Guide to Climate-Smart Playgrounds: Research Findings and Application

Outdoor play is vital for positive socialisation and development of children including cognitive, psychological, and physiological benefits. Playing outdoors increases attention, creative thought processes and problem-solving skills as well as combating obesity, mental health problems and improving social skills of children. Encouraging and supporting outdoor play is particularly important today, where the daily time interval children are engaging in physical activity is contracting. However, the lack of shade and hot playground equipment make it unsafe for children to enjoy playgrounds in summer. This situation is particularly problematic in times where summer heat is increasing as result of climate change, which already limits the time for safe outdoor play. Now more than ever is it necessary to start building climate-smart playgrounds. This report has two parts. Part 1 establishes the facts around heat in playgrounds. We document surface, air and feels like temperatures in public playgrounds across the Cumberland Local Government Area. All playgrounds were visited repeatedly during warm and hot conditions in the summer of 2019/20 and 2020/21. Part 1 also provides systematic analyses of surface temperatures of SBR, EPDM, TPO, synthetic turf and real grass. In Part 2 we describe the process, outputs and outcomes of a playground transformation at Memorial Park in Merrylands. The playground is in the Local Government Area of Cumberland City Council in the geographic centre of Sydney. With support from the NSW Government, Cumberland City Council, industry partners and inputs from a range of stakeholders, we created Australia’s first dedicated UV-smart Cool Playground. Since October 2020, the playground is enjoyed by the local community. Research data showing the avoided heat, improved thermal comfort and reduced exposure to UV-A and UV-B are provided and demonstrate the functionality of the playground

Cool Roads Trial 2021

Intensifying summer heat and associated Urban Heat Island Effects are a risk to public and environmental health. They contribute to higher energy consumption and associated greenhouse gas emissions in cities. Across Greater Western Sydney, home of the fastest growing urban population in Australia, increasing heat is recognised as the largest risk to local populations and economies. A range of interventions across the region aim at mitigating the negative impacts of heat. The Cool Roads Trial is one of these interventions. It addresses the contribution of unshaded road and carpark surfaces to local heat island effects. In March 2020, 14,700 m2 of road and carpark surfaces were coated with a highly reflective asphalt emulsion in the local government areas of Blacktown, Campbelltown and Parramatta to reduce surface temperatures of pavements. The trial was accompanied by an environmental monitoring program. The program used measurements of surface, air and black globe temperatures to document the effectiveness of the surface coat on cooling. Data were collected between February 2020 and March 2021 using a full-factorial design with paired impact and control sites. Results showed that surface temperatures of unshaded coated pavements were on average 6°C and at maximum 11°C cooler compared to uncoated pavements. Tree shade reduced temperatures of uncoated surfaces by 20°C and that of coated surfaces by 14°C leading to identical surface temperatures in the shade on coated and uncoated surfaces. Surface coating did not systematically reduce air temperature during the day or night. Back globe temperatures during sunny days increased by 2.7°C on coated compared to uncoated sites as a result of increased reflectivity of the surface. The higher exposure to reflected solar incident radiation resulted in lower thermal comfort in the sun on coated surfaces. The Cool Roads Trial established important information for the management of heat in Western Sydney and beyond. Increasing albedo of roads and carparks will help reduce surface Urban Heat Island Effects due to lower surface temperatures. Ambient air temperatures were not lowered as a result of coating roads and carparks, which can potentially be a matter of scale. The Cool Roads Trial worked at the microscale where air cooling benefits could be masked by continuous mixing of local with surrounding air masses. The range of thermal effects documented in this report make it clear that mitigating the impacts of urban heat will require a broad suite of solutions. A clear definition of desired thermal outcomes will be necessary on a case-by-case basis. Only once thermal outcomes are defined can resilience of urban populations, infrastructure and ecosystems against intensifying summer heat be improved effectively

