Thousands of city trees have been lost to development, when we need them more than ever


Thami Croeser, RMIT University; Camilo Ordóñez, University of Melbourne, and Rodney van der Ree, University of Melbourne

Climate change is on everyone’s lips this summer. We’ve had bushfires, smoke haze, heatwaves, flooding, mass protests and a National Climate Emergency Summit, all within a few months. The search is on for solutions. Trees often feature prominently when talking about solutions, but our research shows trees are being lost to big developments – about 2,000 within a decade in inner Melbourne.

Big development isn’t the only challenge for urban tree cover. During the period covered by our newly published study, the inner city lost a further 8,000 street trees to a variety of causes – vandals, establishment failures of young trees, drought, smaller developments and vehicle damage.

Still, thanks to a program that plants 3,000 trees a year, canopy growth has kept just ahead of losses in the City of Melbourne.




Read more:
Our cities need more trees, but some commonly planted ones won’t survive climate change


Canopy cover is crucial for keeping urban areas liveable, shading our streets to help us cope with hot weather and to counter the powerful urban heat island effect. Trees can also be a flood-proofing tool.

Trees add beauty and character to our streets, and (so far) they’re not a political wedge issue in the ongoing culture war that is Australian climate policy. In short, they’re a very good idea, at just the right time.

Counting the trees lost to development

The thing is, this good idea happens in the midst of a construction boom. In Melbourne alone, this includes thousands of new dwellings and billions of dollars of new infrastructure. Many of the new buildings are very large – there’s a handy open database that shows these developments.

This map shows the scale of development under way in the inner city.
City of Melbourne

Next time you’re walking past a large construction site, look for empty tree pits – the square holes in footpaths where trees have been removed. Maybe you’ve already seen these and wondered what all the construction means for our trees. Well, now we know.

Our study puts a number on the impact of major development on city trees. In the City of Melbourne – that’s just the innermost suburbs and the CBD – major developments cost our streets about 2,000 trees from 2008-2017.

Using council databases and a mapping tool, we tracked removals of trees within ten metres of hundreds of major developments. We found much higher rates of tree removal around major development sites than in control sites that weren’t developed.

An example of our analysis, comparing tree losses around sites with major development (orange) to control sites (blue). Trees within 10m of major developments were much more likely to be removed.
https://doi.org/10.1016/j.scs.2020.102096

Even with the City of Melbourne’s robust tree-protection rules, trees can be removed or damaged due to site access needs, scaffolding, compacted soil, root conflicts with services access, and even the occasional poisoning.

The City of Melbourne invited artist Louise Lavarack to create a roadside memorial to a poisoned plane tree, which was then shrouded in gauze bandages.
Tony & Wayne/Flickr, CC BY-NC



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We’re investing heavily in urban greening, so how are our cities doing?


Tree protection limits losses

The silver lining in this story is that the city council’s tree-protection policy seems to be quite effective at saving our bigger trees. The vast majority of removals we saw were of trees with trunks less than 30cm thick. Only one in 20 of the trees lost was a large mature tree over 60cm thick.

This may partly reflect the fact that the council charges developers for not only tree replacement but also the dollar equivalent of lost amenity and ecological values. It gets very expensive to remove a large tree once you factor in all the valuable services it provides. When a tree is a metre thick, costs can exceed $100,000 – and that’s if there are no alternatives to removal.

The protection of bigger trees means Melbourne retained canopy fairly well, despite losing over 2,000 trees. Only 8% of city-wide canopy losses during our study period happened near major development sites. This modest loss is still serious, as removals are having more of an impact on future canopy growth than current cover.




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Lessons for our cities

While Melbourne-centric, there are lessons in this study for cities everywhere. Robust policies to protect and retain trees backed up by clear financial incentives are valuable, as even well-resourced councils with strong policy face an uphill battle when development gets intense.

Our findings highlight that retaining and establishing young trees is especially difficult. This is troubling given these are the trees that must deliver the canopy that will in future shelter the streets in which we live and work.




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Keeping the city cool isn’t just about tree cover – it calls for a commons-based climate response


Improved investments in how young trees are planted and how long we look after them can help. For example, in a promising local study, researchers showed that trees planted in a way that catches rainwater run-off from roads grow twice as fast, provided planting design avoids waterlogging.

