This is not news to me. Still though, it's nice to have it continually reconfirmed that cities are the green way to live. We probably can't support billions of people sustainably no matter what we do. But, we can have more people with less impact if we live stacked on top of each other.

Cities: still greener than small villages

Similarly, we should do the same when flying.

United Airlines Exploring Viability Of Stacking Them Like Cordwood

BUT, a city isnt self sustainable..
IF' you add in that the farmers have to DRIVE from the city to Farm.
And the more people in 1 city, the Farther he will drive, and return good.
The roads required for the Farmer, his equipment, shipping goods...on and on and on..ANd you dont need to OVER produce on smaller lots of land, as you do for the city.

And the word efficiency...IS WRONG.
Its the idea that you can place a Market/mall in 1 area and have TONS of people come to it for Everything.
The old way still worked better..
Current way is 1 MALL/store location for 20 miles of area.
OLD idea was that Grocery stores would cover/locate about every 2-3 miles, and stores in NEED, would be in those areas also.  SPECIALTY stores could be 1 per town city.
Impact of having a LAWN??  thats easy.  Look at the impact of NOT being able to get rid of water on Streets/foundations and RUN OFF from cities because that CANT clean it as it RUNS threw the sewers..All the chemicals and pollution DRAGGED along with it.  THEn get 1 small hole in the street/pavement, and WATCH the water eat all the underlayment..HOLE to SINK HOLE.

Of course, a city on its own is not sustainable. We'd probably all agree with that. However, if you want to have the highest possible sustainable population, perhaps some statistically significant percentage of today's horrifically unsustainable population, you need cities. Face it, heating, cooling, transportation, and many other facets of daily human life are all optimized far better when people are living together rather than spread out.

Here in NYC, for one example, we produce one third of the CO2 per capita of the rest of the nation. And, we're included in that national average.

No. The impact of having a lawn must be compared to the positive impact of a forest. Lawns are incredibly thirsty.

http://www.epa.gov/watersense/pubs/outdoor.htm

Our Love Affair With Our Lawns Is Hurling the U.S. Toward Water Crisis

My idea of a lawn is whatever survives, grass and plants existing together in a blend, not the current idea of a monoculture. Adds to the beauty, and the flowers are good all year round. It gets cut like it is being grazed, and this keeps it in order and under control.

I know about the LAWN problem, but Im not a person that LIKES what we use FOR LAWNS..
Look up Buffalo grass, GREAT stuff.

The problem we have is Sources and RESOURCES..
BUSINESS likes for everyone to be in a LARGE group.  you can build 1 location and FEED/cloth/Charge for utilities in 1 location.
But look at problems with SINGLE location and DISTRIBUTED power sources.
Insted of building 1 DAM/coal plant/...
we build homes that CREATE power with WIND and solar power.

Germany, which is SMALL, creates over 23% of their power with solar/wind.  WE only create 3%.
Distributed power is VERY hard to control(by corps).
Its very hard to KNOCK IT OUT..if 1 power site goes down, a WHOLE STATE doesnt loose its power.
Corps want access to 1 location to MAKE money..even tho they have to run WIRES to every house on the block/city/town/farm.  They want the CONTROL.

http://www.pbs.org/independentlens/power-paths/
interesting story about Indian LAND and POwer companies DIGGING COAL off that land, then CLOSING plants.