The best urban trees for daytime cooling leave nights slightly warmer

Summer air temperatures will continue to rise in metropolitan regions due to climate change and urbanization, intensifying daytime and nighttime air temperatures and result in greater thermal discomfort for city dwellers. Urban heat may be reduced by trees which provide shade, decreasing air and surface temperatures underneath their canopies. We asked whether tree height and canopy density can help to identify species that provide greater microclimate benefits during day and night. We also asked if increased canopy cover of street trees provides similar microclimate benefits. We used continuous measurements of near-surface air temperatures under 36 park trees and from two urban streets to assess these questions. In the park, trees were grouped according to their height (20 m) and canopy density (low, high), while the effect of canopy cover was tested using streets with high (31%) and low (11%) cover. Daytime near-surface air temperature declined with increasing height and canopy density providing significant cooling benefits. However, this trend was reversed at night when tall trees with dense canopies restricted longwave radiative cooling and trapped warm air beneath their crowns. High canopy cover of street trees reduced daytime air temperatures more, resulting in a lower number of days with hot (>35 °C) and extreme (>40 °C) air temperatures compared to the street that had low canopy cover. These findings suggest that tree species and streetscapes with dense canopy cover improve local thermal conditions during the day but do not seem ideal to allow for nighttime cooling, creating potential discomfort for residents during hot summer nights. Our results indicate that classifying trees using a simple metric can assist in selecting tree species that can alleviate the local negative effect of urban heat during the day, but at the same time, their effect in preventing optimal longwave radiative cooling during the night must be factored into planting strategies

Benchmarking Tree Canopy in Sydney's Hot Schools

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, high-resolution aerial imagery was used to remotely measure a range of attributes at each school. These attributes included the area covered by buildings and open space, as well as the area of tree canopy cover and manmade shade structures. We determined the size of close to 5,000 individual objects to establish a benchmark of shade in Sydney’s hot schools. Key findings: » Mean area covered by the 100 schools is 23,000 m². » On average 18% of that area is shaded » Tree canopy cover makes up the majority (15%) of the shaded area. » Tree canopy cover increases with the area covered by a school. » Public schools tend to cover larger areas and thus have more tree canopy cover compared to Catholic and independent schools. » Urban Heat Island effects were reduced when the area of shade was increased. Additional tree plantings will provide microclimatic benefits. However, the present study reveals that a dual approach is necessary to increase canopy cover among the target schools that differentiates between needs and opportunities. Catholic and independent schools have the highest need for additional tree canopy cover as their current cover is low. These schools tend to have less open space available for plantings. Successful strategies will require establishing low numbers of carefully selected trees at strategic planting locations to deliver the greatest local shading and cooling benefits. Public schools offer the greatest opportunities for mass planting of additional trees as they have large areas of open space available. Planting sizeable clusters of trees will provide the greatest cooling benefits not only for the school but generate microclimate and environmental benefits for the surrounding communities. Analyses provided in this report will assist the development of the most effective tree planting strategies for each of Sydney’s 100 hot schools

Outdoor playgrounds and climate change : importance of surface materials and shade to extend play time and prevent burn injuries

Surfaces in outdoor playgrounds get hot in the sun and can cause serious skin burns in children. In-situ measurements from 10 playgrounds in Sydney showed that the maximum and average surface temperatures of sunexposed playground equipment and flooring surfaces were frequently above skin contact burn thresholds. Black and dark-coloured wet pour rubber and synthetic turf were the hottest floor materials, all having maximum surface temperatures (Ts_max) > 80 ◦C. A blue rubber dolphin was the hottest piece of play equipment, with a Ts_max of 91.8 ◦C. A systematic assessment of common synthetic flooring materials exposed to full sun showed notable differences in Ts_max between material types and colour-tones. Synthetic turf with 40 mm long grass blades (STlng-GR) was the hottest material (Ts_max = 84.5 ◦C), followed by dark blue styrene butadiene rubber (SBRD-BL, Ts_max = 81.1 ◦C), dark green ethylene propylene diene polymer (EPDMD-GR-2, Ts_max = 77.8 ◦C), dark brown thermoplastic vulcanizate (TPVD-BR, Ts_max = 71.8 ◦C), and intermediate blue thermoplastic polyolefin (TPOI-BL, Ts_max = 65.0 ◦C). All these materials were hot enough to cause contact burns on typical, warm summer days when children are likely to visit outdoor playgrounds. Surface temperatures were significantly reduced in the shade and never reached burn threshold temperatures. Selection of appropriate material type and colourtone, together with the provision of shade can remove the hazard risk for contact skin burns from outdoor playgrounds. Results of this work will assist playground designers and managers to provide safer places for our children to play longer in increasingly warmer summers