Finally, in the context of rapid development, buildings themselves can play a positive role. Green roofs, green walls and rain gardens are just a few of the ways developments can help our cities deal with both heat and flooding.

There are plenty of precedents overseas. In Berlin, laws requiring building greening have resulted in 4 million square metres of green roof area – three times the area of Melbourne’s Hoddle Grid. In Singapore, developments must include vegetation with leaf area up to four times the development’s site area, using green roofs and walls. Tokyo has required green roofs on new buildings for nearly 20 years.

The solutions are out there, and urban greening is rising in profile. Recent commitments in Melbourne, Canberra and Adelaide are promising. Our study findings are a reminder that, even for the willing, we’ll have to take two steps forward, because there’s inevitably going to be one step back.




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For green cities to become mainstream, we need to learn from local success stories and scale up


The Conversation


Thami Croeser, Research Officer, Centre for Urban Research, RMIT University; Camilo Ordóñez, Research Fellow, School of Ecosystem and Forest Sciences, University of Melbourne, and Rodney van der Ree, Adjunct Associate Professor, School of BioSciences. National Technical Executive – Ecology, WSP Pty Ltd, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Biodiversity and our brains: how ecology and mental health go together in our cities


Zoe Myers, University of Western Australia

Mental health in our cities is an increasingly urgent issue. Rates of disorders such as anxiety and depression are high. Urban design and planning can promote mental health by refocusing on spaces we use in our everyday lives in light of what research tells us about the benefits of exposure to nature and biodiversity.

Mental health issues have many causes. However, the changing and unpredictable elements of our physical and sensory environments have a profound impact on risk, experiences and recovery.




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Physical activity is still the mainstay of urban planning efforts to enable healthy behaviours. Mental well-being is then a hoped-for byproduct of opportunities for exercise and social interaction.

Neuroscientific research and tools now allow us to examine more deeply some of the ways in which individuals experience spaces and natural elements. This knowledge can greatly add to, and shift, the priorities and direction of urban design and planning.

What do we mean by ‘nature’?

A large body of research has compellingly shown that “nature” in its many forms and contexts can have direct benefits on mental health. Unfortunately, the extent and diversity of natural habitats in our cities are decreasing rapidly.

Too often “nature” – by way of green space and “POS” (Public Open Space) – is still seen as something separate from other parts of our urban neighbourhoods. Regeneration efforts often focus on large green corridors. But even small patches of genuinely biodiverse nature can re-invite and sustain multitudes of plant and animal species, as urban ecologists have shown.




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The small patch of bush over your back fence might be key to a species’ survival


An urban orchard in Perth.
Zoe Myers

It has also been widely demonstrated that nature does not effect us in uniform or universal ways. Sometimes it can be confronting or dangerous. That is particularly true if nature is isolated or uninviting, or has unwritten rules around who should be there or what activities are appropriate.

These factors complicate the desire for a “nature pill” to treat urban ills.

We need to be far more specific about what “nature” we are talking about in design and planning to assist with mental health.




Read more:
Increasing tree cover may be like a ‘superfood’ for community mental health


Why does biodiversity matter?

The exponential accessibility and affordability of lab and mobile technologies, such as fMRI and EEG measuring brain activity, have vastly widened the scope of studies of mental health and nature. Researchers are able, for example, to analyse responses to images of urban streetscapes versus forests. They can also track people’s perceptions “on the move”.

Research shows us biodiverse nature has particular positive benefit for mental well-being. Multi-sensory elements such as bird or frog sounds or wildflower smells have well-documented beneficial effects on mental restoration, calm and creativity.

Other senses – such as our sense of ourselves in space, our balance and equilibrium and temperature – can also contribute to us feeling restored by nature.

Acknowledging the crucial role all these senses play shifts the focus of urban design and planning from visual aesthetics and functional activity to how we experience natural spaces. This is particularly important in ensuring we create places for people of all abilities, mobilities and neurodiversities.

Neuroscientific research also shows an “enriched” environment – one with multiple diverse elements of interest – can prompt movement and engagement. This helps keep our brains cognitively healthy, and us happier.




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Reducing stress at work is a walk in the park


Beyond brain imaging of experiences in nature, there is growing and compelling evidence that contact with diverse microbiomes in the soil and air has a profound effect on depression and anxiety. Increasing our interaction with natural elements through touch – literally getting dirt under our nails – is both psychologically therapeutic and neurologically nourishing.

