Characterising Green Roof Uptake in a Southern Hemisphere City: Melbourne, Australia

Green roofs are being installed in urban areas worldwide to mitigate the negative effects of urbanisation and climate change. Cities outside the temperate zone of Europe and North America may be lagging behind in green roof uptake but information on the number and area of green roofs is rarely available. This can hinder the assessment of the effectiveness of local greening policies. Using a timeseries of high-resolution imagery, this study assessed the abundance, distribution, and characteristics of green roofs in Melbourne, Australia, from 2000 to 2019. We found that most green roofs were located within 5 km of the city centre on mid (3 - 5 stories) to high-rise (5+ stories) apartment buildings and offer recreational space for their residents. Further, on average, only one third of each green roof was covered by vegetation which may negatively impact the delivery of important ecosystem services, such as stormwater retention or cooling. The results of this study benchmark the rate of Melbourne’s green roof uptake and characteristics of their design and can be compared with other cities. It also suggests that further informs decisionmakers about the relative effectiveness of existing green roof policies or the need for additional initiatives. • 224 green roofs identified in Melbourne from 2000 to 2019 • Installation surged post-2014, following policy and guideline releases • Most green roofs are on new high-rise buildings for residential recreation • Vegetation covers only a third of roof area, limiting environmental benefits • Results benchmark Melbourne's uptake and enable international comparison