M.I.T. Technology Review wrote that creating denser cities doesn’t reduce C02 emissions enough to make a major difference by 2050, when some of worst effects of climate change are expected to take effect. A recent report from the National Academy of Sciences (NAS) found that policies designed to make cities more compact will “do little to reduce gas consumption by 2050.” Fighting urban sprawl, and the time spent commuting via cars, has been viewed as critical to reducing C02 emissions. Currently, most commuters in the U.S. have no transportation alternatives and must drive long distances for work.
Instead, improving CAFE standards, developing renewable vehicle fuels, and increasing the energy efficiency of vehicles may have a much greater impact on car-related CO2 emissions. ”An immediate 0.1 percent reduction in the weight of all vehicles nationwide would be 10 times more effective at reducing greenhouse gas emissions than an immediate 0.1 percent increase in housing density nationwide,” notes a supplemental report to the NAS study.
On the ability of reduced sprawl to lower U.S. C02 emissions, the NAS writes: “Increasing population and employment density in metropolitan areas could reduce vehicle travel, energy use, and CO2 emissions from less than 1 percent up to 11 percent by 2050 compared to a base case for household vehicle usage, says a new congressionally mandated report from the National Research Council, although committee members disagreed about the plausibility of achieving the higher estimate.”
M.I.T. Technology Review argues that considering the scale of the undertaking, relatively limited C02 emission reductions would result from a massive U.S.-wide effort to make cities and communities more compact. “Even if 75 percent of all new and replacement housing in America were built at twice the density of current new developments, and those living in the newly constructed housing drove 25 percent less as a result, CO2 emissions from personal travel would decline nationwide by only 8 to 11 percent by 2050, according to the study. If just 25 percent of housing units were developed at such densities and residents drove only 12 percent less as a result, CO2 emissions would be reduced by less than 2 percent by 2050.”
With the exception of Portland, Oregon, to date, creating denser cities hasn’t successfully reduced car-related C02 emissions, writes M.I.T. Technology Review. “An exception to the nationwide trend of sprawling suburban homes is Portland, OR, where residents drive 17 percent fewer miles per day than the national average because of boundaries set on urban growth and a light rail system that both got their start in the mid-1970s.” Anthony Downs, Brookings Institution, added: “Portland is only one out of 350 metropolitan centers in the country that has strong transportation and housing policies directed at increasing population density. It’s not exactly a groundswell movement.”
While there are clearly many other environmental, economic, and social benefits to increased density (including more efficient land use, less pollution, economic diversification, improved downtowns, reduced commute times), M.I.T. Technology Review says a greater C02 emission reduction would result from a ”focus on fuel-efficiency improvements to vehicles, investments in renewable energy, and cap and trade legislation now being voted on in Congress.”
Read the article and the NAS study
Image credit: Wikipedia, NYC Skyline
Of course it will take a combination of strategies to solve our problems. That much is common sense.
That having been said, this MIT report is more full of holes than Swiss cheese. For one, the authors don’t seem to understand that the “cities not sprawl” strategy reduces car trips by other means in addition to just higher densities.
Using this report to say “look, we need cleaner sources of energy too” is fine. Using it to say “we shouldn’t bother densifying because that’s not the answer” would be deeply flawed.
This report has been uniformly discredited by all informed sources. It is unfortunate that the ASLA is party to the spread of this thinnly disguised sprawl-promoting propaganda.
Why does this study only propose densities at twice as dense as they are now? That would be every single family house being converted into a duplex. I’m sure cities can increase their density by 8 to 20 times what the current density is. This study is flawed if we are only assuming a duplex as the next logical step from a single family home.
Even if the study is methodologically sound, why would we urbanize new areas in a way that we know is resource intensive? And why would we not want to put in place an urban pattern for whole regions that further reduces GHG during a later phase?
That said, criticizing land use strategies as ineffective because it is “not exactly a groundswell movement” only idenifies achallenge not an eventuality. Professionals are overcoming in real ways. Transit-oriented development was not even in our lexicon twenty years ago. We now have regional plans for many metro areas awaiting implementation, but need government to stop shift huge subsidies for auto-centric infrastructure toward new priorities, and to adopt codes and policies that promote walkable transit-oriented places.