We also have increasing evidence that air, noise and soil pollution increase risk of mental health disorders in cities.

What does this mean for urban neighbourhoods?

These converging illustrations suggest biodiverse urban nature is a priority for promoting mental health. Our job as designers and planners is therefore to multiply opportunities to interact with these areas in tangible ways.

A residential street in Perth.
Zoe Myers

The concept of “biophilia” isn’t new. But a focus on incidental and authentic biodiversity helps us apply this very broad, at times unwieldy and non-contextual, concept to the local environment. This grounds efforts in real-time, achievable interventions.

Using novel technologies and interdisciplinary research expands our understanding of the ways our environments affect our mental well-being. This knowledge challenges the standardised planning of nature spaces and monocultured plantings in our cities. Neuroscience can therefore support urban designers and planners in allowing for more flexibility and authenticity of nature in urban areas.

Neuroscientific evidence of our sensory encounters with biodiverse nature points us towards the ultimate win-win (-win) for ecology, mental health and cities.


Dr Zoe Myers is the author of Wildness and Wellbeing: Nature, Neuroscience, and Urban Designn (Palgrave Macmillan, 2020).The Conversation

Zoe Myers, Lecturer, Australian Urban Design Research Centre, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Now Australian cities are choking on smoke, will we finally talk about climate change?


Blanche Verlie, University of Sydney

I moved to Sydney less than five weeks ago and the city has been shrouded in smoke haze on and off since then. I joke this is my “Sydney hazing” but it’s only now – having worked on climate change for over a decade – that I’m suddenly feeling burnt out. This is not in any way to compare my experience to those who have lost their homes, communities and loved ones to the bushfires.

But the smoke cuts through Australia’s clouds of climate denial that pretend we are neither vulnerable nor responsible.




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We often refer to the “atmosphere” and “climate” of a particular space or community. We can be “on cloud nine”, “under the weather”, or “snowed under”. We know the weather affects people’s moods. My research, and that from a range of disciplines, is increasingly finding that human emotional, social and embodied experiences are intimately related to the weather and climate.

So, might people’s climate concern be changing now Sydney and Canberra have air quality on a par with Delhi?

Psychological smokescreens

Research is mixed on how extreme weather changes people’s perspectives on climate change. After severe storms and floods hit the UK in 2013 and 2014, scientists found those directly affected were more worried about climate change and supported climate change policies beyond direct, flood-related mitigation.

On the other hand, climate-change sceptics polled in the US in 2011 were more likely to recall the summer of 2010-11 as a normal one, despite record-breaking heatwaves across the northern hemisphere.

Some research has suggested climate change can prompt “information aversion”, where we actively or subconsciously avoid distressing facts and construct a safer, more comforting narrative.




Read more:
Air pollution may be affecting how happy you are


This tendency may be what drives such bracing platitudes as: “Australia is a sunburnt country”; “We’ve always had fires”; “Us Aussies are tough!”

A few face masks aside, the majority of us in Australia’s smoky cities have appeared to continue with business as usual: people just keep going to work. But I hope that, below this surface, the lingering taste of char at the back of our throats is sparking a change in the political atmosphere.

Igniting political change

No one should tell you how to feel about climate change, but I can tell you that you have a right to feel angry and sad. It is normal to feel overwhelmed – a word that once meant being literally inundated by water – in a world with rising seas and increasing floods.

Relatedly, droughts can leave us feeling drained. Awakening and sitting with these feelings is really important, but it’s also crucial not to dwell in despair.




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The rise of ‘eco-anxiety’: climate change affects our mental health, too


The social atmosphere is changing, of course: over the last year, around the world, we have seen millions of people take to the streets demanding stronger action on climate change. Our Aussie kids have been leaders in this regard.

Research and polling consistently find the majority of Australians are highly concerned about climate change and would back government policies to rapidly decarbonise the economy.

But research also tells us hardly anyone talks about their climate concern. For example, a recent study from Yale University found only 18% of Americans hear people they know talking about climate change once a month or more. It makes sense: climate change is scary and has become highly politicised, meaning it is hard to know where to start, what to say, or who to talk to.

While this is a coping mechanism to try to protect ourselves emotionally, these norms work to deny the significance of climate change, prevent useful personal and social introspection and stall community action.

