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.




Read more:
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.




Read more:
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.




Read more:
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.




Read more:
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.

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Technique developed in Kenya offers a refined way to map tree cover



File 20170908 25859 9cthdc.jpg?ixlib=rb 1.1
Each year satellite images and maps show patterns linked to land use/cover change.
Flickr/NASA

Michael Marshall, World Agroforestry Centre (ICRAF)

Scientists at the World Agroforestry Centre in Nairobi, Kenya, recently pioneered a new approach which uses satellite images and maps to show patterns linked to land use and cover change on a yearly basis. Though the technique was developed in Kenya, it can be used regionally and potentially across the world.

“Land use and cover change” are terms used by scientists to define changes to the earth’s surface. This can be due to natural causes or because of the way in which land is put to use by people. Land use refers to what’s being done on it, for example mechanised farming, while land cover refers to what is physically on the land, for example what crops are being grown.

What’s important about the new approach is that the maps consist of an array of both physical and human geographic data to explain changes. It can also be used in combination with large-scale climate models, for example to understand how changes in vegetation in East Africa might be affecting climate in other regions of Africa.

In Kenya’s case, the system mapped changes in agriculture and natural vegetation with information from over a 30-year period. Using a series of aerial photographic surveys – which could be used to distinguish specific crops or natural vegetation – and freely-available spatial data such as rainfall, and population density, interpreters were able to classify Kenya’s land use and cover change. They were then able to construct maps of this change on a yearly basis without extensive and costly field visits typically used when mapping change.

Understanding land use and cover change is important because they both affect how land responds to the environment. Many of the changes are human-induced – for example the way that people use the land can lead to habitat loss, increase the stress of life that the land supports, affect greenhouse gas emissions and storage, modify runoff and ground water storage, or alter the climate.

Deforestation, perhaps the most well-known type of land use and cover change, comes about primarily from agriculture and logging. It has an impact on the world’s climate because trees store huge amounts of carbon that would otherwise be in the air trapping heat. The absence of trees therefore contributes to global warming.

Deforestation also affects people locally, particularly in the global south. Forests help regulate rainfall and water storage, and the help maintain a high level of biodiversity.

Much of the global north has seen an increase in tree cover in recent years. But much of the global south continues to show declines due to population growth, weak institutions and other social and ecological factors.

Mapping deforestation

To understand the drivers as well as the effects of deforestation, geographers use various tools that map the extent and density of tree cover. These include aerial photos, satellite images and other spatial data through time.

The World Agroforestry Centre’s approach takes this a number of steps further. It also uses demographic data, such as population density, which is often bypassed by scientists when mapping change.

The new approach suggests that physical drivers, like rainfall, may not be as important as previously thought.

Finally, the new technique provides a way forward for scientists interested in understanding what drives land use and cover change. It allows them to look at how this process interacts with processes like climate change over large areas and long periods of time.

From a scientific perspective, this helps us better to understand the environment and how humans may be modifying it. This in turn will help those designing land management strategies.

Kenyan case

Our research in Kenya shows that the most important predictor of land use and cover change was population density. Kenya is part of the East African Horn region. Like many other countries in Africa, its population is growing rapidly and is largely devoted to rain-fed subsistence agriculture and pastoralism.

Population growth occurred more rapidly in fertile areas, so the conversion of natural vegetation to agriculture was much higher. In less fertile areas, population growth was much slower, so the conversion was less.

Kenyan farmers and pastoralists are largely unable to acquire new land and are instead forced to intensify their practices on subdivided land.

We were able to detect that as the number of people per square kilometre increased, the amount of natural vegetation declined, because it was being replaced by farm or grazing land.

Climate predictors, such as rainfall and air temperature, were also correlated with the conversion of natural vegetation to agriculture, but less so compared to population density.

The ConversationAs seen in the Kenya case, the growing demand for food in Africa must be met with effective land tenure reform. By mapping changes in our environment continuously over long time periods, farmers and policymakers can understand underlying mechanisms and explore opportunities for reform.

Michael Marshall, Climate Change Scientist, World Agroforestry Centre (ICRAF)

This article was originally published on The Conversation. Read the original article.

NSW Road Trip 2010: Packing & Getting Ready


It is now the day prior to the NSW Road trip 2010. I have begun packing and getting ready for the journey that lies ahead. I don’t expect to be taking a lot of gear, as I won’t be doing a lot of cooking, washing, etc, on this trip.

I have learnt that it is important to not assume that you have everything you need and then find out the day before that you may not – I already knew this of course, but having recently moved, I no longer have everything that I once did. For example, I do not presently have a sleeping bag. I got rid of the last one because it was old and smelly, and I planned to buy another. But a lot has happened since mid 2007 when I packed to move – including a near fatal car accident that put my purchasing plans well and truly on hold, and they then slipped into the area of my mind that ‘forgets.’

So now I have no sleeping bag – but that isn’t too important as I don’t believe I really need one this time round. It is a road trip, with several cabin stops along the way and only caravan parks with powered sites for the rest. I will take a couple of blankets should I need them (which I don’t believe I will – it will be quite hot in the outback this time of year).

Of course it is not just the sleeping bag that is missing. I am also missing a fly cover for the tent, but thankfully I had two tents so I’m OK there. There are a number of other items missing also, but I don’t really need them this time round. Thankfully I have spotted all this now, which means I can plan to purchase what I need for future adventures, back pack camping, etc. I had of course planned to buy these items, but with the passing of time I forgot.

Anyhow, the packing is under way and I just hope I don’t forget something I wish I had packed when I am on the journey. I’m relatively sure I haven’t – which isn’t to say That I have forgotten something.

What I’d like to remember – and tomorrow I’ll know for sure if I have – is how I packed the car, so that everything was easily accessible. I was fairly well organised for this sort of thing when I was doing it fairly regularly several years ago – but it has been a while. Minimal gear wisely packed, without leaving anything necessary behind – that’s the key for this type of journey and vacation.

This will be the first time however, that I have a bag dedicated to my online activities – laptop, digital camera, web cam, flash drives, etc. I hope to keep an accurate and useful journal online at the kevinswilderness.com website, with photos, comments, route map, etc. So this is a ‘new’ bag that I need to organise in the overall scheme of things.

Anyhow, packing is now underway and coming to a conclusion. The journey will soon kick off.