Migration can effect us in many ways like lack of resources and eminities , lack of jobs etc
When someone migrated to a city the population of the city has to partake some of it's resources to help the person sustain. Migration on a large scale can give rise to various problems as resources are limited but more and more people depend on them. Thus , the natives of the city will slowly become alienated as they won't have jobs,water. overcrowded localities along with dreaded traffic, pollution will make them suffer. So, migration only to a certain extent is permissible