Benchmarking Tree Canopy in Sydney's Hot Schools

BENCHMARKING TREE CANOPY IN SYDNEY’S HOT SCHOOLS OCTOBER 2020 WESTERN SYDNEY UNIVERSITY AUTHORS Sebastian Pfautsch, Agnieszka Wujeska-Klause, Susanna Rouillard Urban Studies School of Social Sciences Western Sydney University, Parramatta, NSW 2150, Australia With respect for Aboriginal cultural protocol and out of recognition that the campuses of Western Sydney University occupy their traditional lands, the Darug, Tharawal (also historically referred to as Dharawal), Gandangara and Wiradjuri people are acknowledged and thanked for permitting this work in their lands (Greater Western Sydney and beyond). This research project was funded by Greening Australia. SUGGESTED CITATION Pfautsch S., Wujeska-Klause A., Rouillard S. (2020) Benchmarking tree canopy in Sydney’s hot schools. Western Sydney University, 40 p. DOI: https://doi.org/10.26183/kzr2-y559 ©Western Sydney University. www.westernsydney.edu.au October, 2020. Image credits: pages 18 and 23 ©Nearmap, other images from istock.com. 2 Western Sydney University Urban parks and school yards with adequate vegetation, shade, and green space have the potential to provide thermally comfortable environments and help reduce vulnerability to heat stress to those active within or nearby. However, in order to provide this function, outdoor spaces, including parks and schoolyards, must be designed within the context of the prevailing urban climate and projected future climates. JENNIFER K. VANOS (ENVIRONMENT INTERNATIONAL, 2015) westernsydney.edu.au 3 WESTERN SYDNEY UNIVERSITY SUMMARY This project identified the 100 most vulnerable schools to heat in Greater Western Sydney using a newly developed Heat Score. The Heat Score combines socio-economic information that captures exposure, sensitivity and adaptivity of local communities to heat with environmental data related to surface and air temperatures of urban space. Following the identification of the 100 schools, Additional tree plantings will provide high-resolution aerial imagery was used to microclimatic benefits. However, the present remotely measure a range of attributes at study reveals that a dual approach is each school. These attributes included the necessary to increase canopy cover among area covered by buildings and open space, the target schools that differentiates between as well as the area of tree canopy cover and needs and opportunities. manmade shade structures. We determined the size of close to 5,000 individual objects to Catholic and independent schools have the establish a benchmark of shade in Sydney’s highest need for additional tree canopy cover hot schools. as their current cover is low. These schools tend to have less open space available for Key findings: plantings. Successful strategies will require establishing low numbers of carefully selected » Mean area covered by the 100 schools is trees at strategic planting locations to deliver 23,000 m². the greatest local shading and cooling » On average 18% of that area is shaded benefits. » Tree canopy cover makes up the majority Public schools offer the greatest opportunities (15%) of the shaded area. for mass planting of additional trees as they » Tree canopy cover increases with the area have large areas of open space available. covered by a school. Planting sizeable clusters of trees will provide the greatest cooling benefits not only for » Public schools tend to cover larger areas the school but generate microclimate and and thus have more tree canopy cover environmental benefits for the surrounding compared to Catholic and independent communities. schools. » Urban Heat Island effects were reduced Analyses provided in this report will assist when the area of shade was increased. the development of the most effective tree planting strategies for each of Sydney’s 100 hot schools. 4 Western Sydney University TREE CANOPY IN SYDNEY’S HOT SCHOOLS SUMMARY westernsydney.edu.au 5 WESTERN SYDNEY UNIVERSITY CONTENTS SUMMARY 4 CONTENTS 6 1. BACKGROUND 8 2. STUDY GOALS 10 3. METHODOLOGY 11 3.1 Identification of 100 Hot Schools 11 3.2 Tree Canopy Cover Analysis 15 4. RESULTS 18 4.1 Available Space 18 4.2 Shade in Schools 22 4.3 Tree Canopy Cover 23 5. CONCLUSIONS AND RECOMMENDATIONS 29 5.1 Small Schools 29 5.2 Large Schools 29 5.3 General Remarks 29 6. REFERENCES 31 7. SCHOOL DATA 32 6 Western Sydney University TREE CANOPY IN SYDNEY’S HOT SCHOOLS westernsydney.edu.au 7 WESTERN SYDNEY UNIVERSITY 1. BACKGROUND The climate of New South Wales is changing. A clear long-term trend of increasingly warmer air temperatures is documented in the climate records for this state (Figure 1). The Bureau of Meteorology reported that the 11 hottest years recorded in Australia have all occurred in the past 15 years. The hottest year on record for Australia was 2019 where mean air temperatures were 1.92°C above the long-term mean (1961-1990). 