We know that there's a strong correlation between urban density and energy efficiency. Communities packing 12 or more households per acre are more efficient than less-dense communities built with the latest Energy Star appliances and materials. When planned and executed well, high-density residential areas can be appealing even to those reluctant to give up the space of single-family-home suburbia. When high density is the result of lack of planning or poor decisions, however, the result can be bad -- very bad.
The article in Tuesday's Washington Post talking about urban density patterns has generated a bit of attention because of its seemingly counter-intuitive ranking (based on US Census data) of the Los Angeles metropolitan area as having the highest density of any urban region in the US. Indeed, this is surprising to those of us accustomed to thinking of density as meaning skyscrapers and closely-packed townhouses. But the story that leapt out at me from the numbers was just how close the San Francisco-Oakland metropolitan region was to LA in terms of density. Based on the 2000 census, Los Angeles has 7,068 people per square mile, while SF-Oakland has 7,004 people per square mile.
Flying into Los Angeles International Airport at night, it's easy to believe that density figure. There are points during the approach when, from thousands of feet in the sky, all an airplane passenger can see is a sea of lights stretching from horizon to horizon, hundreds of square miles of human occupation, stopped only by the Pacific Ocean to the west. From the ground, during the day, it doesn't have quite the same character (except perhaps when trying to drive the 405), due to the "polycephalic" character of the city. Los Angeles doesn't have a single center or downtown, it has dozens. San Francisco, conversely, has the trappings of the conventionally dense city: strong core, abundant pedestrian and mass transit traffic, mixed-use neighborhoods and residential streets with houses pushed (sometimes literally) right up against one another.
Los Angeles and San Francisco, neck-and-neck at #1 and #2 on the population per square mile list, represent two very different models for the urban density future -- and both versions face important challenges.
I've lived most of my life in one or the other of these two metropolitan regions, and feel very comfortable and at home in both. There are aspects of life in each that I find marvelously appealing; the diversity and abundance of culture and activity in LA, the street life and complexity of San Francisco. (Perhaps that's why I find London so attractive -- the sheer volume of Los Angeles coupled with the traditional core density of SF.) I offer this aside not to personalize this post so much as to ground my observations: these two locations are very much part of my world.
As the Post article discusses, the engine of the Los Angeles density model is "infill." Because Los Angeles cannot, for all intents and purposes, expand its geographic area, its relentlessly growing population settles interstitially, whether in quick developments on previously waste-strewn areas (such as Signal Hill, which required bioremediation efforts to make the land clean enough to build upon) or simply by packing more people per house. The latter is startlingly common phenomenon in the poorer, and largely Hispanic, parts of Los Angeles. Garages are converted into tiny homes; "single-family" houses come to hold two or even three families. More traditional high-density housing can't be built in volume, as there are few places left upon which to build, and tearing down homes to put up apartment and townhouse complexes simply removes residential space even as more people arrive.
But if the legendary Los Angeles sprawl transformed into a high-density setting, the infrastructure has not kept up. Roads, water and sewage systems, schools, parks and myriad day-to-day services are hard-pressed to provide for a population many times that expected by planners in the 1950s and 1960s. And trying to build new services faces the same unpleasant dilemma as trying to build more housing: construction of new schools or businesses (let alone parks) means tearing down inhabited homes. The Post notes that a single elementary school can require 200 houses be destroyed -- and given the residency patterns, this can mean far more than 200 families displaced. This helps to understand the greater traffic problems in the region -- if businesses can't be built near residential communities, the citizens will have to travel to the businesses to work.
This hyperdense sprawl clearly came as a surprise to planners, and Los Angeles was caught flat-footed in its response. There was no planning, just reaction, and often not even enough of that. And while Los Angeles is the first major region to see the infill density engine kick in, it won't be the last: any metropolitan region facing geographic limits to continued sprawl but continuing to see a population influx will start to see the dense sprawl that Los Angeles now experiences.
San Francisco-Oakland faces a different problem, albeit with a similar underlying cause. Like LA, the SF Bay Area region continues to see a net gain in population (SF lost population shortly after the dot com bubble popped, but has since started again to grow). Unlike Los Angeles, however, SF-Oakland doesn't have a significant lower-density sprawl in which to "infill," either with new construction or multiple families in one home. Instead, the continuing population demand without significant increase in supply means that housing prices in the area have skyrocketed. The median sale price of a single-family home in San Francisco stands at over $700,000 currently, up from just over $560,000 in 2003; Alameda County (in which Oakland is the biggest city) has a median price of $620,000.
Where is everyone going who is priced out of the SF market? The US Census statistics give one clue: outside of LA, SF and San Jose, the remaining three California cities in the urban density top ten -- Davis, Vallejo and Tracy -- are all distant "commuter" cities in the broader San Francisco region (each about 60 to 90 minutes away by car... if there's no traffic.) And infill is happening here too, with the suburban cities between SF/Oakland and these distant commuter centers seeing both rapid sprawl and increased prices. If the population of the SF region continues to grow -- and no planning is done -- eventually these distant low-density communities will start to see the "dense sprawl" effect hit, too.
If these are the two models for very-high-density urban environments, what can we do?
Both the LA infill density and the SF surreal estate density models beg for planning relief, but they ask very different planning questions.
One very interesting aspect of this dilemma is that many of the more obvious steps that would retrofit sprawl for density -- multi-family housing complexes, better mass transit, higher-efficiency systems for water and power -- are also those needed to make these communities more closely resemble the "bright green" urban ideal.
This question is not easy to answer, however, as the "more obvious steps" can also be among the more costly steps. This, in turn, has political implications. As useful as efficient mass transit may be when serious infill density hits, for example, the limited use it would see early on would make it unable to pay its own way, and lead to questions about the wisdom of the endeavor. Not many political figures would have the guts to hold on in such a situation.
Solutions here are, if anything, even more difficult than in the LA model. One possibility that comes to mind is the encouragement and development of traditional high-density centers in the peripheral area outside of the city. To an extent, this has happened with Oakland, and arguably was a trigger for the growth of San Jose; there are few if any other cities in the greater SF area that are growing in a traditional high-density model. (This concept has some relationship to the "Edge City" model proposed by Joel Garreau in his book of that name.)
Such a solution would be risky for the original core, however, as businesses and taxpayers may end up moving out of the city to the new location, as it presumably offers similar -- or better -- amenities at a lower price. While this has a positive effect on prospective residents (it decreases demand, and lowers prices), it can have a starkly negative effect on the ability of the core city to support the services its citizens demand. Cutting services and raising taxes would both further contribute to the flight.
So, what are the solutions? How can we build higher-density, more efficient, and still attractively livable cities without triggering either the LA "infill density" problem or the SF "hyperexpensive density" problem? Are there examples of high-density, high-efficiency, livable cities that have managed to avoid both fates?
If you live in a city that hasn't quite reached these heights of density, but is well on its way, what can your city do to avoid either the Los Angeles or the San Francisco model?
Can you turn a city into a Bright Green Urban Dream and break neither the bank nor the people?