So how do we create a change in the political climate? Those of us for whom a smoky city is our only tangible experience, so far, of climate change, need to step up and demand our government not only meet minimum international obligations, but become the renewable energy and climate policy leaders we could be. We also need to talk about climate change more: with our friends, families, peers and communities.




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Discussing the fires last week, one colleague mentioned she was fuming. This struck me as an empathetic echo of the smouldering state of our regional communities. My favourite sign from the school strikes has been “As oceans rise, so do we”. And now, I’d like to add, “As fires rage, so do we”.The Conversation

Blanche Verlie, Postdoctoral research fellow, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

No Australian city has a long-term vision for living sustainably. We can’t go on like this


Mike Berry, RMIT University and Ian Lowe, Griffith University

This article is part of a series on rebalancing the human–nature interactions that are central to the study and practice of ecological economics, which is the focus of the 2019 ANZSEE Conference in Melbourne later this month.


Australia was already one of the most urbanised nations by the end of the 19th century. Unlike European and North American countries, Australia’s pattern of settlement did not have a neat urban hierarchy. The gap between the large and small towns was huge.

These patterns have intensified in the decades since federation, especially after the second world war. International and internal migration trends have driven rapid growth in the big cities, especially Melbourne and Sydney. This has created major problems with providing adequate housing, infrastructure and services.

The fundamental issue is the reluctance of urban communities and their leaders to discuss what might be sustainable populations.




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If we want liveable cities in 2060 we’ll have to work together to transform urban systems


The folly of unlimited growth

No Australian city has a long-term vision showing how a future stabilised population might be supported with the essential resources of food, water and energy. No Australian city has faced up to the inevitable social tensions of increasing inequality between a well-served inner-urban elite and an increasingly under-resourced urban fringe.

Leaders in cities that have not grown as rapidly, such as Adelaide, lament their failure to grow like Sydney and Melbourne, despite all the associated problems. All implicitly believe unlimited growth is possible.

In reality, the expanding ecological footprints of the large cities have created unsustainable demands on land to support urban dwellers. And the wastes the cities produce are straining the capacity of the environment to handle these.




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What is ‘ecological economics’ and why do we need to talk about it?


Given the many unpriced flow-on effects from dense urban growth and market-led development, governments are struggling to deal with the undesirable consequences. Congestion and pollution threaten to overwhelm the many social and economic benefits of urban life.

The growth and concentration of populations are also driving chronic excess demand for appropriate housing. The result is serious affordability problems, which are adding to inequality across society and generations.




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In 1970, urban historian Hugh Stretton pointed to the role of Australia’s widespread owner occupation in offsetting the inequalities generated in labour markets and by inherited wealth. This is no longer the case.

The dominant neoliberal economic ideology has resulted in a retreat from providing public housing. Abandoning would-be home-owners to the market has produced a situation in which urban land and house ownership is reinforcing class-based inequalities. Home ownership is increasingly the preserve of the affluent and their children.

Housing-related inequality is also seen in the geography of our cities. Poorer households are priced out of locations with better access to good jobs, schools, transport, health care and other services.




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Our big cities are engines of inequality, so how do we fix that?


Failures of governance

Governments in Australia’s federation are poorly placed to respond adequately. Responsibilities and fiscal resources are divided, creating obstacles to effective planning and infrastructure provision.

The main factor driving urban population growth is an unprecedented rate of inward migration. The national government sets large migration targets as an easy way of creating economic growth. This leaves state governments with the impossible task of meeting the resulting demand for infrastructure.

Jane O’Sullivan has shown each extra urban citizen requires about A$250,000 of investment. The total sum is well beyond the capacity of state and local governments.

Arguments between federal and state governments are heavily politicised, especially when it comes to major transport investments. Even within single jurisdictions, complex demands and unexpected consequences prevent effective action. The waste recycling crisis is a prime example.

State governments must also deal with difficult trade-offs between, for example, allowing further development on the edges of cities or encouraging higher density in built-up areas. This often involves conflicts with local governments and communities, concerned to protect their ways of life.

Australian planners and governments have long tinkered with policies to encourage decentralisation to smaller cities. Despite these attempts, the dominant pattern of urbanisation with its seemingly intractable problems has hardened, a triumph of reality over rhetoric.