Nitrogen and Phosphorus Retranslocation of Leaves and Stemwood in a Mature Eucalyptus Forest Exposed to 5 Years of Elevated CO2

Elevated CO2 affects C cycling processes which in turn can influence the nitrogen (N) and phosphorus (P) concentrations of plant tissues. Given differences in how N and P are used by plants, we asked if their stoichiometry in leaves and wood was maintained or altered in a long-term elevated CO2 experiment in a mature Eucalyptus forest on a low P soil (EucFACE). We measured N and P concentrations in green leaves at different ages at the top of mature trees across 6 years including 5 years in elevated CO2. N and P concentrations in green and senesced leaves and wood were determined to evaluate both spatial and temporal variation of leaf N and P concentrations, including the N and P retranslocation in leaves and wood. Leaf P concentrations were 32% lower in old mature leaves compared to newly flushed leaves with no effect of elevated CO2 on leaf P. By contrast, elevated CO2 significantly decreased leaf N concentrations in newly flushed leaves but this effect disappeared as leaves matured. As such, newly flushed leaves had 9% lower N:P ratios in elevated CO2 and N:P ratios were not different in mature green leaves (CO2 by Age effect, P = 0.02). Over time, leaf N and P concentrations in the upper canopy slightly declined in both CO2 treatments compared to before the start of the experiment. P retranslocation in leaves was 50%, almost double that of N retranslocation (29%), indicating that this site was P-limited and that P retranslocation was an important mechanism in this ecosystem to retain P in plants. As P-limited trees tend to store relatively more N than P, we found an increased N:P ratio in sapwood in response to elevated CO2 (P < 0.01), implying N accumulation in live wood. The flexible stoichiometric ratios we observed can have important implications for how plants adjust to variable environmental conditions including climate change. Hence, variable nutrient stoichiometry should be accounted for in large-scale Earth Systems models invoking biogeochemical processes

Despicable Urban Places: Hot Car Parks

Cities are warmer than surrounding non-urban areas. Climate models predict that metropolitan centres will become even warmer due to the dual impacts of global warming and densification. However, the outer fringe zones of metropolitan centres will also become warmer as a consequence of urban expansion that requires replacing green and open spaces like pastures or bushland with grey infrastructure such as roads and buildings. Limiting the warming effect of urban expansion is possible. It requires dedicated heat-responsive planning and design strategies being applied systematically and at scale. But where should planners and developers start to effectively reduce urban heat? At-grade car parks are an ideal starting point. They represent the ‘low-hanging fruit’ for urban cooling efforts. While unavoidable today and in the near future, at-grade car parks are predominately unshaded; made from black, heat-retaining asphalt; widespread and fairly uniform; and often large in size. Changes to current designs of at-grade car parks can therefore have a big impact. A number of strategies to effectively reduce surface heat of car parks are commercially available. Cooling car parks not only addresses their status as local heat islands, but it also leads to lower ambient air temperatures in downwind environments. This report documents:   Microclimates across eight car parks and reference sites covered by vegetation. Measurements of surface and air temperatures related to a range of car park surface materials. The cooling effect of shade in car parks. Current design guidelines and policies in Australia related to car parks. Alternative design solutions for cooler car parks. The empirical data and policy analysis are used to develop a set of recommendations for urban heat mitigation that can be applied to new and existing car parks. Because of the common nature of at-grade car parks around the world, the proposed cooling techniques can be applied globally, irrespective of the fact that the underlying case studies and data originated from Sydney

School Microclimates

Outdoor school environments need to be safe, stimulate physical and cognitive development of children and encourage learning. These key requirements are jeopardised by increasing summer heat. Summer heat limits outdoor activities and has adverse effects on physical wellbeing of school children and teachers. Children are particularly vulnerable to heat as they regulate their core temperature through convection, which becomes less effective when it is hot. Based on empirical data collections, this report provides more than 20 practical recommendations on how to reduce the impacts of outdoor heat. Although these recommendations were devised based on work around a public school in Western Sydney, their universal character allows applying them to any school or other urban build infrastructure. Avoiding the use of artificial grass in unshaded spaces, shading black asphalt, allowing natural air flows and using shade materials with highly reflective upper surfaces should be fundamental principles in design and building guidelines for heat-smart schools

