Trees on Brisbane streets: study reveals shady suburbs

Of the 210 site images obtained in the study, 263 trees were identified as belonging to the footpath, with 48 species classified.

These included trees planted privately by local authorities, as well as trees planted in newly developed suburban areas.

Leopard trees, camphor laurel, Indian beech, golden penda and cassia trees were among the best species to provide shade on the city streets.

“But if you want the best trees (for shade), you’ll probably choose the ficus (fig) species,” Downs said.

“The problem is they are very invasive and their roots get into the infrastructure.”

First and foremost, 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.

Research by Dorina Poggiani and Sean Patton at the University of Queensland has revealed a more critical view of providing shade throughout the city.

He counted trees in three Brisbane suburbs with different average income levels, from low (Diagon) to middle (Riverhills) to higher (Parkinson). The results mirror similar studies of urban environments around the world that have found differences in street coverage by income.

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“The richer the suburb, the more lush it tends to be,” Poiani said. “It’s kind of a perverse result because in poorer suburbs people need trees more because they’re more reliant on public transport.

“In the wealthier suburbs, people have cars and don’t have to walk as much to get around.”

While Downs’ research focused on the health effects associated with providing shade, Pojani and Patton approached tree cover from the perspective of convenience and availability.

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

“In this case, we looked at street trees as providing transportation infrastructure (and) providing shade to allow people to get from their home to the bus stop.”

Brisbane’s bus stops can be particularly hostile, especially in the 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 are needed at bus stops.

So who is responsible for the mismatched shades?

“It’s a good question and we’re looking into it more. But we assume that in wealthier suburbs, people are better organized and tend to be better educated,” Pojani said.

“We know from other studies that, in general, (rich) people tend to dominate social activities in a city.

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

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

While specific locations have not yet been identified, she said areas with less tree cover will be targeted for future street planting and residents can contact the council to request a tree be planted on their curb.

“Since January 1, 2023, the council has been contacted 3,372 times to request street planting,” she said.

Downs has a simple explanation for why this is important.

“We need a city to live in, and to me a city to live in is a city that has good shade.”

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