Targeted, Hyper-Dense Neighborhoods Can Reduce Emissions

Alex Steffen presents the idea that by focusing development into "hyperdense" communities you create a host of benefits that reduce climate change by reducing trips.
Full Story: Alex Steffen: The shareable future of cities



Hyperdensity is too much of a good thing

Firstly, Alex Steffen isn't saying anything radically new here - similar proposals have been made at various times by George Dantzig, Technocracy, Inc., the Venus Project, and many others.

Secondly, "hyperdensity" is not necessary to achieve a walkable and efficient urban environment. A population density of around 10,000 people per square mile is sufficient to support a full range of services within a square mile area, turning each square mile area into a walkable neighborhood. 10,000 people per square mile can be achieved in human-scaled apartment buildings that are 4-5 stories tall.

Hyperdensity makes things less efficient than a city of 4-5 story buildings because taller buildings are more expensive to build and maintain per square foot. There is also the problem of importing massive amounts of food for large hypercities. A medium-sized city in the range of a million people can supply itself with food using the land which surrounds the city. A city of 10 million people has to import food from elsewhere, driving up energy consumption. Locally grown food is going to become essential for the sustainability of cities in the future. The megacities in Asia are just as unsustainable as the sprawling suburbs of America.

So, density is good. Hyperdensity might be too much of a good thing. I also question the value of the term "hyperdensity" as a marketing tool.


Hyperdensity and Environment

And hyperdense development probably does more environmental damage than traditional urban densities. See Michael Mehaffy's article about this at

I summarize Mehaffy's main point down at the bottom of the comments. There is some interesting discussion in the comments.

Charles Siegel

Importing food

"A medium-sized city in the range of a million people can supply itself with food using the land which surrounds the city"

Is this really true? What if people in Cleveland, for example, wanted lettuce and strawberries and other wide varieties of fruits and vegetables? They can't grow that outside their city, correct? Unless everyone lives on a farm on good soil and climate, won't we always have to ship food somewhere?

The main point: the need for cities to be part of the solution

"Tent pole" hyperdensity is just one throw-away line in this ten minute talk. It was offered as one alternative for achieving needed density, perhaps to better balance cities with large tracts of single-family housing. The speaker does not suggest that hyperdensity is necessary for walkable neighborhoods. And he is certainly not recommending that entire cities be hyperdense, hence the use of the term "tent pole."

This talk focuses on the need to drastically rethink cities if we are to rise to the challenge of climate change. He argues that cities must be and can be restorative.

Steffens argues that increasing the density of cities is key to making cities part of the solution, a familiar idea to readers of Planetizen, but perhaps not widely understood outside the planning community. Density is correlated with lower ghg emissions. Density results in less driving and lower rates of car ownership which reduces ghg not only from driving cars but from manufacturing them. The greater ease of sharing due to proximity in denser environments results in a reduced need to buy stuff and another reduction of ghg associated with manufacturing. And, of course, density is also associated with less energy use by buildings.

In addition to density, Steffens advocates green buildings, passive construction, and smart infrastructure that enables rain water capture, water cleansing and reuse, sequestration of the carbon in "waste." He also mentions the need to connect cities to nature by providing habitat within them.

Not new ideas, but I'd argue he puts them together concisely and clearly.

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