Click the image above to go to the article in which Alex Steffens, of Worldchanging (and TED, and plenty of other deserved) fame gives a synopsis on how to ramp up urban greening most efficiently:

If we’re talking about transportation, the best thing a city can do is densify as quickly as it can. That needs to be said every time this issue comes up, because it’s the only universal strategy that works. That’s the best-documented finding in urban planning—that as density goes up, trip length goes down and transportation energy use goes down.

For anyone new to “greening” it can be startling to hear an expert insist on denser development patterns as a solution. For most people working on green/urban issues this does not come as a surprise, but it is precisely the point that bears repeating:

We’ve run out of time for incremental approaches. For carbon-neutral cities, there are things worth talking about in how our consumption patterns can change—sharing goods, etc.—but those are a fraction of the impacts of transportation and building energy use. If we need to choose priority actions, the most important things are to densify, provide transit, and green the buildings.