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What needs to change?

To get beyond the rhetoric and make our cities more sustainably liveable requires a much more deliberate and interventionist role for government. It also requires residents of our cities and suburbs to be willing to allow their governments to interrupt business as usual.

This, we know from experience, is a big ask. It will step on the toes of the property lobby and ordinary home owners. In some cases, for example, the short-term financial interests of property owners are leading local authorities to ignore scientific warnings about the impacts of climate change on coastal development.




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Major changes are also needed in how urban land is taxed and the proceeds invested. “Simple” reforms like replacing stamp duty on land transfer with a universal land tax, as the Henry Tax Review recommended, will take political courage that has been absent to date.

More complex policies like finding ways of diverting population growth to non-metropolitan regions will take careful thought and experimentation. This might include relocating government agencies to provincial cities. This has been tried sporadically in the past at the federal level and in states such as Victoria and New South Wales. However, such cases tend to be one-offs and do not reflect an overall strategic plan.

Future generations will inevitably be critical of the complete failure of current leaders to plan for sustainable development.The Conversation

Mike Berry, Emeritus Professor, RMIT University and Ian Lowe, Emeritus Professor, School of Science, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Global bank urges cities to invest in new infrastructure to adapt to climate change



Our cities need to adapt to cope with more extreme weather events and other impacts from climate change.
Flickr/Shaun Johnston, CC BY-NC-ND

Elisa Palazzo, UNSW

The impacts of climate change on weather, sea levels, food and water supplies should be seen as an investment opportunity for our cities, says global investment banking firm Goldman Sachs.

In a report out last month the bank says cities need to adapt to become more resilient to climate change and this could “drive one of the largest infrastructure build-outs in history”.

The bank says cities will be on the frontline of any need to adapt because they are home to more than half the world’s population and generate roughly 80% of global GDP.




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The state of the debate

The report comes at a time when scepticism and wait-and-see approaches are still permeating the debate on climate action globally. The discussion on reducing emissions is dogged by disagreement on targets and actions to be undertaken.

Report cover.
Goldman Sachs

On the contrary, less emphasis has been placed on adapting to global warming, the consequences of which will play out for decades to come even if we meet the goals of the Intergovernmental Panel on Climate Change (IPCC).

Goldman Sachs has already said it acknowledges the scientific consensus that climate change is a reality and human activities are responsible for increasing concentrations of greenhouse gases in Earth’s atmosphere.

Much global attention has focused so far on the need for climate change mitigation and the reduction of CO₂ emissions. But the bank’s latest report addresses the urban adaptation strategies that are urgently required:

Greater resilience will likely require extensive urban planning, with investments in coastal protections, climate-resilient construction, more robust infrastructure, upgraded water and waste-management systems, energy resilience and stronger communications and transportation systems.

It acknowledges mitigation measures are essential to reduce global temperature in the medium and long term. But it argues we need to act immediately to minimise the current and future effects of climate change in urban areas.

The question is, why would a bank endorse such a vision?

Banking on climate change

The bank’s report is a collection of data and analysis on climate change from well-known sources, such as the IPCC, and a detailed list of expected impacts on cities.

For example, higher temperatures, more frequent and intense storms, and rising sea levels could affect economic activity, damage infrastructure and harm vulnerable residents.

Does the report represent a last call to brace for impact? Or is a more nuanced and somehow optimistic view of the process emerging?

In reality, it’s not surprising this call is coming from an international financial institution such as Golden Sachs. This report needs be read in parallel with the environmental policy framework of the bank which is its “commitment to addressing critical environmental issues”.

The latest report identifies urban adaptation responses and initiatives as market solutions and financial opportunities. It clearly points out where investments should be addressed.

The directions outlined range over infrastructural initiatives to measures that require financial investment. Our cities need better coastal protection, more resilient buildings and open spaces, sustainable water and waste management, and upgraded transport systems.

A call for action

There is a positive takeaway emerging from the bank’s viewpoint which is a pragmatic call for action.

This could reinstate a more optimistic view of climate change. It could overcome the wait-and-see approach by moving the discussions beyond mitigation only.

And the report has the merit to outline some major challenges emerging from the need of financing a comprehensive urban adaptation.




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First, the need for innovative sources of financing and new ways to support climatic transition.

