Slicing the data on cities reveals fascinating patterns.
Trend watch! Supercities will be all the rage in the 21st century, as fully 2/3 of the world's population concentrates in urban regions. This centuries-long migration represents the culmination of a process of industrialization stretching back to the early 1800s, with all of its attendant social and environmental consequences.
I've got a handful of links that take a data-driven driven look at cities. First up, what do large cities and elephants have in common? Both appear to be organized according to underlying mathematical principles that make them more efficient than their smaller cousins. On a pound-for-pound basis, an elephant uses less resources than a mouse. To be precise:
The relevant law of metabolism, called Kleiber's law, states that the metabolic needs of a mammal grow in proportion to its body weight raised to the 0.74 power.
Cities behave much the same way:
For instance, if one city is 10 times as populous as another one, does it need 10 times as many gas stations? No. Bigger cities have more gas stations than smaller ones (of course), but not nearly in direct proportion to their size. The number of gas stations grows only in proportion to the 0.77 power of population.
The gas station example is a trivial application of what appears to be a deep relationship. Cities, with their branching patterns of pipes, sewers, streets, and wires, appear to become more efficient in size in just the same way living organisms do, which is one of the reasons that increasing urbanization is on balance good for the planet.
Not that we should take the greater efficiency of cities for granted. Humans control their built environments in ways that have dramatic consequences. In a simple but revealing demonstration of the different forms cities can take, Neil Freeman has traced a series of subways systems, all to the same scale. Here's Tokyo juxtaposed with the San Francisco bay area:
Check out the entire series. How does your city compare?
This piece originally appeared in The Terrapass Footprint.
Photo credit: Flickr/tanakawho, Creative Commons License.
Quite possibly all very true, but there is no mention of the downside.
For instance, all this crowding together of people leads to a whole welter of health problems. Some of these are treated using pharmaceutical drugs, whose long term (over generations) benefits are yet-to-be-proved.
Others are swept under the carpet. Stress and depression, leading to violence and social breakdown.
"Oh that's just life" many say. Over the next century or so, it could be a greater threat to human life than climate change.
Chris, that soiund like a reversal of cause and effect - cities cause mental health issues becuase they often unpleasant places to live, but the whole point is that they don't have to be. Personally I get stressed when away from the city, and I love what living in a city allows. (Obviously, even my beloved town has a lot that needs improving, but I prefer it to living somewhere smaller.)
True - density does equal efficiency in most cases. But we can't ignore the very human desire that led to the development of the suburbs in the first place: People like having some space to themselves! Having a backyard with a patio and a garden is 'the dream' for a lot of people, myself included. Studies have shown that for many people, being in a busy, loud, contemporary urban environment tends to be a very stressful experience (no surprise!).
If we're going to get enough people to make the transition to a more efficient, urban lifestyle, we need to make sure that "urban" doesn't mean over-crowded, loud, fast-paced, etc. Clearly, everyone in a dense neighborhood can't have a big, grassy yard of their own. But cities need to be designed to appeal to the basic human desire for open space, plants, peace and quiet. Otherwise, the megacities of the future will continue to be a place people get "stuck" when they're not wealthy enough to escape to their dream home in the country.
There is no cost incentive to get the majority of humanity to live in a big city. You pay more and get less. Across the board.
Until that is changed, it is merely a pipe dream.
I wish I could see more hard data on the efficiency of high density cities. Studies show that government expenditures are lower per capita in lower density areas. Doesn't that completely contradict your claim that dense cities are more efficient?
AW -- whatever the nature of the incentives, most people very clearly prefer to live in cities. In 1800, 3% of the world's population lived in urban areas. By the end of this century, that number will be closer to 66%. By the way, "urban areas" doesn't mean downtown Manhattan. There is a lot of diversity to cities.
randplaty -- there is plenty of research showing cities emit less emissions per capita than more rural or suburban areas. See for example:
I'm referring specifically to energy efficiency. Government spending doesn't seem related to efficiency in any obvious way. In fact, government spending could easily promote efficiency. For example, building a subway system can lower living costs for citizens while also reducing energy use.
I live in São Paulo and I think that this debate is very intersting. From what I'm aware the big cities create a lot of problems to the body and mental health of al the living beans. Here in São Paulo for example, we have a LOT of cars that create a loudy noise, polution and a terible traffic. This problem is caused by governamental policy that benifits the automobile idustry since 1950's.
This was one of the biggest mistakes because today almost all of the transportation of the production is made by road, this creates an enviromental and logistic problem. Here, we have one of the biggest transportations problem, because our public transportations is a bus system, and the subway lines are very little.
Since that, everyone wants to have a car or motocycle to locomote themselfs, so the sales of car are up to 500-800 cars soled per day, just in the city. The average of car per habitant is 1-2, what gives an average of 6,2 milion cars in the streets every single day.
Well, from what I see, one day this city is going to stop in time because there is so much traffic that the only solution will be to ride bikes.
I hope this day comes.
There are alternatives between megacities and smaller cities or independent areas within the Cities. I live in NYC and am very interested in urban agriculture and rooftop gardens. Clearly there is more scope for urban agriculture where houses are not so close together and people have space to grow things on the ground as well as up high. From world-wide census materials, smaller cities appear to be growing even faster than mega-cities and I think this is because they offer more options for quality of life along with urban advantages.
I should email u about it.