In places where the climate is optimal for growing food then more population can be supported in those areas, however if the climate is not suitable for this then less people will be able to live there.

It limits the number of people living in the Sshara for instance, to where they can find water.

nearby ocean beaches highest density population concentrated in most ocean neighboring countries.

See the map, people live mainly where it is warm with lots of water.

http://ts2.mm.bing.net/th?id=H.470266400...