Sierra Club Promotes
"Black Hole of Calcutta" Densities,
Then Retreats

Version for Narrower Monitors and Printing

On 18 June 2001, the Sierra Club dispatched an email (Email from the Sierra Club). advertising its new "Environmental Impacts of Sprawl Calculator," which purported to provide visitors to its website information on the environmental implications of particular levels of housing density, petroleum prices and automobile fuel economy. The calculator compared the results for the visitors inquiry to a neighborhood developed at what the Sierra Club called an "Efficient Urban" density of 500 housing units per acre and to one housing unit per acre "urban sprawl" (the typical suburban lot is 0.25 to 0.33 acres). Sierra invited people to:
    Enter the average residential density of the community, your cars' fuel efficiency and the price for a gallon of gas, and the calculator does the rest. Two communities are included for comparison: denser Manhattan neighborhoods at 500 units/acre, and the lower end of sprawl at 1 unit/acre. Are you ready to play?
The 500 unit per acre density is 3.4 times the highest density census tracts in Manhattan and more than double the most dense wards of Mumbai (Bombay) and Kowloon (Hong Kong), which are generally considered to be the most dense communities in the world. But Mumbai achieves its high population density with comparatively few housing units per acre. According to Police Commissioner Shivanadan, 55 percent of Mumbai residents are homeless. Moreover, the Sierra Club 500 housing unit per acre standard is similar to the densities achieved in the notorious, poverty and disease stricken areas of Manhattan's Lower East Side early in the 20th century and seven times as dense as Calcutta, with its infamous "black hole" of density and poverty.

In response, Demographia principal Wendell Cox posted a satirical email to two mailing lists, based upon the ludicrousness of advocating such high densities (Email from Demographia).

Soon thereafter, Thoreau Institute economist Randal O'Toole posted an email taking the arguments somewhat further. Mr. O'Toole's post was converted into a Thoreau Institute Vanishing Automobile commentary, which is reprinted below.

Little more than 24 hours after the Cox and O'Toole postings, the Sierra Club had significantly changed the "Environmental Impacts of Sprawl Calculator," to exclude the 500 units per square mile column and to replace it with three columns with lower densities, the lowest of which is "efficient suburban," at 10 housing units to the acre. The Sierra Club original and revised density classficiations are compared in the table below.

Samples of before and after output from the "Environmental Impacts of Sprawl Calculator" are available in the following executable files (simply "click" on the file name>

Sierra Club 500 Housing Unit per Acre Standard (Before)

Sierra Club Lower Density Revision (After)

Sierra Club Classification Sierra Club @ 2001.06.18 Estimated Population per Square Mile Sierra Club @ 2001.06.20 Estimated Population per Square Mile Notes
Efficient Urban 500 Housing Units/Acre 777,000 No longer shown at this density NA More than double the densest ward in (Bombay) Mumbai (289,000) and Kowloon, densest areas in the world. Seven times as dense as Calcutta and 3.4 times the most dense 2000 census tract in Manhattan (230,000), nearly 12 times as dense as all of Manhattan, 32 times as dense as New York City, nearly 50 times as dense as the city of San Francisco and nearly 200 times as dense as the city of Portland, Oregon.
Dense Urban Not Listed NA 400 Housing Units/Acre 622,000 Still more than double the densest Mumbai and Kowloon wards, 2.7 times densest Manhattan census tract, nearly 10 times Manhattan, more than 25 times all of New York city, 39 times the city of San Francisco and more than 150 times the city of Portland.
Efficient Urban Redefined @2001.06.20 NA 100 Housing Units/Acre 155,000 More dense than central Mumbai and Kowloon, double the density of the city of Paris, 2.4 times as dense as Manhattan, 6.5 times as dense as New York City, 10 times as dense as the city of San Francisco and 40 times as dense as the city of Portland.
Suburban Efficient Not Listed NA 10 Housing Units/Acre 15,500 Approximately the density of the city of San Franciso, 50 percent more dense than the city of Toronto and four times as dense as the city of Portland.
Sprawl 1 Housing Unit/Acre 1,600 1 Housing Unit/Acre 1,600 40 percent less dense than the average American suburb.
US Population per square mile based upon 2000 census ratio of population to housing units (2.43)

19 June 2001

To the Urban-Policy E-mail Group:


To the Transport-Policy E-mail Group:

Tuesday, 19 June, 2001 16:44

To brighten your day...

