Urban landscapes could be cooled by up to 3.5 degrees using a QUT-developed AI-based tool that optimises where trees and which species are planted to make cities cooler, greener and more resilient in the face of climate change.
Choice of tree as important as its placement for maximising temperature reduction
Study gives framework for designing vegetation that reduces heat stress
Four tree species chosen for their thermal performance, adaptability to conditions and canopy shapes
First author QUT PhD researcher Abdul Shaamala (pictured above) from QUT's School of Architecture and Built Environment said city planners could use the tool to prioritise species and location of tree plantings in urban areas at risk of overheating during extreme heat.
"The urban heat island effect - where built-up areas experience higher temperatures than surrounding areas - increases heat discomfort, energy consumption, and public health risks, especially for the elderly, children and low-income communities," Mr Shaamala said.
"The strategic placement of urban trees chosen for their shade and cooling capacities is a promising way to harness their capacity to moderate microclimatic extremes.
"Conventional greening initiatives bring the benefits of shade and evapotranspiration (cooling of the air by releasing water vapour) but often use static, aesthetic-driven plantings that don't address the complexity of urban heat flows, nor the crucial influence of species-specific traits and localised climatic conditions.
"To address this, we developed a framework to design urban greening strategies that would be responsive to dynamic and intensifying outdoor heat stress.
"We used AI to create the framework incorporating the Universal Thermal Climate Index, which measures the 'feels like' temperature for humans, with the functional traits of different tree species to improve resilience of microclimates in the built environment."
The team conducted the study in extreme summer conditions in a recently developed suburb on Bribie Island, Queensland, chosen as an ideal location for simulating new greening strategies.
Mr Shaamala said the study had incorporated four tree species chosen for their thermal performance, adaptability to the conditions of the study area, and canopy shapes, which influence their cooling potential and suitability for urban planting.
The tree species are:
Ash (Fraxinus griffithii) a medium-sized deciduous tree with rounded canopy.
Brush box (Tristania Conferta), a dense evergreen species with a dome-shaped, uniform canopy.
Yellow wood (Podocarpus elongatus), a compact evergreen species with a narrow, upright canopy.
Queen palm (Syagrus romanzoffiana) a tall palm species with a slender trunk, characterised by a fan-shaped canopy which performs well in Brisbane's subtropical climate. All four species were selected to bring a mix of canopy shapes and cooling functions.
"Using a specialised algorithm to explore combinations of tree placement and species assignment, we found the optimised configuration achieved a 22 per cent reduction in areas more than 39oC, an 18 per cent increase in the thermally comfortable zones and cooling benefits of up to 3.5oC," Mr Shaamala said.
The QUT team comprised Mr Shaamala, Professor Tan Yigitcanlar, and Dr Dan Nyandega from the School of Architecture and Built Environment, and Dr Alireza Nili, from the School of Information Systems.
The study, Algorithmic urban greening for thermal resilience: AI-optimised tree placement and species selection was published in Cities.
