Urban greening has never been so important for liveability and sustainability. Australian cities have expanded rapidly since the 1960s, driving widespread land clearing and habitat loss, and pushing the green belts surrounding metropolitan regions further and further away from city residents.
Our cities have become denser too, with a corresponding loss of backyards, quarter acre blocks and the trees that used to spread throughout private and public spaces.
People living in urban locations are especially vulnerable to the negative impacts of increased temperatures, resulting from climate change and urban heat island effects. Trees, shrubs and grasses can help to mitigate these effects.
From transforming neglected streetscapes, to choosing climate-ready tree species, here are five ways you can support greener and cooler urban environments.
Protect our urban forests
The relationship between urban green space and cooler urban temperatures has been well established, yet trees are disappearing across Australia’s cities.
Our research showed that 55 of 139 urban local government areas across Australia experienced significant reductions in tree-canopy cover between 2008 and 2016. In total, this amounted to a national loss in canopy equivalent to 1,586 sq. km, or an area larger than the City of Brisbane.
Local governments identified vandalism of public trees and more requests to remove trees than plant them as among their biggest challenges to preserve trees and expand planting.
The public realm of parks and street trees is certainly a significant contributor to urban vegetation. But it is the private realm that contributes the majority of vegetation in our cities. In fact, residential land accounts for almost half the urban tree canopy in Melbourne, Perth and Sydney.
As our cities become denser, traditional ‘house and garden’ suburbs are replaced by mixed-dwelling developments and hard surfaces. Residents can help to reverse this trend of suburban vegetation loss by contributing to a thriving urban forest. Planting a mix of trees and shrubs at home has a much greater cooling effect than grass.
Choose the right tree species
We know that trees play an important role in keeping our cities cool. However, our urban forests will themselves be vulnerable to rising temperatures.
We studied the vulnerability to climate change of trees planted in 29 councils across Australia. The study found that 24 per cent of all public trees in Australia’s cities, or more than one third of tree species, will be at risk from increased temperatures by 2070, in a ‘business-as-usual’ emissions scenario.
So, which species should we be planting today to protect our urban forest against future climates? We also considered 753 new species for the City of Melbourne and identified many that will be well suited to the city’s rising temperatures. These include Australian native species such as brush box and the coast banksia.
Transform under-utilised green spaces
As cities grow and sprawl, we need to look for every opportunity – and space – to green our urban environments. There is a growing trend for Australian suburbanites to plant a colourful palette of low-growing native plants along the nature strip (or street verge) in front of their home.
Our research is documenting the learnings about native verge gardening – which plants work, what animals use this habitat, and what the neighbours think – from the residents already engaged in the practice.
Local residents interviewed explained that their key motivations were around saving water and time on maintenance and improving the visual appeal of their nature strip. They were inspired to keep going by observing wildlife attracted to their gardening efforts.
We found that native bees visited the majority of verge gardens. Many residents also enjoyed increased social interactions, as their verge garden provided a friendly place for conversation and neighbourly interaction.
By carefully choosing a range of different native plants for your verge garden, something can always be flowering (including over summer) to provide food and habitat for native bees, birds, and other animals.
As well as supporting healthy ecosystems, indigenous plants tell stories about the cultural belonging of Aboriginal and Torres Strait Islander people and allow a portal into the rich cultural and ecological knowledges held by Indigenous communities.
The Indigenous plant use booklet aims to help people understand not only Aboriginal perspectives of plants, but also the wide-ranging benefits of planting indigenous plants.
Reap the psychological benefits of greener spaces
Urban nature plays an important role in the daily experience of people living in cities. To better understand these potential benefits, we combined data from 2.2 million tweets with maps of urban nature in the Melbourne CBD.
We analysed the sentiment expressed in tweets and noted people’s proximity to urban nature.
We assigned an overall sentiment score to each tweet by aggregating across the different emotions expressed. For example, text reflecting positive emotions such as joy and text reflecting negative emotions such as anger were aggregated to reflect the overall sentiment in a tweet.
We found that people in parks expressed more positive sentiments and fewer negative sentiments in general than people tweeting from built-up areas.
This summer, try to think beyond the park – there are lots of different forms of nature in our cities. Why not take a look at maps of green roofs in the city? Or check out where your local waterways are? You might find new and exciting places to explore.
Explore a cooler way to travel
Urban heat can vary greatly by location – the difference between standing under a tree or in the sun can be as much as 10°C. Current navigation apps such as Google Maps provide instructions that account for distance, but what about shade?
Our Shadeways app was designed for the City of Bendigo, Victoria, to show the coolest routes for walking or cycling. It integrates freely available satellite heat imagery and Google street view images.
The platform helps active travellers understand how a route can expose them to different temperatures and plan a greener path that allows individuals to stay outside longer.
The Clean Air and Urban Landscapes Hub, funded by the Australian Government’s National Environmental Science Program, began in 2015 as a new research consortium with a focus on practical research to improve urban environments in Australia. The new e-book, Cities for People and Nature, showcases the hub’s work following six years of research.
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