Predicting resilience through the lens of competing adjustments to vegetation function

There is a pressing need to better understand ecosystem resilience to droughts and heatwaves. Eco-evolutionary optimization approaches have been proposed as means to build this understanding in land surface models and improve their predictive capability, but competing approaches are yet to be tested together. Here, we coupled approaches that optimize canopy gas exchange and leaf nitrogen investment, respectively, extending both approaches to account for hydraulic impairment. We assessed model predictions using observations from a native Eucalyptus woodland that experienced repeated droughts and heatwaves between 2013 and 2020, whilst exposed to an elevated [CO2] treatment. Our combined approaches improved predictions of transpiration and enhanced the simulated magnitude of the CO2 fertilization effect on gross primary productivity. The competing approaches also worked consistently along axes of change in soil moisture, leaf area, and [CO2]. Despite predictions of a significant percentage loss of hydraulic conductivity due to embolism (PLC) in 2013, 2014, 2016, and 2017 (99th percentile PLC > 45%), simulated hydraulic legacy effects were small and short-lived (2 months). Our analysis suggests that leaf shedding and/or suppressed foliage growth formed a strategy to mitigate drought risk. Accounting for foliage responses to water availability has the potential to improve model predictions of ecosystem resilience

Antioxidant responses to drought and heatwave as markers for climate stress and adaptation

© 2015 Dr. Agnieszka Wujeska-KlauseAccording to predictions, extreme events such as droughts and heatwaves will increase in frequency and intensity in the near future. Droughts and heatwaves can have negative effect on forests leading to dieback of more sensitive tree species with negative effect on ecosystem stability. The response of trees to stress conditions can vary between species or within one species, and such variation may depend on specific adaptations of trees to their preferred habitat. This study focuses on Australian trees from two common genera – Acacia and Eucalyptus, which have many species distributed across different habitats. Adaptation to various habitats of congeneric species provides a good model for studying responses of defence system to drought and heatwave stresses of ecologically different, but closely related species. Responses of the defence systems under stress conditions can help to understand which species will cope more efficiently under future climate change predictions. This thesis consists of one meta-analytical review on antioxidative and photoprotective defence system responses to drought stress, three experimental studies conducted under controlled conditions and one field study. In the controlled experiments, two Acacia and two Eucalyptus species adapted to contrasting habitats were exposed to drought stress or heatwaves conditions and to a combination of both stress factors. Response of seedlings to the treatments was examined with measurements of antioxidative defence systems, specifically two ubiquitous and abundant low-molecular weight antioxidants glutathione and ascorbic acid, along with gas-exchange, chlorophyll fluorescence and gene-expressions measurements. In the field study, responses of antioxidative defence systems were measured on multiple provenances within one species in a common garden experiment. Provenances were from different sites of origin representing a range of habitats with different annual rainfall. It was hypothesised that responses of antioxidative defence systems will depend on stress intensities, the stress factors in question, seasonal changes (for the field study) and on species adaptation to habitat conditions. In conclusion, antioxidative defence systems responded differently depending on stress intensities, different stress factors and adaptation to habitat conditions. Concentration of antioxidants increased in response to initial stages of stress, but more severe stress conditions led to decreased concentration of investigated antioxidants in conjunction with more oxidised redox states of those antioxidants. Antioxidants showed stronger response to heatwaves than to drought stress alone, and a more pronounced response to a combination of both stress factors than to each factor separately. Responses of antioxidative defence systems varied between closely genetically related trees species adapted to contrasting habitats. Tree species from arid or low – moderate rainfall habitats showed delayed stomatal closure, more efficient photoprotection and no or weak antioxidative defence system responses to stress conditions. In contrast, tree species from humid or high rainfall habitats closed stomata early, had less efficient photoprotection and stronger antioxidative defence systems responses. Antioxidant responses within the same species but different provenances were highly dependent on environmental conditions, and to some extent dependent on the provenance, but there was no clear relationship to environmental factors at the site of provenance origin