How Urbanism Slows Global Warming
Sure, hybrid cars and other energy-efficient vehicles are part of the solution to global warming and oil dependency, but how much people drive is as important as what people drive.
The separate-use zoning codes that shape sprawling exurban areas make it impossible to do anything but drive between all important destinations -- home, work, school, stores and cultural destinations. Compact urbanism brings many of those locations within walking distance and urban densities support high-quality transit service, giving people convenient lower-impact ways of getting around. Even better, New Urbanism makes these features part of environments recognized for their livability, desirability and sense of place. It's not about taking away people's right to drive; it's about them choosing to use their cars less by taking advantage of compelling urban places.
The LEED-ND Public Health Report compiles convincing evidence on urbanism's role in reducing greenhouse gas emissions from a series of leading studies. I'll provide highlights from that report (and other sources) in a future posting, but in the meantime, CNU has just posted a concise slide presentation on the relationship between climate change and transportation (and the role of urbanism as a remedy) from Hank Dittmar, the co-author of one of those leading studies.
The slide above (from Dittmar's slideshow) shows how dense cities are commonly viewed as areas of concentrated CO2 emissions (when emissions are viewed on a per-square-mile basis) but are actually extremely low producers of such emissions when viewed on a per capita (or per household) basis. Specifically, the average exurban household in a sprawling Chicago exurb generates about 11.5 tons of C02 per year, but those in suburban areas served by commuter rail generate 23% less C02 with their cars, or about 9 tons on average. By moving to a city neighborhood -- or a compact, mixed-use rail-connected suburb such as Evanston or Oak Park -- a household would expect to see their auto-generated C02 drop steeply toward about 2.5 tons per year. They'd be switching to transit for some trips, which involves some generation of greenhouse gases, but at a far, far reduced rate. And more destinations would be within walking and biking distance too. Take a closer look at the maps.
The difference is all in the efficiency with which people move around highly urbanized environments. Thanks to the Center for Neighborhood Technology, the original source of this revealing map.
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