The earth is very finally balanced ..With all this mass movement of people the earth is becoming unstable
Imagine being on a boat and the weight moves to one side and not evenly distributed the boat becomes unstable and acts in an unmanageable way
The boat is in the water sailing about normal once the boat has worked out its weight distribution
The earth has worked out its weigt distribution over millions of years and nature has put the number of humans that it needs in certain countries . You can't start morning great sights of people where you want or you unhinge the way the earth and the finally tuned nation stability . It's nature that tells us where certain people and certain animals and birds live not sir David Attenborough on BBC 2