Below is a link to the Sierra Club's new density calculator, purporting to compare the environmental impacts of whatever level of density you like to densities of 500 dwelling units per acre. At my preferred density (one dwelling unit per 10 acres), the computer tells us that the average annual per capita vehicle miles traveled would be 66,000 --- a pretty impressive figure, and double that of current record holder Houston. Sounds reasonable to me.

500 dwelling units per acre calculates to 320,000 units per square mile, and at the average household size, more than 800,000 people per square mile. The most dense wards of Mumbai (Bombay) and Hong Kong are well below this density, and the densest census tracts in Manhattan are barely one-fourth this number. This would be a most attractive world. At this density, all US residents could live in an area approximately the size of Portland. Even Portland does not propose such craziness.

This would, of course, create very difficult problems. With only one city, how could there, for example, be a National Football League, with teams in 25 or so cities? Even a World Football League would be problematic, because all 6 billion people could be contained in something like 20 cities the geographical size of Portland --- too few for a proper American football league (not to mention a proper Rugby Union league, soccer league or Australian Rules league). There are doubtless other consequences not even imagined yet. Hope an environmental impact statement will be required.

Finally, the Sierra Club calculator claims that 2.2 million acres of farm land are lost to developers every year (why do they need so much land, one must wonder why it is that developers just go around consuming land!). This is about 3,500 square miles annually, and more than double the best reasonable estimates and 70 percent above the 1970s record, when forced busing and a whole lot of other issues combined to create the greatest expansion of urbanization in US history. Sierra must be using the discredited and withdrawn National Resource Inventory numbers (Even the new ones are rather questionable, with the density of new development in West Virginia from 1992 to 1997 estimated at one per 18 acres. Some of us would argue that development of that density is not urban).

All in good fun.
Wendell Cox


Thoreau Institute

How dense is dense enough for smart growth? Smart-growth advocates in the Twin Cities (average density: 1,800 people per square mile) say the Twin Cities needs to be as dense as Portland (average density: 3,000 people per square mile).

Smart-growth advocates in Portland say that Portland needs to be as Los Angeles (average density: 5,600 per square mile). Smart-growth advocates in Los Angeles say that Los Angeles needs to be as dense as Chicago (average density: 12,000 people per square mile).

Smart-growth advocates in Chicago say Chicago should be as dense as San Francisco (average density: 16,000 people per square mile). Smart-growth advocates in San Francisco want the City to be even denser still. Where will it all end?

Fortunately for a puzzled nation, the Sierra Club has answered this question in a web page that calculates the "environmental impacts of density" ( You enter your preferred density in households per acre along with your idea of average automobile fuel efficiency (miles per gallon) and the price of gasoline. The Sierra Club then projects the environmental and social impacts of your density. For comparison, it includes the environmental and social impacts of the "efficient urban density" and a "sprawl density."

On June 19, the web site indicated that the efficient urban density is 500 households per acre. Since the U.S. has an average of 2.4 people per household, this represents 1,200 people per acre or 768,000 people per square mile. This indicates that Manhattan, at only 52,000 people per square mile, has a ways to go before it reaches smart-growth perfection.

Demographer Wendell Cox ( points out that this is denser that the densest parts of Mumbai (Bombay) and Hong Kong. In fact, Cox adds, at this density everyone in the United States could fit into an area a little larger than Portland, Oregon's urban-growth boundary.

Perhaps in response to Cox's comments, on June 20 the Sierra Club modified the web page to compare four different densities:

* "Dense urban," which is 400 households per acre or slightly less than the "efficient urban" of the day before;

* "Efficient urban," which is "only" 100 households per acre;

* "Efficient suburban," which is 10 households per acre; and * "Sprawl," which the Sierra Club defines as one household per acre. Of course, 400 housing units could fit on an acre in a twenty-story building, each story containing twenty apartments averaging a little over 2,000 square feet. Add four or five more stories for shops and offices and some underground parking and you have a nice dense city of twenty-five-story buildings. But few cities have large areas of twenty-five-story apartment/mixed-use buildings. Even in Manhattan, most residences are in four- to ten-story buildings.

