Hi Ihsan, the discussion on the compact city vs the sprawl city have been on the urban planning agenda for the last 20 years or more. Classic text such as Newman and Kentworthy (1989) compared cities from 30 countries and found that the cities with more housing density and less area (compact) have a better perfomance on energy consumption. However, this comparison have been challenged because of the different ways that countries measure urban areas and also different density measures (gross, net, etc) see Rickwood and Trubka (2009). Also, compact cities with no good public transport systems create an additional problem of traffic congestion , therefore less effective transport system and more carbon emissions. Therefore, density is not the only indicator that we should measure for sustainability, but also public transport availability, building perfomance and user behavior.

Thank you raul , do not you think that the impact of compression is different in the cities of industrialized countries from the developing world.

I agree with Raul that it is too simplistic to associate city compactness with sustainability. More consideration should be devoted to the system of urban transportation, people's preferences, etc.

I will question your definitions. What do you see as urban sustainability? Once we have established that, then your question might be able to be answered.

the urban environment is composed of built and non built components. For these components, proper sustainability issues have to be addressed (social, economic, and environmental sustainability).

So, we can see cities compactness from these dimensions to create a convenient urban areas. The compact city should also addressed the livability aspects too. Therefore; considering the sustainability dimensions are critical while creating compact cities.

dear Douglas Nuttall

Do you want to define the term "urban sustainability"? It is true that design and urban planning terms are not firmly agreed, but urban sustainability is not too vague .

Dear Feng Frederic Deng

Many research has illustrated the relationship of urban sustainability with compression, but it does have one concept of compactness in Hong Kong and Canada.

I did a quick Wikipedia search of the term, and I note the contradictions between Biophilia and Compactness, and the seeming absence of recognition of the upstream and downstream sources and sinks an urban center relies on. So, yes, I'm asking you what you mean by Urban Sustainability.

I understand sustainability to be "The ability of a community to meet all of the need of all of it's citizens, using the resources and ecological services of the land/water it manages, and the skills of it's population, in perpetuity". Unless the management scale is vastly larger than the urban boundaries, it doesn't seem to be possible for an urban center by itself to be sustainable.

Perhaps your understanding of Urban Sustainability already encompasses the larger community, such that it includes the interchange between the rural and urban, so that the resources and ecological services of the rural, and the community services and industry of the urban, are each used to support the other, but all of it is one community in the context of planning and administration. In which case, Urban Sustainability would be th con-joined twin of Rural Sustainability. But in my take of the concept, I don't see that, and I'm seeking clarity.

thank you Mekonnen Abebe Anshebo

thank you Douglas Nuttall

Sustainability is essentially an environmental concept. Over the past three decades, its paradigm has shifted from a balance of economic, social and environmental considerations to concern for the environment First, Therefore, the concept of urban sustainability was comes later after the Sustainability ,Its must be aimed to achieve the sustainability.

I agree that Sustainability is often treated as an environmental concept, only because there are voices speaking up about culture, and social problems, and the economy, and the endangered Whazit has no loud voice. So the simplest place to start is often the ecosystem.

But then one would be able to argue that having no consumption per person, or no people, would be the best thing for Sustainability, which it patently is not.

Saying that it is 'essentially' an environmental concept is akin to saying child care is essentially wiping bums and noses. That is certainly part, but certainly not most of the whole.

If Urban Sustainability is to lead to better ecological results, then it would be exceedingly dependant on the ecology of the locale you are in. Maybe denser is better, to leave more land rural. Maybe sparsity is better, to allow more biophilia. Humans can adapt their cultures to dense and sparse, so that is of no matter. Denser leads to somewhat lower operational energy, but much higher embodied energy, and replacing ecological services with municipal services.

I can show, fairly simply, that technological development increases the quality of life of an affluent community insignificantly. I can also show that human development will increase the quality of life of an impoverished or affluent community nearly equally. Focussing strictly on technological development will lead to less development for the same investment of cash.

Unless your Urban Sustainability model considers both human development and technological development, and considers both the rural area that supports the urban, and the urban area that supports the rural, it's going to be insufficient. It will be an expensive way to do not very much.

thank you Douglas Nuttall

The roots of sustainability are social, the poor are more destructive to the environment than others, but the rich are more polluting than the result of large consumption. Urban sustainability may be a path to sustainability in general, but environmental capacity will not bear all of these billions of people if they enjoy welfare, so the ecosystem will collapse. there for the concept of sustainability has recently shifted to environmental considerations.

OK. So lets start with this, bounding ourselves to begin with in the environmental sphere. So, in your analysis, how do you consider the environmental impact? I know how to use the Ecological Footprint and Biocapacity of the biomes being managed by the community, and I know one could use Planetary Boundaries for the same purpose. Do you use a different metric? How do you set the upstream and downstream boundaries? How to you bring ecologic elements into design decisions? Does density have a purely ecological function (eg, less sprawl = more rural land available), or are there other reasons to modify density? There are more questions that would have to be answered before we get to a carte-blanche statement about urban density, but that's a pretty good start.

Thank you Douglas Nuttall for your interest and useful answers