This is my last post for the time being on Sustainable Cities Collective and I want to take the opportunity to explain how I have come to understand the great value that it has.

Regular readers will know that at least 70% of the world's 9-10 billion population are projected to be living in urban areas by the 2080s, according to the United Nations. By then we may well be a way down the road to a 4^oC warmed world according to the latest climate science.

What will life be like for urban citizens? Will it be great or appalling? Will it be dystopia or utopia? The answer may depend upon whether you or your descendants will be living in a city which has implemented many of the ideas already covered on this website.

Many people who are not aware of the kind of things our writers publish here may also be unaware that some cities today are already preparing for the many difficult challenges of tomorrow, independently of the often short-term policies of the national governments within whose borders they find themselves.

Some of them are able to set policies and network widely to improve lives for their citizens. Part of the reason is the opportunity presented by the huge amount of infrastructure either being built or renewed, which permits the mistakes of yesterday to be undone and the best practices of today to be installed.

Hundreds of cities have in place targets for 100% renewable energy or electricity and some have already achieved this.

A new standard to measure the sustainability of cities, Sustainable Development of Communities: Indicators for City Services and Quality of Life (ISO 37120) is being piloted by 30 cities, with a further 229 cities signed up to the programme. It is being developed as part of an integrated suite of standards for sustainable development in communities by the Global City Indicators Facility.

A new ISO standard around smart cities is also being developed. Other standards of relevance to urban areas include the Genuine Progress Indicator (GPI), BS 8904:2011, which provides guidance for community sustainable development, the European Union's sustainable towns and cities program, ecological footprint analysis leading to the declaration of One Planet Cities and Towns, and life cycle assessment, which is already standardised through a range of ISO documents.

Beyond this there are many other indicators and standards, for example for energy management on the small scale and the United Nations emerging Sustainable Development Goals, which will, reportedly, contain both hard and soft targets and a goal specifically about cities. There's also the New Urban Agenda building for Habitat III in 2016.

But this is just part of the picture.

All around the world many different projects and initiatives both top-down and bottom-up are evolving in urban areas as cities gain more confidence.

A plethora of pan-global organisations are feeding this process, including but not limited to: ICLEI, UNEP, The World Future Council, WRICities, C40 Cities, the Covenant of Mayors, The Global Parliament of Mayors, European Sustainable Cities Platform and the World Business Council for Sustainable Development.

To take just one of these, 6,000 European cities have signed up to the Covenant of Mayors, a voluntary commitment to go faster and further than EU climate targets. Their climate action plans call for, on average, a 28% cut in CO2 emissions by 2020, 8% more than the EU's 2020 target.

Sustainable urbanism is a big movement. If the world has to live within its means, cities must lead the way.

It is therefore not fanciful to imagine that cities of the future, at least some of them, can become as sustainable as they used to be when the world's population was much smaller.

They have the potential of becoming more closed systems. They can take steps to reduce their entropy and contribute toward the needed reduction in Earth's energy imbalance, which is now about +0.6 W m?2.

These positive social, economical, technological trends are occurring in part because certain conventional methods of energy production, mobility, food production etc. are arriving at thresholds or limits.

In other words, that they could produce much more power themselves, and much more of their own food, encourage plenty of walking and cycling to keep the population healthy and fit, and promote social welfare and justice to keep the population happy whatever the ages and abilities of its citizens.

Tendencies in the collaborative economy, closed loop resource management, vertical farming, big data, self-driving cars, smart cities and so on can, potentially at least, support this trend.

In the face of the overwhelming threats of resource scarcity and climate change, increasingly such trends will become seen as more and more necessary. The alternative is that the dystopic future we have seen in big budget Hollywood science fiction and disaster movies will come to pass.

The negative feedback loops of climate change are likely to be in full swing in at least certain parts of the world by 2050, and self-sustaining cities may be the only way for them to become more resilient and survive since existing systems are extremely vulnerable.

Of course no one can know what will actually happen in the future. If we do not manage to get proper agreement on limiting climate change, then the world may well be too hot and negative feedback loops have kicked in that will only permit limited financial resources to be used for reactive damage limitation rather than proactive building of resilience and sustainability.

But it won't be for want of trying, and for the efforts of members of the Sustainable Cities Collective.