Immigration 'issues' don't raise the populations. It's just movements of people.
https://www.learner.org/courses/envsci/unit/text.php?unit=5&secNum=4
Many people interpret forecasts like this to mean that population growth is out of control. In fact, as noted above, world population growth...
China enforced the one-child policy which resulted in baby girls being abandoned to orphanages, as rural Chinese preferred boys to work for the family.
They also got fined if a second baby was born, which resulted in rich people having two children, whilst poor people were made poorer by the fine.