I usually say if every human being on the planet were placed in Texas, it would be less dense than Paris as an argument against an area being "too crowded", but this is an even more jarring comparison.
Take food production into account and the planet looks a little more crowded.
All that biomass packed into one place would make a great energy source, although it'd be mostly anaerobic decomposition unless you were close to the surface. We wouldn't have to burn fossil fuels any more with the amount of energy it'd produce for all the humans... oh... wait... I think I've found a problem.
If every human being on the planet was in Texas, Paris would have 0 people per square kilometer