But the so-called efficient density of as dense as 100 households per acre is scary enough. At that density, the population of the United States could fit in the Los Angeles urbanized area -- call it "Sierra Club City." The entire population of the world would fit into the state of Virginia.

The Sierra Club assumes that all or nearly all office and retail establishments would be mixed in with the residential areas. It calculates that the efficient density would provide 48 "shopping opportunities per acre," whatever that means, as opposed to just 0.65 opportunities per acre at sprawl densities.

To be fair, some additional land would be needed for factories, warehouses, and other industrial areas. But that would still leave most of the rest of the world for farms, parks, and wilderness, which of course is the Sierra Club's goal.

How much land would Sierra Club City save? At the present time, U.S. cities, towns, and other urbanized areas occupy about 109,000 square miles of land. Roughly a third of that is industrial. If Sierra Club City replaced the other two-thirds, that would allow the restoration of about 72,000 square miles of land to farms, forests, or nature preserves. That sounds like a lot, but it amounts to just 2 percent of the land area of the United States.

Of course, if Sierra Club City stacks industry in twenty-five-story buildings too, then up to 3 percent of the nation's land could revert from urban uses to open space. Whether saving 2 or 3 percent is worthwhile depends on the costs of high-density living.

Start with congestion. The Sierra Club says that people living in sprawl densities of one household per acre would drive more than 32,000 miles per year. But at the efficient densities, says the club, they would drive only 7,600 miles per year, less than a fourth as much. Of course, with 100 times as many people per square mile, that means that total driving would be nearly 24 times more per square mile in Sierra Club City than in sprawl.

Urban Americans drive an average of 40,000 miles per square mile of urbanized land each day. As the highest density urban area, Los Angeles also has the highest density of driving: 124,000 miles per square mile of land.

But residents in the Sierra Club's efficient city would drive 1.3 MILLION miles per day for each square mile of residential area. That's 33 times more than in the average urban area and 10 times more than in Los Angeles.

Curiously, no matter what the population density, the Sierra Club model dedicates 93 acres of land per square mile to roads and sidewalks. It is not clear whether this is included in household per acre densities or is in addition. Assuming that it is in addition, then it represents about 13 percent of the land area, which is about right for suburban areas but is far lower than the percentage of high-density urban areas that is devoted to streets.

Ninety-three acres divided into twelve-foot lanes with three-foot sidewalks represents about 50 lane-miles of roadway. To handle 1.3 million miles of vehicle travel per day, each lane-mile of road would have to carry 1,100 vehicles per hour, twenty-four hours a day, seven days a week. Non-freeway arterial lanes can handle just that number, while freeway lanes can handle twice this amount, and lesser streets (collectors and locals) do less.

Thus, Sierra Club City will be about as congested as Manhattan during rush hour -- only congestion in Sierra Club city will be 24/7. The Sierra Club's "dense urban" density of 400 households per acre, of course, will be even worse: The club predicts that people will drive more miles per lane mile than the best freeways can handle.

With this much traffic concentrated in a small area, Sierra Club City will be one of the most polluted cities in the history of humanity. The city will produce less pollution per capita than in a sprawling city, but it will be far more concentrated.

Typically, the Sierra Club model crudely assumes that pollution is directly proportional to fuel consumption. The web site asks you to enter the average fuel efficiency you imagine for your city and it calculates the pounds of hydrocarbons (volatile organic compounds), nitrogen oxides, particulates (PM10), and carbon dioxide that will be produced. The Sierra Club doesn't estimate carbon monoxide emissions, but autos tend to produce about ten times as much CO as hydrocarbons.

The Sierra Club presents pollution in terms of pounds emitted per household each year. For carbon dioxide, which is implicated with global warming, total emissions may be crucial. But for many of the other pollutants, the problem is not total emissions but the concentration of emissions. Concentrations of carbon monoxide and particulates, for example, pose extremely serious health risks, while low levels can be tolerated and ignored by most people.

