Selecting Sustainability Indicators

By Dom Nozzi

In January 2005, a committee in my community evaluated the value of various “sustainability indicators,” which are measures of trends that show whether a community is advancing or declining with regard to various measures selected by the community to show how well it is doing.Upward Trend

For example, a sustainability indicator might be the amount of gasoline consumed on an annual basis, either for the entire community or per capita.

The committee reviewed all the relevant documents from various community organizations, officials, media, and other sources.

The committee then vetted the indicators, discussed them with regard to the instructions from the Indicators Committee, and then seven members ranked them.

The results were as follows:

#1 Rank: SOx/NOx and other priority air pollutants

My evaluation:

This indicator would be relatively difficult to obtain on a regular basis and air pollution measurements in this sort of community tells us very little, or tells us the wrong thing. For example, higher air pollution levels in a town center could very easily be an indicator of a healthy, sustainable community because it can quite plausibly be due to more people/cars being in the town center. And this increase in the number of people or cars is likely to be due to an increase in town center health, attractiveness, or both. Manhattan certainly has higher Sox/NOx levels than most town centers, but Manhattan is perhaps the greenest city, per capita, in America.

#2 Rank: Total CO2 equivalent emissions

My evaluation:

Again, this data would be extremely difficult to come by, particularly on a regular basis. And might give us incorrect impressions of community health or sustainability. I am certain, for example, that the most UN-sustainable, environmentally ruinous communities in America have (or could have) an impressive collection of LEED buildings (buildings that are highly rated for energy efficiency and other green measures associated with building design), homes using solar energy/water, an impressive tree canopy, etc. Have we achieved sustainability and environmental conservation and a healthy community if all our homes have solar water heaters, but thousands of such homes are in remote, utterly auto-dependent, sprawling suburbs that are served by 8-lane arterials? Hardly. Every single building/home in Los Angeles could be an EnergyStar/LEED building. Every home could be consuming “green” energy. Does this mean that LA is meaningfully healthy?

#5 Rank: Acres of parks & conservation, preservation lands

My evaluation:

The supply of park acreage is very difficult to employ usefully. For example, if urban parks are located on large arterial roads and cannot be reached by bicycle or foot, they will tend to be underused (because of poor accessibility), and therefore not correlated to a more physically fit community. In town centers, parks can contribute to an enormous existing problem: Most all American town centers – despite what he conventional wisdom tells us — has a huge excess of open space (mostly consisting of parking or roads or private yards). Much of this urban “open space” needs to be put to urban uses such as residential, retail or office. Indeed, Steve Belmont (Cities in Full) makes the crucial point that the most important indicator of a healthy city is that lands are being converted from less intense to more intense uses (parking converted to retail, for example). Too often, in-town parks have a deadening effect on a town center. Note that I strongly agree that greenbelt land that rings the perimeter of a community is a very important sign of sustainability and health. Again, would LA be noticeably more healthy and sustainable if it had a big increase in parks? Absolutely not.

#6 Rank: Water quality (TMDL)

My evaluation:

Again, it would be exceptionally difficult to obtain this data. And there are a number of transportation indicators that can proxy for this indicator.

#8 Rank: Total Municipal Solid Waste Disposed & Recycled

Would it matter if the residents of LA all recycled their beer and soda cans? Or is this just an exercise in finding a convenient way of easing our guilty consciences because our lifestyle is so overwhelmingly unsustainable?

#9 Rank: Stormwater runoff

My evaluation:

Very, very difficult to gather data for this. And what would our public policy response be if we saw a declining trend? Put a moratorium on increasing the amount of asphalt parking? Much as I’d love such a tactic, it is a non-starter in American communities. Other conventional tactics, such as requiring the construction of enormous storm basins are commonly counter-productive because they create more unwalkable, car-dependent places.

#10 Rank: Biodiversity

My evaluation:

Again, this would be very, very difficult to gather data for.

In sum, it is crucial that the following criteria be used to select useful indicators:

  1. Tracking. Is the data for the indicator available? And is it easily tracked over time? Is it available on an annual or otherwise regular basis? If not, the indicator is nearly useless.
  2. Relevance. Can the indicator be used to draw conclusions based on the adopted community goals and objectives? Can it be used to make policy decisions? If not, how would the information be used?
  3. Durability. Can the indicator be used for the foreseeable future? Will data for the indicator be available in the future? For example, some indicators, such as lead levels in the air, are interesting, but may not be useful as a future measure of air quality if lead is completely removed from gasoline in the future.
  4. Accuracy. Does the indicator have a measurement methodology that produces accurate data?
  5. Responsiveness. Is the indicator relatively sensitive to subtle changes over time? If not, important changes can occur without being shown by the indicator.
  6. Clarity. Is the indicator readily understandable by the general public? Does it allow for a single interpretation, or is it so ambiguous that several conflicting theories can be used to explain the data?

Given the above six measures of indicator quality, I would suggest the following indicators for a community:

  • Citywide and town center residential density. There is no measure that more effectively creates a sustainable, environmentally benign community, on a per capita basis, than higher density. And nothing more environmentally ruinous than a low-density city. Higher densities are the most effective way to increase transit use/bicycling/walking, improve physical health, increase the number and viability of small & locally-owned/neighborhood-based retailers, discourage sprawl, minimize per capita energy/water use, and minimize per capita air/water pollution. Most, if not all, of the proposed indicators are strongly and directly correlated to residential density.
  • Mileage of travel lanes per capita. An effective measure of community quality of life, potential for sprawl, potential for transportation choice, and degree of tax burden. There is a strong inverse relationship here to a healthy, sustainable community. Less mileage per capita means more health and sustainability.
  • Gasoline consumption per capita. A powerful indicator of car dependence and community sustainability. More per capita consumption indicates more pollution, lower quality of life, and less sustainability. A relatively easy—yet meaningful—indicator to gather data for.
  • Total number of town center parking spaces. Nothing degrades the walkable town center lifestyle and town center residential and retail viability more than excess (particularly free, surface) parking. Any net increase in the supply of town center parking puts another nail in the coffin of town center health. Currently, nearly all town centers in America have an enormous excess of town center parking spaces.  For a town center to be healthy, it must be compact, walkable, and cozy – which is delivered by relatively high density. Parking is perhaps the most effective way to minimize density and reduce walkability. Less town center parking is an indicator of a healthier, more sustainable town center.
  • Per capita motor vehicle registration. A powerful indicator of car dependence and community sustainability. More per capita motor vehicle registration indicates more pollution, lower quality of life, and less sustainability. A relatively easy—yet meaningful—indicator to gather data for.
  • Average speed of cars on major town center streets. Higher average speeds directly correlate to more sprawl, lower quality of life, less viability for town center residential and retail, and a less healthy town center.
  • Annual number of road diets. This is a very direct correlation to higher quality of life, community health, sustainability, retail and residential health, and minimizing sprawl and pollution. A larger number of diets indicates a positive trend.
  • Traffic congestion in the town center. For locations where the community seeks to promote more infill, residential density, or commercial health, the most effective tool available is a growth in vehicle congestion. Increased congestion is also a powerful disincentive to suburban sprawl. And an effective way to promote transportation choice.

In sum, without adding a number of transportation indicators I suggest above, the proposed indicators I evaluate above from the sustainability indicators committee are “feel good,” lip service measures that will have very little utility for the purposes of measuring health and sustainability, or guiding public policy.

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Filed under Energy, Environment, Sprawl, Suburbia, Transportation, Urban Design

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