"The point is that nations with higher average GDP are far more able to utilize land efficiently (that is, need less land, for example to provide food for a given person)."

So if the richer nations are more efficient, then why do they also have a bigger footprint? Shouldn't China be considered more efficient since it supports a billion people with the same size footprint as the US?

We are comparing apples to oranges here. I've already said, GDP measures something totally different than ecological footprinting. There are resources and then there are resources. Ecological footprinting measures natural resources - air, land, water, lumber, food. Ecological footprinting does not measure the value of services, government spending, capital investments, ideas, entertainment, etcetera.

Now I'm not saying that technology can't aid in more efficient utilization of natural resources and thus give us a smaller footprint. I'm just saying that it hasn't.