Urban planners and researchers warn increasing housing density in Australian cities must not be at the expense of tree cover and its cooling benefits.
A pilot study done by a team from the University of Melbourne warned “treeless” outer suburbs were a risk to health and wellbeing ::::
One of the researchers, Dr Stephen Livesley said housing developers now often had a focus on maximising the number of housing blocks while achieving minimum plot size.
“We need to consider the types of residential landscapes we’re creating now and what we’re asking people to live in for the coming 20, 30, 40 years,” he told 891 ABC Adelaide.
The researchers, in part, considered the “human thermal comfort” of Melbourne and its suburbs.
“We have warm cities because of the amount of heat-absorbing material. Cross that with climate change and in a heatwave event we’re starting to see some large mortality events,” Dr Livesley said.
“Trees can play a large part in preventing some of that exposure to high temperatures.
“The outer suburbs seem to be somehow disadvantaged and that’s something that we need to know. The urban ‘heat island’ does not stop at the CBD, the urban ‘heat island’ goes right out into the suburbs as well.”
Research looked at ‘established’ outer suburbs
Dr Livesley said the pilot study was prompted by a perception many outer suburbs had fewer trees than elsewhere and researchers were keen to work out if that were true and what the health implications might be.
“[It seems] that as you go out of the city, the outer suburbs – which aren’t necessarily young, seem to be less shaded by tree cover,” he said.
“We made sure the suburbs we were looking at were not very young. The suburbs that we looked at were at least 25-30 years [old].”
Dr Livesley said access to nature was important for wellbeing.
“You’re talking about the mental health benefits, the sense of place. That was one of the alarming findings we had from this small study in Melbourne,” he said.
“Why should people in those outer suburbs have less tree cover and less chance to interact with nature and birds?
“Just driving home or walking through a suburb where there is vegetation is able to calm you down after a stressful day at work.”
The team also considered how many urban dwellers experienced the natural environment.
“Many people’s experience of nature is very much in an urban context, so if you’re able to bring some of the biodiversity into the city … it means people will appreciate more of what it’s like to live in Australia and have a little bit of the bush in their own ‘backyard’,” Dr Livesley said.
Buyers in new areas ‘demand landscaping’
The Tree Advisory Board in South Australia said Adelaide’s outer suburbs were not necessarily sparse with tree cover, as the Victorian study suggested of outer urban environments.
Kelvin Trimper, from the board, said buyers in new housing areas were generally well served despite smaller blocks.
“People who are buying demand [landscaping]. Everyone understands the importance of developing that landscape in terms of creating that sense of community,” he said.
“[It is] letting people get out of their houses, get away from their computers, TV screens, and mix and mingle in the streets and in the parks.
“Get a mid-30s day in Adelaide and [in tree-lined] suburbs you still see people walking around because they’ve got the shade, they’ve got the protection, they’ve got the cooling effect.
“A suburb without that tree cover is like a desert.”
Mr Trimper said the cliched view that “leafy suburbs” were more affluent no longer was the reality.
“We tend to associate the green, leafy suburbs with affluence but that’s not necessarily the case,” he said.
“I think there are new suburbs emerging, both north and south of the city, where there’s been excellent cooperation between developers and local government to get the early canopy established as quickly as possible.
“I think we’re breaking with that long tradition where we used to think that only the leafy suburbs were the affluent people. I don’t think that’s true any more.”
Trees take time to grow to provide shade
Mr Trimper said despite smaller housing blocks, developers generally gave high priority to creating green suburbs.
“I think the tree cover in outer areas is actually there [but] it takes time to establish,” he said.
“[It is vital] we select the right trees to go in the right locations, so that we maximise the amenity they create, the cooling effect they have.
“Some need to be deciduous to let light in [to houses] during the winter, particularly where there’s higher density and we need that sunshine in the winter to feel warm and they’ve got to provide dense shade in the summer so we get the cooling effect.”
He said planning regulations helped ensure outer suburbs had adequate parks, reserves and street plantings.
“In SA we have rules about how much open space we require in our developments,” he said.
“In our growth suburbs – Salisbury, Playford, Gawler, Noarlunga – we’ve got a pretty good planning regime in place which ensures that developers and local governments place landscaping at the top of the list.”
Mr Trimper cited the success of the Golden Grove housing development in Adelaide’s north-east.
“Golden Grove did increase housing density in the 1980s and 90s. Now if you look across Golden Grove you can hardly see a rooftop,” he said.
Rising water cost a new factor
The rising cost of water became a more significant factor in decisions about planting since severe drought years less than a decade ago.
“Trees need water to survive, [but] we went through a drought over a number of years,” he said.
“To expect people to water a street tree, there’s a lot of water that’s involved there to get the tree established. Once it’s established, provided the tree was selected appropriately [for the climate] it can look after itself, but those early years it needs nurturing.
“The northern suburbs councils have resolved this by having access to recycled water, particularly for their reserves.”
The Tree Advisory Board said nurseries provided excellent advice if people went there with information about such things as the size of the area they wished to shade, how close footings and fences were and whether they needed winter light into their property.
“Similarly we have a tool developed by the Botanic Gardens called the plant selector tool, which helps us all in looking at the range of options of tree types for a particular location,” Mr Trimper said.
The number of dwellings approved for construction has jumped in the latest official figures. The Bureau of Statistics estimates that more than 17,000 homes were approved in October, seasonally adjusted, an 11.4 per cent increase on the previous month.
That recovered the ground lost in September, when approvals fell around 11 per cent. Apartment approvals entirely drove the latest result, jumping by more than 31 per cent as house approvals fell marginally.
The Housing Industry Association is encouraged by the rise in the number of dwellings approved for construction. HIA senior economist Shane Garrett said approvals have been volatile lately, but there are still healthy signs for the sector :: Read the full article »»»»