Subject: How could the increase in population affect earth's speed?

I realize that there are alot of variables that could be taken into 
consideration to answer this question.
With the number of people on earth increasing at a fast rate, how does/can this 
affect the speed of the rotation on its axis or its rotation around the sun?  
With more people comes more buildings, but less forest.  If I understand 
correctly, damming rivers to provide electricity for the growing population can 
affect the earths rotation (Yangtze River).  
I could think of more "ifs, ands or buts", but I will leave this a little open-
ended.
Thank you.

Re: How could the increase in population affect earth's speed?