The ecological footprint is a well-established way of unifying critique of overconsumption and overpopulation. Individually one's personal footprint is "the number of Earths required to support everyone living just like you". Civically it is the size of the land base that is required to support any one city. Fans of turn-based strategy games are usually quite familiar with the way that a city takes up space on the land, and city management to minimize this footprint often matters.
The philosophy of ecological footprints however has a God's Eye View problem: the assessment of the individual footprint is from a very abstract position that allows one to compare lifestyles across ecoregions. It is literally Kant's categorical imperative, to do nothing oneself that if done by everyone would be immoral.
For this reason, the civic definition that defines a city footprint on the land just surrounding it, may be preferable, as it does not assume any planet-wide view, but is more situated report of how THESE surroundings support THIS city.
See w:ecological footprint for the Sysop Vandal point of view.