I respect your opinion but its not always about habitat , many country even lived beside polluted river , just to get a waste food so their family can eat, Too many children in a family is a crucial things to them, first the children can't go to school because of poverty, second the they don't have a house and if theyre going to relocate , it I's much harder to them to adopt where they will be placed.
Poverty is a completely different question. Of course, I realize that poverty has a big effect on birth rates. The poorer people are, the more they typically tend to have children. They need the children to work for them by selling something or working on the farm to get more money for the family. Birth rates go down as populations get more wealthy. The nice thing about rivers is that they move. To stop pollution in a river, you need to stop polluting it upstream. Typically, the more wealthy a country gets, the better they get at dealing with pollution. (I'm not sure about China, but it seems like they're at least making some efforts now.)