What the tree cover in your suburb’s streets says about where you live

In Brisbane’s inner south-west, curled around the river between Indooroopilly and Chelmer, Graceville is the epitome of a “leafy suburb”.

The houses along its main street, Honour Avenue, are lined with large camphor laurel trees, some said to be over 100 years old. Across the road, broad-leaved paperbark trees run alongside the railway line, stretching towards the Walter Taylor Bridge.

There is extra charm at this time of year, with vibrant bursts of colour from the jacaranda trees breaking through the greenery. It’s a beautiful neighbourhood, but it’s not just aesthetics that make Graceville a good place to live.

Bell Terrace in Graceville is among Brisbane’s shadiest streets.Credit: Courtney Kruk

A 2022 University of Southern Queensland study that rated footpaths in 10 Brisbane suburbs for ultraviolet radiation exposure found three Graceville Streets – Honour Avenue, Bell Terrace and Laurel Avenue – were among the city’s shadiest.

Forest Lake, Annerley and Coorparoo also enjoyed plenty of shade, with four, five and three streets on the list, respectively.

Radiation scientist and study lead Nathan Downs has been researching Queensland’s UV index and how it influences our physical environment for more than 20 years.

“Queensland has the highest skin cancer rates in the world, typically around south-east Queensland,” Downs said.

“[With this project] we really wanted to know what type of trees were best, how those seeds were planted, and what their canopy structure was like.”

From 210 site images surveyed for the study, 263 trees were identified as belonging to a footpath, with 48 species classified.

These included trees planted by local government, privately, and established trees left standing in newly developed suburban areas.

A well-shaded street, such as this one in Graceville, is defined by the presence of established, mature trees, says radiation expert Nathan Downs.Credit: Courtney Kruk

Leopard trees, camphor laurel, Indian beech, golden penda and cassia trees were among the top species providing shade along the city’s streets.

“But if you wanted to have the best trees [for shade], you’d probably be going for a ficus [fig] species,” Downs said.

“The problem with those is they’re very invasive, and the roots get into infrastructure.”

Above all, what defines a well-shaded street is the presence of established, mature trees. “The best time to plant a tree was 30 years ago, and the second-best time is today,” Downs said.

Radiation scientist Nathan Downs –pictured holding a whole-sky imaging device – has spent more than 20 years studying Queensland’s UV index. Credit: University of Southern Queensland

Over at the University of Queensland, research by Dorina Pojani and Sean Patton revealed a more critical outlook on shade provision across the city.

It counted trees in three Brisbane suburbs of varying average income levels, from low (Deagon) to middle (Riverhills) and higher (Parkinson). The results mirrored similar studies of urban environments around the world, finding differences in street cover predicated on income.

“The wealthier the suburb, the lusher it tends to be,” Pojani said. “It’s sort of a perverse outcome because in poorer suburbs, people need trees more because they’re more reliant on public transport.

“In wealthier suburbs, people have cars, and they don’t need to walk to transit as much.”

While Downs’ research focused on health outcomes associated with shade provision, Pojani and Patton approached tree cover from an amenity and accessibility perspective.

“We need trees for many reasons: they clean the air, they allow for better water circulation, they even allow animals to move through the city.

“In this instance, we have looked at street trees as providing transport infrastructure [and] providing shade for people to be able to get from their home to a bus stop.”

Brisbane’s bus stops can be particularly hostile, especially in summer. In 2020, Brisbane City Council surveyed residents to find out what they valued and what concerned them about street and park trees. Most said more shade trees at bus stops were needed.

Dorina Pojani says while beautiful in spring, jacaranda trees don’t provide enough shade for Brisbane, which needs denser foliage.Credit: Courtney Kruk

So who is responsible for shade discrepancies?

“It’s a good question and something we’re researching more. But our speculation is that in wealthier suburbs, people are better organised and tend to be better educated,” Pojani said.

“We know from other research that generally, [wealthy] people tend to dominate public participation activities in the city.

“People living in poorer suburbs work more jobs and have less time to contact council. They may not even have the confidence or human resources that wealthier suburbs do.”

Brisbane City Council chair of environment, parks and sustainability Tracy Davis said 79 per cent of residents lived in a suburb with more than 20 per cent tree cover, and more than 11,000 street trees were planted last financial year.

While specific locations have not been decided, areas with less tree cover would be targeted for future street planting, and residents could contact council to ask for a tree on their verge.

Since January 1, 2023, the council has been contacted 3372 times for street tree requests.

Downs has a simple explanation for why this matters.

“We want a city that’s liveable, and for me, a city that’s liveable is one that has good shade.”

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