Secondly, the need to look at equity issues emerging from an adaptation process. For example, should a city strengthen flood defences in the CBD or should it upgrade public housing in flood-prone areas? Given the scale of the aims we need to evaluate carefully where best to invest the limited resources available.

But in this respect, no solutions are proposed.

This report is one of the many financial reports on climate change we have seen recently, about the risks and opportunities for the banking and insurance system. It’s probably the first to acknowledge clearly the need for comprehensive adaptation investments to make our cities more resilient.

But in concentrating on the infrastructure needs for cities, the report seems to miss the big picture.

There is still a need to understand how more integrated actions will include the social and environmental dimensions of adapting to climate change to create more sustainable and equitable cities.The Conversation

Elisa Palazzo, Senior Lecturer, Faculty of Built Environment, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Keeping the city cool isn’t just about tree cover – it calls for a commons-based climate response



Where’s the shade? Trees are not an immediate or whole answer to keeping cool.
Cameron Tonkinwise, Author provided

Abby Mellick Lopes, Western Sydney University and Cameron Tonkinwise, University of Technology Sydney

This story is part of Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.


A recent report by the Greater Sydney Commission singles out urban heat as one of four priority areas given our coming climate. It identifies tree canopy as the top response for reducing city temperatures and delivering amenity. However, the public conversation about urban heat often misses the complex relationship between trees, people and the built environment, which challenges this response.

In soon-to-be-published research supported by the Landcom University Roundtable we found that responding to a more extreme climate requires new social practices and new relationships with the commons. Commons are the spaces, resources and knowledge shared by a community, who are, ideally, involved in the regeneration and care of those commons. Trees are an important social commons, but they also present multiple challenges.




Read more:
Our cities need more trees, but some commonly planted ones won’t survive climate change


Closing our doors to the great outdoors

For one, trees are an outdoor amenity, but we are spending more and more time indoors. For those who can afford it, air conditioning delivers cooling in the privacy of your own home or car – no need for trees.

However, staying in cool bedrooms and car rides mean less time outdoors and with others, which isn’t ideal for human health and well-being.




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Increasing tree cover may be like a ‘superfood’ for community mental health


Air conditioning also uses more fossil-fuel-based energy, which generates more greenhouse gas emissions. The result is more climate change.

Mixed feelings about trees

As the Greater Sydney Commission report makes clear, tree canopy in Greater Sydney is roughly proportional to household wealth. The “leafy suburbs” are the wealthier ones. This means tree planting is an important investment in less wealthy parts of the city, which experience more extreme heat days.

Number of days over 35°C recorded in various parts of Greater Sydney (July 2018-June 2019).
© State of NSW through the Greater Sydney Commission



Read more:
In a heatwave, the leafy suburbs are even more advantaged


However, research also shows people have mixed feelings about trees. In comparison to the neat shrubbery and easily maintained sunny plazas we’ve become used to in our cities, trees can be “messy” and “unpredictable”. Leaf litter can be slippery and natives like eucalypts, with their pendulous leaves, provide limited shade. People worry about large trees falling over or dropping branches.

Trees are often at the centre of disputes between neighbours. They can also be perceived as a security problem – if trees reduce visibility they might provide cover for wrongdoers.

In addition, insurance companies can charge a premium if a property is deemed at risk of damage by large trees. As we experience more extreme weather, laws on vegetation clearing are becoming more risk-averse.




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If planners understand it’s cool to green cities, what’s stopping them?


What trees where and when?

Urban development tends to give priority to roads and delivering the maximum number of dwellings on sites. This leaves little space for trees, which need to fit into crowded footpaths with ever-changing infrastructures. For example, will larger trees interfere with 5G?

When juggling priorities in the streetscape, trees often lose out.




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Trees versus light rail: we need to rethink skewed urban planning values


It’s an obvious point, but trees take time to grow. It can take many years for a planted sapling to become a shade tree. In that time there will be no shelter from the heat.

Also in that growing period, which can sometimes be unpredictable, trees need to be nurtured, especially in times of drought. And, once the tree is mature, fingers crossed that extreme weather events do not undo all those years of waiting.

So, while increasing tree canopy sounds like an obvious solution, trees are in fact a complex social challenge. In our research, we point to ways some of these tree-related tensions can be managed.

