Do you have a source for this claim?
If you are implying that urban centers are expanding (suburbs, exurbs etc) and swallowing up formerly rural areas, then I could maybe see that being true. However, I live in a rural area and our population has remained the same for 15+ years. That's another thing in of itself (our population isn't increasing, it's staying the same) but there isn't a flight out of town or anything.