That’s the message of a new study from researchers at UC Berkeley. The research, which analyzes spatial differences in household carbon footprints (HCF) was published in the journal Environmental Science and Technology (paywall).
Unsurprisingly, the study finds that suburban areas have, on average, HCFs that are up to twice as large as the national average, which the authors place at 48.5 tons of CO2 per household. In dense urban centers, these numbers can be half the national average. On the whole, principal cities account for just 30% of total carbon emissions, while suburban areas account for 50% of emissions, despite having less than half of the total population. The significantly higher level of HCF in suburban areas, which reach above 85 tons of CO2 in certain areas, has the effect of offsetting many of the efficiency gains made by living in dense urban cores.
As Christopher Jones, a co-author of the study, notes:
“Metropolitan areas look like carbon footprint hurricanes, with dark green, low-carbon urban cores surrounded by red, high-carbon suburbs,” said Christopher Jones, a doctoral student working with Kammen in the Energy and Resources Group. “Unfortunately, while the most populous metropolitan areas tend to have the lowest carbon footprint centers, they also tend to have the most extensive high-carbon footprint suburbs.”
I decided to take a look at the variation of HCFs within Northeast Ohio. As expected, Cleveland and Akron both fit the model of a “carbon footprint hurricane,” as described by Jones. As the study notes, carbon emissions already start from a higher baseline in the Midwest due to the region’s heavy reliance upon coal for electricity generation (fortunately, in 2012, coal generation fell to 67% [PDF] of Ohio’s electricity generation from 85% in 2008).
HCF numbers stretch from lows of 21.1 tons and 26.5 tons in downtown Akron and Cleveland, respectively (numbers which are 57% and 45% below the national average), to highs of 75.4 tons in Hudson (155% of the average) and an astonishing 85.6 tons in uber-wealthy Gates Mills (176% of the average).
The two factors that ultimately supercharge HCF levels in Northeast Ohio’s suburbs are two of the central features of our sprawl-based development model – transportation and housing. In my neighborhood on Cleveland’s near West side (44113), housing – which includes emissions from electricity use – accounts for approximately 13 tons of carbon annually, while transportation generates just 7 tons.
Compare those numbers to 44139, the zip code for Solon, which saw its population increase by 9.56% from 2000 to 2010. In Solon, the average household generates 21 tons of CO2 from transportation and roughly 23 tons from housing. Not to mention that the average HCF in the suburb is 95% higher than households in 44113.
As I’ve discussed before, sprawl has been at the heart of development throughout Northeast Ohio since at least the advent of the Interstate Highway System. Despite seeing its population grow by just 0.32% from 1948 to 2002, the amount of land developed in Cuyahoga County increased to 95% from just 26% during this period.
As the population continued to spread out, vehicle miles traveled climbed, while public transportation utilization decreased apace. Annual ridership on the Greater Cleveland Regional Transit Authority plummeted from a high of 129,691,743 riders in 1980 to 44,680,000 in 2010 – a decrease of two-thirds in just 30 years. As a result, transportation accounts for 28% of greenhouse gas emissions (PDF) in Northeast Ohio.
These data clearly suggest that a suburban lifestyle is one of the leading drivers of carbon emissions in the US. Consistent with the fact that climate change is a massive environmental justice issue, the individuals in Northeast Ohio who generate the majority of carbon pollution are the least likely to endure the effects of climate change. Instead, as I’ve noted before, it is the poor, the elderly and infirmed, and persons of color living in urban areas – where carbon emissions are lowest – who will bear the greatest burden.
Unfortunately, Jones and Kammen also conclude that increasing population density is not the solution to this challenge. They find that increasing population density 10-fold only reduces HCF by one-quarter. Accordingly, they conclude that there is “no evidence for net [greenhouse gas] benefits of population density in urban cores or suburbs when considering effects on entire metropolitan areas.”
Instead, the authors argue that we need to increase energy efficiency in suburban areas by retrofitting homes, increasing penetration of electric vehicles, and expanding renewable energy generation. This suggests that urbanization is not a silver bullet to climate change, which is an important lesson to keep in mind as we move towards a world in which roughly 70% of people live in urban areas by 2050. We cannot afford to see US-style suburbanization expand into the developing world, or we may eliminate any chance of avoiding catastrophic climate change.