The intentionally sustainable city?

I just saw an announcement for a symposium, in Portland in July, about the global trend of "eco-cities":

The debate about global climate change, increasing urbanisation and advances in technological innovation have given rise to a new, rapidly growing international phenomenon: eco-cities. This symposium aims to explore this new global phenomenon by discussing what we mean by ‘eco-cities’; why they have suddenly become so fashionable; whether they deliver on their promise to be more sustainable; and who decides where, when and how they are implemented. [more info]

I'm rather sad that I won't be able to go, because it clashes with our Triple Bottom Line Reporting workshop. More importantly, it got me thinking about just how new an idea it discusses; not just the label "eco-city", but the whole idea of deliberately planning urbanisation to be in some sense sustainable. I'm about to visit London, where I grew up, and it strikes me as a great example of a city where everything environmentally friendly (density, public transport, mixed-use streets, parks and tree cover, lack of a major highway through the middle) is the way it is for reasons other than planning for environmental benefit. There are green initiatives now, such as the congestion charge and the London Rivers Action Plan [PDF], but these are things that have been introduced within my lifetime.

It's not that the idea of sustainability is new. The old testament warns against wantonly cutting down trees, with a straightforward argument from self-interest, and we have a talk coming up about the Buddhist scriptures' angle on climate change. All that's new is seeing these ideas taken seriously in mainstream discourse—dare I say it, even becoming trendy—which is one of the reasons we're developing this blog. As cities around the world make unprecedented efforts to become sustainable, we all have a huge amount to learn from each others' experiences.

This trend is one of the things that gives me hope for the world.