of things. It’s not just a case of throwing down some grass and some trees and maybe a bench here and there.

“The appetite is for so much more.”

Osborne said a lot of thought had to be put into new master-planned communities,as south-east Queensland continued to unlock more land to house its booming population.

“Once they’re built,they’re not going to get unbuilt. So maybe people need some guidance around that.”

And south-east Queensland was well positioned to learn from Sydney’s mistakes.

“Do we allow what’s happened in areas of western Sydney,where people have built houses with black roofs,every inch of the block covered by a house with no green space?” Osborne said.

“Has someone informed the people who are going to live in these houses that maybe that’s not such a great idea?

“Is it just a trend that we’re going through?”

This article was produced in collaboration with the Australian Science Media Centre,with support from the Walkley Foundation-administered Meta Public Interest Journalism Fund.