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The science of urban greening

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Life past the tipping point in Western Sydney

For one day during the bushfires, Penrith, NSW was declared the hottest place on the planet. How can a rapidly growing suburb cope with a new reality of extreme heat?


After platypus hunting in Tasmania, reading treemail in Melbourne, and touring experimental subdivisions in southeast Victoria, I wasn't quite sure what to expect in the Western Sydney suburbs after the bushfires. But differences between New South Wales (NSW) and Victoria were immediately obvious.


I visit a lot of fellow researchers while on the road, and everywhere I went in NSW my colleagues were quick to point out the dying vegetation. Even in the heart of urban areas far away from the fires, landscape plants are scorched and canopies are dying back, presumably due to drought, extreme heat, or both.


Heat damage is common on Sydney area plane trees.

My local host Dr. Sebastian Pfautsch, a Senior Lecturer at Western Sydney University, is an expert on the extent and impacts of heat waves in this region. He introduced me to the city of Penrith, NSW which has been featured in news stories all over the world. On January 4, 2020 they reached an officially recorded air temperature of 48.9oC, which was the highest global temperature that day. Sebastian's own sensor network showed even higher local readings exceeding 51oC, or 124oF. Many communities in this region are not adapted for these kinds of weather events, which are becoming more frequent.


I was immediately curious about Penrith, which seems like a harbinger of issues to come in other cities around the world. How will communities cope when temperatures far exceed the range of a healthy, safe, and livable environment? As elsewhere, there are many residents of Penrith without access to air conditioning, and who rely on walking or public transport to commute. What kinds of solutions are available to help?


Signs of changes to come


In response to a crisis of skyrocketing temperature, Penrith took action in a way I didn't quite expect. They organized a "masterclass" on Cooling the City and invited decision-makers, developers, organizers, and residents to listen to the latest research, innovations, solutions, and paths forward for mitigating and adapting to climate change. You can read about it here. I spoke about the University of Utah Research Park Vision Plan, a living lab retrofit at our Salt Lake City science and technology park that's putting the principle of designing with nature into action. Then I had a chat with landscape architect Josh Byrne (who I later learned is an Australian TV celebrity!) about design solutions to heat and water limitations.


I also learned much more about the local context of nature-based as well as built environment and policy solutions to Australia's escalating crisis of extreme weather and climate. The Greater Sydney Commission and Resilient Sydney are producing nuanced and state-of-the-art responses to the challenges of building equitable, just, green, and livable cities. We heard from Eleni Myrivili from the City of Athens about new tools and policies internationally, and from Simon Toze at CSIRO about living lab projects around Australia.


The city of Penrith is solicting input on cooling strategies from a wide range of experts and professionals.

I also learned that the state of New South Wales has embarked on a 5 million tree planting initiative aimed at combating a number of urban and environmental problems. If you've read other posts on this blog you may have gathered that I'm not a huge fan of arbitrary planting targets, many of which are too high for local conditions based on what we learned from the previous generation of million tree planting programs. But in a fascinating panel discussion, Steve Hartley of the Department of Planning, Industry, and Environment spoke with panelists and audience members about planning and policy barriers to change at the state level, and the possibilities for embracing more nuanced and locally adapted policies and solutions.


Built environment solutions to extreme heat


In my last post I wrote about the limitations of using trees to combat the public health crisis caused by urban air pollution. When it comes to cooling, trees do have measurable impacts on temperature - particularly surface temperature and something called mean radiant temperature, which contributes to human comfort. The technical details about how trees, parks, and irrigated landscapes can and can't cool the environment will be the subject of upcoming posts.


For now, I want to note that as many cities, including Sydney, have learned, there's often limited space in dense urban areas for large shade trees. Even when the space is available, trees take decades to grow large canopies, so the largest cooling benefits of tree planting will not be felt right away.


In the meantime, there are immediate and effective options for cooling the urban environment right now. Sebastian has taken on a number of projects to document and advance these options. Like me, Sebastian was trained as a tree ecophysiologist but found himself interested in urban environmental and socioenvironmental problems. He deployed networks of temperature sensors around western Sydney suburbs to study the relationship between land cover and temperature.


These studies have found that black roofs and asphalt parking lots (Australian translation: bitumen car parks) are an enormous and arguably unnecessary source of urban heat. Sebastian recommends testing cool pavements and providing targeted shade in playgrounds and around schools. Because the impacts of cool pavement have been mixed, he's using weather stations and drones to monitor car parks before and after cool pavement resurfacing.


This drone is equipped with an infrared camera to monitor heat before and after car parks are treated with reflective surfaces for cooling.

In Melbourne, I observed major changes to water capture and infrastructure following the Millennium drought that seem to be making the city more resilient to future climate shocks. In the Sydney region, massive heat waves are a similar impetus for change. How far it will go is hard to say, but if consulting with experts, reviewing the latest evidence, collecting new data, and monitoring innovative experimental solutions are the first steps for effective and transformative change - as I believe they are - they are well on their way.


Many thanks to the Penrith City Council, their organized and helpful staff, and Mayor Ross Fowler OAM for allowing me to participate in the Cooling the City Masterclass.



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