[centimeter]

The net direction of subsidy from rural to suburban to urban is complex to calculate and subject to dispute.

For example, urban centers are net importers (of food, processed goods, building materials, etc.), and benefit disproportionately from heavy freight on roads.

An example of a serious but less obvious negative externality imposed by urban centers is the bulk import of population, since urban centers always reproduce below replacement rate. The urban centers basically take most of the intelligent people from non-urban areas and then ensure they don't reproduce.

[lotsofpulp]

More road space means people living further from one another. People living further from one another means exponentially more energy consumed to move mass further distances. Hence roads cause a huge externality of pollution.

[centimeter]

That's not what exponential means.

Cities also rely on roads, just in a different way; they require road networks to bring them food and manufactured goods, transported at greater distances than similar products in rural areas.

[lotsofpulp]

You need less road space to distribute resources to more people in dense areas. For example, the resources to deliver everything people need in Manhattan is less than if you took all those people out of Manhattan and spread them around in detached houses.

By exponential, I meant when you increase the distance between them, you multiply everything consumed by an extra factor. More pipe for water and sewer and gas, more wire for electricity, more road for more intersections and wider roads, more miles driven for garbage trucks, more schools, it has a knock on effect of all consumption.

And it’s just as simple as that - the more you consume, the more you pollute. The more you consume space, the more you consume everything since the further everything has to get pushed (assuming you’re still expecting all the trappings of modern life). I am guessing that the extra space I am consuming now is probably a luxury that future generations won’t have, assuming population levels of people who live an American lifestyle hold steady or rise.

[natmaka]

"Expecting all the trappings of modern life" is key.

Isn't it mainly tied to "density"? All other parameters being equal consuming only local resources at a rate which doesn't extinguish them solves the equation. On the pollution side of this: even if is is strictly the same (quantitatively and qualitatively) aren't natural surroundings more able to cope with it ("digest") if produced on a larger area, more sparsely, somehow diffusing the load?

We may, however, be unable or unwilling to adequately reduce our expectations.

[fredophile]

Why are these things transported further to get to cities than rural areas? I could see the argument if most of these things came from most rural areas but that largely isn't the case. Many manufactured goods are imported from other countries. Very few rural areas grow all the food they need. Instead they will specialize in a few areas, sell there surplus and buy goods from other areas. For historic reasons many large cities are located at places where these types of trade goods had to go through already to get from one rural area to another.