Sierra Club City will produce extremely dangerous levels of these toxic pollutants. Based on the Sierra Club's numbers, automobiles in sprawl emit about 100 pounds of hydrocarbons, a half ton of carbon monoxide, and 680 tons of particulates per square mile per day. But Sierra Club City will produce 2,340 pounds of hydrocarbons, nearly 12 tons of carbon monoxide, and more than 16,000 tons of particulates per square mile per day.

Since the Sierra Club model assumes that emissions are proportional to fuel consumption, all pollutants will be twenty-four times as concentrated in Sierra Club City than in sprawl. But in fact, cars pollute more in stop-and-go traffic, and the extra congestion in Sierra Club City will make it even more polluted than the Sierra Club numbers indicate.

The Sierra Club model also claims that high densities will produce less water pollution. "When more than 20% of the watershed is paved over and developed," says the club, "water pollution skyrockets." But a suburban neighborhood of one household per acre will have much less than 20 percent of its area paved over, while an urban jungle of 100 households per acre will be nearly all paved over. Thus, we can expect the most pollution from the urban area.

The Sierra Club's model is optimistic about the effects of density on driving. The model assumes that, at any density, doubling density reduces per capita driving by 20 percent. This is about four times greater than can be observed by looking at U.S. urban areas. However, it is about the amount generated by studies that looked at driving habits of residents of individual neighborhoods of various densities.

The problem with such studies is that they usually fail to control for family size, income level, and other factors that influence driving. A disproportionate number of people in high-density areas are either poor or have no children. They either can't afford to drive or have decided they would prefer to use transit. But this doesn't mean that forcing a middle-class family of four to live in high densities will lead them to drive significantly less.

Even without this error, Sierra Club City -- a permanently congested and dangerously polluted area -- will be far less attractive to most Americans than sprawl. But smart-growth advocates will nevertheless press for increasing densities in virtually every U.S. city.

Monday, 18 June, 2001 15:48

Subject: Sierra Club Sprawl/Traffic news - unveils neighborhood consumption calculator

Perhaps you are contemplating moving to a new home and wonder how much water it will use, or how much concrete or land. Or how convenient it may be to shopping, or how many cars you'll need and how much you'll drive -- and pay for gas, and pollute. Or perhaps you just have an acquaintance whose household consumption habits you'd like to nose into.

If you were looking for a single variable that would best predict all these, to use as a guide on where to look for that home, what variable would you use? Social class (income) of the neighborhood, or maybe average family size? Or perhaps nearness to the metro center, or convenience of local shopping? Or density of the area, quality of public transit, or nearness to a freeway?

That one best variable would be the density of the area! That's perhaps obvious for predicting the amount of land used. And a little less so for the amount of concrete and water (lawns). But how does density predict nearby shopping? Or auto ownership and driving and auto pollution?

Surprisingly, or perhaps not surprisingly, yes. Density does it! Neighborhoods come in patterns, where all these vary in the same direction, in lockstep. Density is the best single descriptor of these patterns. Of course, an individual family can break the pattern, but the design of the neighborhood either facilitates efficient use of resources or puts up barriers. On its webpage, the Sierra Club has a calculator to help you estimate these impacts. And help you choose an efficient neighborhood, or find ways to make yours more efficient. Each variable is explained, along with how it varies with density.

Enter the average residential density of the community, your cars' fuel efficiency and the price for a gallon of gas, and the calculator does the rest. Two communities are included for comparison: denser Manhattan neighborhoods at 500 units/acre, and the lower end of sprawl at 1 unit/acre. Are you ready to play?

The calculator's predictions are based upon only one variable, density. If you knew more about the neighborhood, you could make even better predictions. For instance, if you knew the density, average household income and size, public transit service and pedestrian/bicycle friendliness of the neighborhood you could even better predict auto ownership and driving, and resulting gas cost and air pollution. The location efficiency study uses these variables for surprisingly accurate predictions, at least in the Chicago, LA and San Francisco metro areas where they've been specifically calibrated. This study by the Institute for Location Efficiency (Center for Neighborhood Technology, Natural Resources Defense Council and Surface Transportation Policy Project), used to develop the Location Efficient Mortgage(SM), is described at

And finally, you can play around with how much a Location Efficient Mortgage(SM) could save you in Chicago, LA and San Francisco neighborhoods at

Well, let's play!

John Holtzclaw
sprawl and transportation action --

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