Just How Green Is the New Green Cities Index?

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Part two of a two-part series on a recently announced set of sustainability rankings. Air quality, water, and more.

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Earlier this week I reviewed the overall, land use, and transportation components of the new "Green City Index," which rates and ranks 27 cities in the U.S. and Canada on various environmental criteria (and which is sponsored by Siemens). Today I consider the rest of the report.

As noted in the previous post, all ratings and rankings of places with respect to environmental issues are imperfect at best, for the reasons I stated. In this case, you certainly have to wonder about the methodology for a study that classifies Los Angeles among the leaders for air quality (more on that issue below). But such studies, though flawed, still can be useful as starting points for serious discussion about issues.

CO2, energy & buildings

These categories are (or should be) very closely related. Buildings, along with transport, provide a large majority of overall urban carbon emissions, so one would expect CO2 performance to correlate closely with building and transportation performance. In addition, since most of our energy consumption comes from the combustion of fossil fuels, CO2 performance should also correlate closely with energy performance.

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That is not what the results suggest, however. Vancouver is the only city to make the top five in all three categories. Otherwise, there was no overlap at all among the top five in CO2 and buildings. Los Angeles was the only city other than Vancouver to make the top five in both CO2 and energy, and San Francisco was the only city other than Vancouver to make the top five in both energy and buildings.

Here's a likely reason why: Although the CO2 scoring considered carbon emissions per unit of GDP and per person (both valid measures), the "energy" scoring looked only at electricity consumption as a quantitative measure, leaving out natural gas and vehicle fuels (both carbon emitters) among sources of energy. The quantitative "building" scoring, for its part, was based only on the number of LEED-certified buildings per capita. Given that certified buildings remain a small fraction of overall buildings in all cities, this was more an indication of policy or aspiration than of environmental performance. In addition, two-thirds of the "building" ratings were based on qualitative evaluations of policy measures. (Subjective policy evaluations composed a third of the scores for CO2 and energy.)

So I suggest taking some grains of salt, as they say, with these results:

  • CO2 top five: Vancouver, Miami, New York City, Los Angeles, Ottawa.
  • Energy top five: Denver, Boston, San Francisco, Vancouver, Los Angeles/Toronto (tie).
  • Buildings top five: Seattle, San Francisco, Washington, Pittsburgh, Vancouver.

I am very surprised to see Miami and Los Angeles in the top five for CO2, considering the amount of transportation emissions generated in each. The report doesn't explain L.A.'s high rating other than with respect to policy, but notes that its CO2 performance has improved further since 2002, when the study's comparative CO2 data were collected. Miami's good performance is attributed to a lack of industry in the city and reliance on newer, more efficient power plants than used by other cities.

Among global comparisons, the report states that the 22 U.S. cities in the study, on average, emit approximately twice as much CO2 per person as the five Canadian cities in the study, as well as over three times as much CO2 as European cities, and approximately four times as much as Asian cities studied in similar Siemens-sponsored research.

Water

This category measured water consumption per capita (important, but an order of magnitude more important in arid regions), "share of non-revenue water shortage leakages," and subjective evaluations with respect to policies to protect a city's "main water sources" and stormwater management. 

Maybe they were hampered by a lack of data sources, but this looks like a particularly weak evaluation to me. Wouldn't it be more relevant to measure drinking water purity or pollutant loads in city waterways? Wouldn't water consumption be more relevant if expressed in ratio to levels of precipitation?

  • Top five: Calgary, Boston, New York City, Minneapolis, San Francisco.
  • Bottom dwellers: Detroit, Montreal, Cleveland, Washington, Philadelphia.

New York's strong showing is attributed to very low water consumption per capita, which I suspect is related to far fewer lawns and gardens to irrigate per capita. (The report's authors relate it solely to policy.) Calgary scored well in all categories. Among the losers, I was curious about Philadelphia, given that the city is becoming an "industry leader" (along with Seattle) in the U.S. for green stormwater management. This gets a mention in the report but must not have counted for much; the biggest negative seems to be aging water infrastructure that generates a relatively high number of leaks.

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Kaid Benfield is the director of the Sustainable Communities and Smart Growth program at the Natural Resources Defense Council, co-founder of the LEED for Neighborhood Development rating system, and co-founder of Smart Growth America. More

Kaid Benfield is the director of the Sustainable Communities and Smart Growth program at the Natural Resources Defense Council, co-founder of the LEED for Neighborhood Development rating system, and co-founder of Smart Growth America. He is the author or co-author of Once There Were Greenfields (NRDC 1999), Solving Sprawl (Island Press 2001), Smart Growth In a Changing World (APA Planners Press 2007), and Green Community (APA Planners Press 2009). In 2009, Kaid was voted one of the "top urban thinkers" on Planetizen.com, and he was named one of "the most influential people in sustainable planning and development" in 2010 by the Partnership for Sustainable Communities. He blogs at NRDC's Switchboard.
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