In Australian cities, infill development and urban sprawl are leading to the loss of vegetation and the ecosystem services that plants provide. As warming associated with urban development and climate change intensifies, vulnerable social groups will be at greater risk of heat-related morbidity and mortality. There is an urgent need to address this problem without increasing emissions of greenhouse gases. The strategic development of urban green infrastructure can help achieve this goal. This report reviews the Australian and international scientific and technical literature quantifying the cooling and energy-saving benefits of three types of green infrastructure: shade trees; green roofs; and vertical greening systems (VGS) (green walls and facades).
International research demonstrates that green infrastructure can reduce surface and ambient temperatures at the micro-scale. However, there is limited research using experimental methods and validated modelling to determine the magnitude of cooling and energy-saving benefits that may be achieved at local-to city-wide scales, particularly for green roofs and VGS. The greatest thermal benefits are achieved in climates with hot, dry summers, particularly if water is available to maintain canopy health and evapotranspiration. Despite this, green infrastructure is not well established in Australia. There is a pressing need for experimental research quantifying the effects of specific plant traits, vegetation health, water availability and soil/substrate composition on the thermal performance of shade trees, green roofs and vertical greening systems. Research to determine the extent, location and mix of green infrastructure required to produce optimal cooling and energy-savings at neighbourhood and city-wide scales, in the diverse climates and ecosystems of Australian cities is also required.