Over the centuries, countless cities have risen and fallen. So it makes sense to ask if a city like Sydney is viable in the long term. That's what I believe sustainability means - is it viable long term?
I think sustainability is a question all city leaders should be asking. Even if it wasn't clear that the climate was changing. So what makes a city viable in the long term?
Is it a great place to live? Is it a city that takes care of people from all backgrounds and attracts creative, tech and business talent?
Sydney won't be here long term unless it's sustained by a strong economy - we need jobs and we need investment. Does the city support businesses, especially the start up businesses of the future?
Can people get around? Decent public transport, for me, means roads for people who need to drive, safe cycleways for people who want to ride, good paths and signage for people walking, and an integrated, functioning public transport network.
Does it have a strong sense of community?
We live in a multi-cultural, high density residential area and many people living here race from apartment to office block. Do we have beautiful open spaces, parks and playgrounds, excellent pools, libraries and other community facilities, as well as the creative arts and events to keep them physically healthy and inspired?
Do we have a range of housing and is it affordable?
The fact is that in cities, thinking and planning for the long term - basically, sustainability - is just good governance.
When my independent team was elected to the City of Sydney council in 2004, I wanted to develop a long term plan for our city.
I strongly believe governments should consult widely, develop a plan and then get things done.
We ran unprecedented consultation with our city communities, businesses, visitors, academics, institutions and experts to create our long term Sustainable Sydney 2030 strategy.
The overwhelming response was that people wanted Sydney to tackle climate change, they wanted it to be a globally competitive and innovative city, with functioning transport and a far better environment for bike riding and walking.
And we're now putting it into practice.
Unlike New York or London, the State Government controls vital areas such as transport in Sydney - not the council. So our game plan has been to act where we can, and have the research and plans ready elsewhere and keep pushing the State Government for action.
It takes time. But it does eventually achieve results. Light rail is now on the State Government's radar and hopefully in the plan they will announce in September, thanks to our advocacy.
We would like to see the George Street light rail as the beginnings of a network, with links east to the hospital, sports grounds and university in Randwick, across to the inner west and linking south to Green Square.
Unfortunately we don't control the buses, trains or ferries. But we can and are building a bike network - bike riding has grown 82% in the past couple of years, faster than any other comparable city.
We're improving the footpaths and signage for pedestrians, with rain gardens to filter stormwater and street plantings like the hedging we've introduced along Cleveland Street.
We've invested in car-share programs - around 1% of our 40,000 car parking spaces are now assigned to car-share vehicles. A new, independent study found each car share space replaces the need for 12 other cars.
That's real, long term solutions to the issues our city faces.
And we're doing it with balanced budgets, no debts - and without selling off assets to pay for it.
Our council has embraced sustainability and it is quite simply what every good government should be doing.
This year, researchers have all but closed the case on human activity and our changing climate - it's happening and we've caused it.
We've committed to cutting our emissions 70% by 2030 (on 2006 levels).
If elected, our independent team will take the city off the coal-fired grid by creating low-carbon precincts with locally produced power from trigeneration.
We are rolling out energy efficient LED street and park lights throughout the city.
Every one of the city Council's properties will soon have solar panels, in what will be the country's largest building mounted solar installation.
We're also retrofitting our buildings to use less water and energy and we've developed a decentralised water master plan to replace a tenth of our mains water demand with recycled water.
With so much rain in the past few years, it's easy to forget what drought is like. We haven't, and we're planning for it.
At Sydney Park, we've finished the first stage of a major water recycling project to capture and treat 51 million litres of storm water a year from the surrounding streets.
That water's being used to maintain healthy water levels in the wetlands - later this year, we'll start a second stage to collect and treat 845 million litres from surrounding areas for use in the park and in nearby businesses.
It's now standard for us to install rainwater tanks - at childcare centres, community centres, parks and sport fields.
We set up the Sydney Better Buildings Partnership with the owners of 60% of the city's office space to help us cut 70% of carbon emissions by 2030.
We work closely with residents and small to medium businesses, running workshops to help them use less water and energy and reduce waste, setting up community gardens and working to build strong urban villages.
From setting up a new City Farm to supporting a little cafe on Abercrombie Street where you can take your bike and fix it up with tools and spare parts, we're looking at ways to get people involved.
Because we know that cities like Sydney are the biggest consumers of resources and cities like Sydney are the biggest polluters.
But what's comforting is that cities like Sydney can paradoxically be the most powerful agents of change.
We have these huge challenges and we're positioned to solve them. It takes getting out of your comfort zone, and that can be uncomfortable, to say the least.
I don't believe we have a choice here. But there's no bigger challenge to solve and I think that's really exciting.
Speech for 'Think Act Change - Sustainability: what does it actually mean?' (August 14, 2012 at 99 On York, Sydney)