In late May, the Australian Government released the Infrastructure Australia Audit, which explores how the nation will cope with an expected population of 30.5 million by 2031.

The audit underscores the importance of making our cities work. Cities are expected to contribute $1.6 trillion to the economy by 2031 – a 90 per cent increase on their current input.

The audit also gives us a clear picture of the future we face if we don’t get serious about sustainability, with skyrocketing congestion costs, high emissions and rising inequality just the start.

Over the last year, the Green Building Council of Australia has brought together some of the nation’s ‘city builders’, along with industry leaders and policy makers, for a series of forums which tackle the big question: what makes a city great?

In Sydney, Lord Mayor Clover Moore is proud of the City of Sydney’s efforts to reduce carbon pollution through green retrofits, with vast reductions in energy usage achieved through the installation of solar arrays and efficient LED streetlights, and thousands of square metres of green walls and roof space that is improving air quality across the city.

“Great cities don’t come by accident,” Moore said. “They emerge through choices we make and the commitment we bring to ensuring they are sustainable, equitable, inclusive, stimulating and beautiful.”

In Melbourne, Lord Mayor Robert Doyle is leading an ambitious Urban Forest Strategy – a plan to increase urban canopy cover from 22 per cent to 40 per cent by 2040. Significant investment in street furniture and paving for footpaths and streets is also helping to enhance the pedestrian experience of Melbournians. Doyle argues that “making our city more sustainable is directly connected with our future prosperity.”

In Brisbane, Lord Mayor Graham Quirk is looking at centralisation.

“As our cities grow up and become more dense, we need to embrace opportunities for centralisation – cooling, water, waste, energy,” he explained. “Great cities must also prioritise all four modes of transport – public, pedestrian, cycling and cars – rather than prioritising one at the expense of all others.”

The federal member for Perth and former WA Minister for Planning and Infrastructure, Alannah MacTiernan, stressed that the design and quality of the buildings within our cities would dictate their future success.

“There is a balance we need to achieve between planning regulation and best practice development that will ensure our buildings, streets and open spaces make up a real community and not just a collection of separate assets,” she said.

Great work is being undertaken all over the country, yet all of the leaders highlighted the need for a truly holistic approach to sustainable development in our cities. They also emphasised the importance of creating community within our urban areas.

As federal member for Melbourne, Adam Bandt eloquently put it, “Great cities need to be designed by and for the people that actually live in them, not just by committees or ‘ministers on high’‎ far removed from the effects of what they do. There needs to be control over density and assurances that what actually gets built is appropriate; so that it benefits the many not just the few.”

His comment are reminder of the risks we face in our quest to make our cities both green and great.

The first is the risk of diminished or conditional access. How do we ensure that sustainable cities and their benefits don’t become the exclusive privilege of the wealthy?

Enhancing the efficiency of our existing residential developments, and encouraging people to think beyond the ‘quarter acre block’ is a good start. The City of Sydney’s Smart Green Apartments program and the City of Melbourne’s Smart Blocks initiative both aim to make existing residential buildings more cost-effective and efficient while minimising their environmental impacts.

Another risk for great green cities is our narrow focus of investment. The majority of our Green Star-rated buildings are within in the office sector. While nobody would argue that green offices are a bad thing, creating truly sustainable cities demands green buildings outside office hours. But this is changing; we now have more than 100 Green Star-rated university and school projects, 40 multi-unit residential developments and five community developments – some that will one day have their own postcodes and be home to many thousands of people.

A third risk is disconnected decision-making. We need more connected thinking and a consistent, collaborative approach to city development. The Green Building Council of Australia believes a Minister for Cities would ensure a more integrated approach to the planning and delivery of critical infrastructure for our economic powerhouses, and drive the reforms needed to connect policies and programs across all levels of government.

As our population grows, our nation is changing. We must accept this reality, and embrace the opportunities that bigger cities present. Doing nothing will cost more than the $53 billion annual congestion price tag outlined in the Infrastructure Australia Audit. Doing nothing will mean cities that are less liveable, less productive and less sustainable for all of us.

Our cities are more than a collection of buildings – they are the engine rooms of our nation’s productivity, prosperity and future potential. As Bandt said, “we don’t just build buildings, we create communities.”