How mass immigration makes our cities hotter

For years, the development industry and urban planners have called for Australia’s supposedly underutilised middle-ring suburbs to be bulldozed for apartments and townhouses in order to house the many millions of extra migrants projected to inundate our cities over coming decades:

This transformation into a dense urban form is to be most stark in Sydney, where the Urban Taskforce projects that only one quarter of dwellings will be detached houses in 2057, down significantly from 55% currently:

This transformation will also see reduced access to green space, according to Infrastructure Australia’s modelling, as Melbourne’s and Sydney’s populations balloon to a projected 7.3 million and 7.4 million people by 2046 (see last highlighted row below):

An issue conveniently ignored by these planning geniuses is that in addition to eroding all markers of liveability (see above), their urban infill utopia will also make our cities hotter, causing increased heat-related deaths.

With canopy coverage declining across almost every city, researchers last year sounded the alarm:

Australian cities are increasingly becoming concrete jungles as trees and canopy coverage disappear, according to experts who warn this is contributing to an urban “heat island” effect…

It has estimated this can create on-ground temperatures as high as 55 degrees in the sun.

Compounding the issue, a 2017 report by the group, titled Where Should All The Trees Go, found canopy coverage in urban areas had declined in almost every state and territory…

Yesterday, The ABC warned that urban infill will bake our cities under concrete:

It’s a familiar sight across many Australian suburbs.

Demand for housing has led to a rise in subdivisions, and a loss of yard space and the trees they contain.

Block sizes for new houses across Australian cities have plummeted by 22 per cent — to an average of 467 square metres — in the past 15 years, according to the Australian Bureau of Statistics.

In Melbourne alone, about 240,000 new lots — including houses and units — have been created since 2015 as a result of subdivision…

Gregory Moore, a senior research associate at the University of Melbourne, has been studying Australia’s declining urban canopies.

“In most Australian cities, the density of the canopy cover is diminishing at various rates,” Dr Moore said…

“Nearly all of the change is happening on privately-owned land … and most of it is the redevelopment of large blocks into smaller blocks or into townhouse developments.”

The trend is exacerbating an urban heat island effect, where hard surfaces like concrete and steel absorb and then release heat.

Trees and the shade they provide can help reduce the impact, but stripping away that canopy accelerates the effect.

It can make our cities 4–10 degrees Celsius hotter than surrounding rural areas, according to research from RMIT’s Sustainability and Urban planning program.

Associate professor Joe Hurley and his RMIT colleagues have mapped vegetation loss in a number of Australian cities.

They found several outer suburbs in Melbourne and Sydney were most vulnerable to the heat island effect.

“Areas like the western suburbs of Sydney and the western suburbs of Melbourne, where we see lower socio-demographic factors, we also see lower vegetation and higher susceptibility to heat,” Dr Hurley said…

Anoop Sud lives in Stanhope Gardens in Western Sydney, and has seen it rapidly develop over the past 11 years.

Having migrated to Australia from India, Mr Sud said he was used to overpopulated cities, but now felt “claustrophobic” because of the number of houses and people.

As his neighbourhood becomes more crowded, he is finding it harder to escape the extreme heat — in February last year, temperatures soared to 44.5C, and Mr Sud found it difficult to breathe.

Dr Tony Matthews – a senior lecturer in urban and environmental planning at Griffith University – has been at the forefront, explicitly warning that infill development is driving the heat-island problem:

“Heat stress actually causes more deaths in Australia than all of the other natural disasters combined”…

Middle-ring suburbs were more likely to be the leafy, cool retreats created by postwar architecture and planting…

“The real problem comes when we try and increase densities, which we have done in a suburban context through a quality called urban consolidation,” he said.

“And that has been taken up through most of the capital cities, all of the capital cities, in fact.

“It’s squeezing more floorspace out of less land, so that’s why we’re seeing so many apartments, so many townhouses, we’re also seeing a reduction in block sizes from maybe 700 metres or 650 metres to 400 metres.”

Squeezing more properties onto land means there is less room for parks, trees, or anything other than constructed buildings, he said.

The result is dense, urban fringe suburbs with little greenery and houses with no gardens, parks reduced in size as competition for tenancy grows…

“What I feel we have done with these suburbs is we have locked them into a pattern of heat stress, limited outdoor activity, limited use of the public realm, and all of the problems that come with that because they’re not green enough and in some cases they don’t have the potential to be any greener,” Dr Matthews said.

The infill utopia of jamming millions more people into the existing urban footprint will necessarily chew-up green space as backyards, trees and open space are removed to make way for additional dwellings. And this will necessarily exacerbate the ‘heat island’ effect afflicting our cities, in turn raising energy use (think air conditioners).

Clearly, maintaining green infrastructure in our major cities is not consistent with the projected explosion of their populations via mass immigration, along with planning rules that force increased population density.

The first best solution to this problem is to slash immigration back toward the historical average, thereby slowing the destruction of green space.

Sadly, the latest Intergenerational Report projects that Australia’s population will swell by 13.1 million people (~50%) over the next 40 years on the back of extreme immigration of 235,000 people a year. This is the equivalent of adding another Sydney, Melbourne and Brisbane to Australia’s existing population:

Stop treating symptoms and address the problem at its source.