Shade in the meantime

A structure to support fast-growing vines has been built on one of Darwin’s hottest streets, but even these will take some time to grow.
Darwin We Love It/Facebook

Shade is an important civic resource. Large, mature trees with spreading canopy provide the best shade, so strategic construction bans and tree preservation orders are an obvious first step.

However, if shady canopy is decades off, we need to think about other, creative ways to provide shade in the meantime to ensure, for example, that people of diverse abilities can walk their city in reasonable comfort. This might include temporary shade structures such as awnings, bus shelters and fast-growing vine-trellised walkways (if there is space to create troughs for soil and the structure doesn’t cause access problems).

And, as the Cancer Council consistently reminds us, we all need to adopt more climate-defensive clothing.




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Requiem or renewal? This is how a tropical city like Darwin can regain its cool


An important alternative is to follow our regional neighbours and start to populate parks and other public spaces at night. This suggests a need for removable shade, so we can take part in activities like stargazing.

Cultivating an intergenerational commons

Mature trees can die back or die altogether, so other trees should be maturing to take their place. Usually, experts design and maintain landscapes for others to enjoy.

However, users of the cooling services of parks could be invited into the process of planning and realising landscape designs. This would give them a say on the trees of which they have “shared custody”. Planting for succession can create an intergenerational sense of ownership over a shared place.

Current planning practices tend to ignore wind and solar patterns. The result is urban forms that make heat worse by prioritising comfortable private interior spaces over the commons of public space. Designing cool cities means using trees, water and buildings to create cool corridors that work with cooling breezes – or even summon these in still, heat-trapping basins like Western Sydney.




Read more:
How people can best make the transition to cool future cities


These few examples point to new ways of living with trees as social commons, but they also point to new forms of commoning – collaborative forms of care and governance that invite people to adopt new social practices better suited to living well in the coming climate.

It is a positive step that state development agencies like Landcom aim to demonstrate global standards of liveability, resilience, inclusion, affordability and environmental quality. In so doing, they initiate transitions to these more commons-based ways of living.


In addition to the authors of this article, the Cooling the Commons research team includes: Professor Katherine Gibson, Dr Louise Crabtree, Dr Stephen Healy and Dr Emma Power from the Institute for Culture and Society (ICS) at Western Sydney University (WSU), and Emeritus Professor Helen Armstrong from Queensland University of Technology (QUT).The Conversation

Abby Mellick Lopes, Senior Lecturer in Design, Western Sydney University and Cameron Tonkinwise, Professor, School of Design, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Urban growth, heat islands, humidity, climate change: the costs multiply in tropical cities



During a heatwave in late 2018, Cairns temperatures topped 35°C nine days in a row and sensors at some points in the CBD recorded 45°C.

Taha Chaiechi, James Cook University and Silvia Tavares, James Cook University

Some 60% of the planet’s expected urban area by 2030 is yet to be built. This forecast highlights how rapidly the world’s people are becoming urban. Cities now occupy about 2% of the world’s land area, but are home to about 55% of the world’s people and generate more than 70% of global GDP, plus the associated greenhouse gas emissions.

So what does this mean for people who live in the tropical zones, where 40% of the world’s population lives? On current trends, this figure will rise to 50% by 2050. With tropical economies growing some 20% faster than the rest of the world, the result is a swift expansion of tropical cities.

Population and number of cities of the world, by size class, 1990, 2018 and 2030.
World Urbanization Prospects 2018, United Nations DESA Population Division, CC BY



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The populations of these growing tropical cities already experience high temperatures made worse by high humidity. This means they are highly vulnerable to extreme heat events as a result of climate change.

For example, extremely hot weather overwhelmed Cairns last summer. By December 3 2018, the city had recorded temperatures above 35°C nine days in a row. Four consecutive days were above 40°C.

Cairns’ heatwave summer.
Authors, using BOM temperature data

For our research, temperature and humidity sensors were strategically placed in the Cairns CBD to represent people’s experience of weather at street level. These recorded temperatures consistently higher than the Bureau of Meteorology (BoM) recordings, reaching 45°C at some points.

Highest temperatures recorded by James Cook University weather data sensors during the November-December 2018 heatwave in Cairns.
Image: Bronson Philippa, Author provided

Local effects magnify heatwave impacts

Urban environments in general are hotter than non-urbanised surroundings that are covered by vegetation. The trapping of heat in cities, known as the urban heat island effect, has impacts on human health, animal life, social events, tourism, water availability and business performance.

