How do those small urban footprints survive though? They bring in outside resources, external zing the impact elsewhere and adding in the cost of transporting goods into and waste out of the urban centers.
There isn't a magic answer to it, but simply saying dense areas use less footprint for shelter ignores all the other necessities and conveniences consumed by the people living there.
5 single-family homes will consume the same amount of food and water as 5 units in a few duplexes or a five-over-one. The SFHs will consume more energy for heating and cooling (related to larger footprints) and use more resources to send power and water (larger distances to send power and water.) An SFH consumes more resources than a multifamily-housing unit holding the same number of people.
That really does entirely depend on the size and style of the SFH, location on the land, lifestyle, etc.
Single family homes are often easier to power off-grid with solar if that's on the table, though again with regards to externalities the solar power equipment likely sends those costs to multiple countries on the other side of the planet.
They would still use more energy in total, since flats insulate themselves to a certain extent due to having less outside walls & tend to be smaller requiring less energy to heat the space. You can also power flats with renewable energy. At this point less total energy is good regardless.
Suburbs also bring in outside resources. The difference is that distributing those resources and collecting waste within the city is less costly than distributing resources and collecting waste within the suburb.
Spread-out suburbs require more heating, transportation infrastructure, and more physical land to exist than alternatives. You can argue for them based on other gactors, but they use more resources, full stop.
Spread out rural housing does not mean less transport to bring in outside resources, but vastly more because most goods are still "outside resources" even if you literally live on a farm, and most people don't.
Yes but the sewage from a block of flats takes less transportation for the equivalent amount of people living in suburbs with thousands of square m for a single house
There isn't a magic answer to it, but simply saying dense areas use less footprint for shelter ignores all the other necessities and conveniences consumed by the people living there.