2.0 1.5 ) 1.0 0.5 0.0 -0.5 Mean air temperature anamoly (C Mean air temperature -1.0 -1.5 1950 1960 1970 1980 1990 2000 2010 2020 Year FIGURE 1: Long-term trend in anomalies of air temperatures (i.e., the deviation of the mean annual air temperature from the long-term (1961-1990) mean) in NSW, Australia. Years with cooler than average temperatures are shown in blue, those where average temperatures were warmer are shown in red. The 11 hottest years have been recorded since 2005. The black line shows the 15-year moving mean. Data was downloaded from the Bureau of Meteorology. Increasing heat will impact the learning inside schools is a key concern of the outcomes but also the physical health Department of Education. and safety of school children. The clear negative relationship between hot classroom The general unpreparedness of schools to temperatures and learning outcomes has deal with climate change effects, especially been documented in a number of countries that of increasing summer heat was (Seppänen et al., 2006; Wargocki et al., highlighted in the Cool Schools report from 2010; Goodman et al., 2018). Classroom Western Sydney University (Madden et temperatures can be regulated using air al., 2018) (Figure 2). The report provided a conditioning systems and the 500 million- comprehensive overview of current policies dollar ‘Cooler Classrooms Program’ of and practices around heat and learning the NSW Government (https://www. in Australia and reviewed building codes, schoolinfrastructure.nsw.gov.au/programs/ standards, sustainability education and cooler-classrooms.html) is a clear indicator innovative trends in building and landscape that providing optimal learning temperatures design. 8 Western Sydney University TREE CANOPY IN SYDNEY’S HOT SCHOOLS value of learning activities in the outdoor given the clear relationship between heat and space of school environments is increasingly learning outcomes but also heat and physical recognised (Harris, 2017). health, school children in Greater Western Sydney are disadvantaged in achieving the As a result of rising air temperatures, schools same academic goals as their peers in the east will have to find solutions to deal not only with only because the environmental framework hot classrooms, but importantly, also develop conditions are less favourable. smart strategies how to provide thermally safe outdoor environments. Yet, lowering One strategy to reduce this effect is to outdoor temperature in school environments increase the canopy cover across the schools is far more difficult to achieve than cooling of Greater Western Sydney. Yet, there is no classrooms. Buildings and surfaces that make available information on canopy cover in up school infrastructure are dominated by schools of the Sydney Basin. This fact makes hard, impervious materials with low albedo it extremely difficult to develop strategies (i.e., the reflectivity of the material) and high and programs that aim to retain and expand thermal mass (i.e., the capacity to store solar canopy cover in schools throughout the energy). These materials generally absorb region. Which are the most vulnerable schools and re-radiate large amounts of solar energy to heat? Could it be that those schools located (Ma et al., 2017) leaving unshaded school in the hottest parts of Greater Western outdoor environments hot during summer. Sydney already have maximum tree canopy In contrast, pervious surfaces and green cover and thus other means of cooling must infrastructure, especially well-hydrated be investigated? Could the origin of high lawns, shrubs and trees can provide cooling vulnerability to heat be a result of socio- through evapotranspiration. Tree shade economic, rather than purely environmental FIGURE 2: The Cool Schools report by Madden reduces surface temperatures and has been drivers, or a mix of them? Finding answers to and colleagues can be downloaded at: identified as one of the most cost-effective these questions was at the core of the present https://doi.org/10.26183/5b91d72db0cb7. cooling infrastructures in schools (Antoniadis research. et al., 2016). However, contemporary outdoor Here we introduce a new method to rank the school environments can lack these important schools of Greater Western Sydney according elements for cooling because they incur The majority of learning takes place inside to their vulnerability to heat. This method does maintenance costs and if not managed well, the classroom. However, a number of key not differentiate between public and private, can become health hazards. school activities, like sport and play take primary or secondary schools. Exposure to increasing summer heat is a shared issue among place outside the

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