The urban heat island effect intensifies the impacts of increasing heatwaves on cities as a result of climate change.

Projections of increased heatwave frequency for Cairns region using visualisation platform on Queensland Future Climate Dashboard.
Queensland Future Climate Dashboard/Queensland Government, CC BY

But it is important to remember that other local factors also influence these impacts. These include the scale, shape, materials, composition and growth of the built environment in a particular location and its surrounding areas.

The differences between the BoM data recorded at Cairns airport and the inner-city recordings show the impacts of urban expansion patterns, built form and choice of materials in tropical cities.

The linear layout of Cairns has, on one hand, enabled the formation of attractive places for commercial activities. As these activity centres evolve into focal points of urban life, they in turn influence all sorts of socioeconomic parameters.

On the other hand, the form the built environment takes changes the patterns of wind, sun and shade. These changes alter the urban microclimate by trapping heat and slowing or channelling air movements.

The layout and structures of Cairns CBD alter local microclimates by trapping heat and altering air flows.
State of Queensland 2019, CC BY



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Shifting the focus to the tropics

To date, a large body of research has explored the undesired consequences of climate change and urban heat islands. However, the focus has been on capital and metropolitan cities with humid continental climates. Not many studies have looked at the economic and social impacts in the tropical context, where hot and humid conditions create extra heat stress.

Add the combined effects of climate change and urban heat islands and what are the socio-economic consequences of heatwaves in a tropical city like Cairns? We see that climate change adds another dimension to the relationship between cities, economic growth and development.

This presents a huge opportunity to start thinking about building cities that are not superficially greenwashed, but which instead tackle pressing issues such as climate variability and create sustainable business and social destinations.




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In cold climates, heatwaves and urban heat islands are not necessarily undesired, but their negative impacts are more obvious and harmful in warmer climates. And these harmful impacts of heatwaves on our economy, environment and society are on the rise.

We have scientific evidence of the increasing length, frequency and intensity of heatwaves. The number of record hot days in Australia has doubled in the past five decades.

Projections of changes in heatwave frequency for northern Queensland in 2030 and 2070.
Queensland Future Climate Dashboard/Queensland Government, CC BY

What are the costs of heatwaves?

Increased exposure to heatwaves amplifies the adverse economic impacts on industries that are reliant on the health of their outdoor workers. This is in addition to the extreme heat-related fatalities and health-care costs of heatwave-related medical emergencies. As a PwC report to the Commonwealth on extreme heat events stated:

Heatwaves kill more Australians than any other natural disaster. They have received far less public attention than cyclones, floods or bushfires — they are private, silent deaths, which only hit the media when morgues reach capacity or infrastructure fails.

Heat also has direct impacts on economic production. A 2010 study found a 1°C increase resulted in a 2.4% reduction in non-agricultural production and a 0.1% reduction in agricultural production in 28 Caribbean-basin countries. Another study in 2012 found an 8% weekly loss of production when the temperature exceeded 32°C for six days in a row.

The 2017 Farm performance and climate report by the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) states:

The recent changes in climate have had a significant negative effect on the productivity of Australian cropping farms, particularly in southwestern Australia and southeastern Australia.

Average climate effect on productivity of cropping farms in southwestern and southeastern Australia since 2000–01 (relative to average conditions from 1914–15 to 2014–15).
Farm performance and climate, ABARES, CC BY

It’s not just farming that is vulnerable. A Victorian government report report this year estimated an extreme heatwave event costs the state’s construction sector A$103 million. The impact of heatwaves on the city of Melbourne’s economy is estimated at A$52.9 million a year on average.

Impacts of heatwaves on Victoria’s main economic sectors.
State of Victoria Department of Environment, Land, Water and Planning, CC BY

According to this report, economic costs increase exponentially as the severity of heatwaves increases. This has obvious implications for cities in tropical regions.

As the next step in our research, we are examining the relationship between local urban features, urban heat islands, the resulting city temperatures and their direct and indirect (spillover) effects on local and regional economic activities.




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Making a global agenda work locally for healthy, sustainable living in tropical Australia


The Conversation


Taha Chaiechi, Senior Lecturer, James Cook University and Silvia Tavares, Lecturer in Urban Design, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.