Here's how Australia's cities have grown over the last 30 years

More than any other Australian city, Melbourne has led a 30-year turnaround in inner-city density (red indicates increases and blue decreases in density as persons per square kilometre). Image: author provided.

Since settlement, Australian cities have been shaped and reshaped by history, infrastructure, natural landscapes and – importantly – policy.

So, have our cities changed much in the last 30 years? Have consolidation policies had any effect? Have we contained sprawl? Yes, probably and maybe, according to our newly published research.

Reviving the centre

The great Australian baby boomer dream of home ownership caused our cities to spread out during the second half of the 20th century. Urban fringes expanded with affordable land releases, large residential blocks and cheap private transport.

By the 1980s, across Australia’s cities, the urban fringes were ever-expanding. Inner areas had become sparsely populated “doughnut cities”.

By the end of that decade urban researchers, planners, geographers and economists began to warn of looming environmental, social and housing affordability problems due to unrestrained sprawling growth.


Governments responded swiftly, focusing policy attention on urban consolidation through programs such as Greenstreet and Building Better Cities. Concerned individuals formed groups such as Smart Growth and New Urbanism to promote inner-city development and increased urban density.

Since this time, large- and small-scale policy interventions have attempted to repopulate the inner- and middle-urban areas. The common policy goal has been to encourage more compact, less sprawling cities. Subdivision, dual occupancy, infill development, smaller block sizes, inner-city apartments and the repurposing of non-residential buildings have all been used.

Mapping the changes

In a newly published paper, we map the changing shape of Australia’s five largest mainland cities (Sydney, Melbourne, Brisbane, Perth, Adelaide) from 1981 to 2011.

Across each of these cities, which together are home to 60 per cent of Australians, there has been substantial, suburbanisation and re-urbanisation. In the last 20 years this has resulted in a repopulation of inner cities.

In Melbourne’s case, the return to the inner city has been particularly pronounced in the last decade. Here, the population jumped from around 3,000 to 4,000 people per km². The extent of this change is visualised in the chart below.

Melbourne may well be the exemplar for inner-city rebirth. More than any other Australian city it demonstrates the 30-year turnaround from inner-city decline to densification.

Between 1981 and 1991 Melbourne became a classic “doughnut city”: population declining in inner areas, density increasing in the middle-ring suburbs, and growth steady in the outer suburbs. For example, in the inner 5km ring there was a decrease during this time of almost 200 people per km².

From 1991 to 2001, even though growth was still focused on the middle and outer areas, the inner area began to be repopulated. Overall, between 1981 and 2011 there were approximately 1,500 more people per square kilometre living in the inner 5km ring.

Over the last decade, greenfield development, infill and urban regeneration have increased urban density throughout Melbourne – as shown in the five-yearly map animation below.

Changes in Melbourne population density (persons/km² over the 30 years to 2011: red is increasing, blue is decreasing). Image: author provided.

While the turnarounds in Sydney, Brisbane, Adelaide and Perth have been less marked than in Melbourne, they are all no longer “doughnut cities”. This means that where people live in these cities has changed.

Australia’s cities are now more densely populated – and we are much more likely to live in inner areas than we were 30 years ago.

A result of government policy?

We can probably attribute the changes in where urban Australians live to government consolidation policies.

The policy focus throughout the late 1980s and early 1990s was based on incentives to repopulate inner and middle areas.

Policies were changed from 2000 to increase population density across whole metropolitan areas. State and territory strategic plans aimed to promote urban consolidation, with a focus on the inner city.

State and territory plans now focus much more on specific zones throughout the whole of the city, including former industrial areas and surplus government land. New housing development occurs within these defined zones, particularly around transport and areas with urban-renewal potential.

South Australia’s 30-Year Plan for Greater Adelaide targets growth in “current urban lands”, along major transport corridors and hubs. Similarly, the Plan Melbourne – Metropolitan Planning Strategy plans to establish the “20-minute neighbourhood”, contain new housing within existing urban boundaries, and focus development in new urban renewal precincts.

The map visualisations reinforce the scale of this absolute growth across each of the five major Australian cities over the last 30 years.

Have we contained sprawl?

Our research would suggest urban-consolidation policies have slowed but not prevented sprawl, especially in the faster-growing cities like Melbourne, Brisbane, Perth and Sydney.

So, have we reached the point at which our cities are full? How can we accommodate future population growth? And do we need to focus our attention on new urban areas?

Containing and, more importantly, controlling sprawl may present the next big challenge.

Neil Coffee is a senior research fellow in health geography at the University of South AustraliaEmma Baker is associate professor at the School of Architecture and Built Environment, and Jarrod Lange a senior research consultant (GIS) in the Hugo Centre for Migration and Population Research, at the University of Adelaide.

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

Two of the graphics in this article were updated to clarify that population density changes were shown in persons per square kilometre, consistent with the measure used in the text.The Conversation

 
 
 
 

How bad is the air pollution on the average subway network?

The New York Subway. Image: Getty.

Four more major Indian cities will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building its 14th subway line, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line after waiting for almost 100 years for it to arrive.

In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than 120m people commute by them every day. We count around 4.8m riders per day in London, 5.3m in Paris, 6.8m in Tokyo, 9.7m in Moscow and 10m in Beijing.

Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, half of the world’s population is now urban. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.

Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO2), produced in part by industrial emissions and road traffic, are responsible for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.

But what is the air like that we breathe underground, on the rail platforms and inside trains?

Mixed air quality

Over the last decade, several pioneering studies have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.

Subway, Tokyo, 2016. Image: Mildiou/Flickr/creative commons.

For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in Barcelona, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in Hong Kong, Mexico City, Istanbul and Santiago de Chile.

Of wheels and brakes

Such differences have been attributed to different wheel materials and braking mechanisms, as well as to variations in ventilation and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.

Second Avenue Subway in the making, New York, 2013. Image: MTA Capital Construction/Rehema Trimiew/Wikimedia Commons.

Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.

In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.


To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. New York subway workers have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the Stockholm subway system.

But a note of caution is struck by the observations of scholars who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.

The dominantly ferrous particles are mixed with particles from a range of other sources, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.

Comparing platforms

The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of IMPROVE LIFE project with additional support from the AXA Research Fund.

It reveals substantial variations in particle-matter concentrations. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of air-conditioning has been shown to produce lower particle-matter concentrations inside carriages.

In trains where it is possible to open the windows, such as in Athens, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at high speed.

According to their construction material, you may breath different kind of particles on various platforms worldwide. Image: London Tube/Wikimedia Commons.

Monitoring stations

Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the Barcelona subway system, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.

To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.

The ConversationSuch research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.

Fulvio Amato is a tenured scientist at the Spanish National Research CouncilTeresa Moreno is a tenured scientist at the Institute of Environmental Assessment and Water Research (IDAEA), Spanish Scientific Research Council CSIC.

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