I mean, the thing with the environmental impacts of it is that these people already existed, so any increase in climate impact from them is driven not by actual population growth in a global sense, but in people here having a higher quality of life. We need to decouple that from carbon emissions of course, but in the meantime, I dont know that “Some people who were incredibly poor are now a bit less poor” is really the worst reason for an increase in climate impact. 100000 a month is a bit over million people a year, which sounds like a lot, but when the country has over 300 million people, that is in the ballpark of a third of a percent. That doesnt seem like very much to me. It seems silly to say the country is “bursting at the seams” or “we’re full” as I sometimes hear people say in the same vein- when we have a lower average population density than the world as a whole. Countries like India and China manage well over 4 times that in a similar amount of space, and if we want to stay globally relevant in the long run in a world where there are countries with over a billion people that are rapidly developing economically, it seems to me that we would benefit from roughly similar numbers. If we can achieve this by allowing the impoverished from elsewhere to come, add the better aspects of their culture to ours like migrant groups have done before, and improve their quality of life while doing so (granted, actually treating immigrants to the standards we treat eachother is something we need to work on), that strikes me as win-win. Yes, population growth poses a strain on things like housing and public services, but we do have enough raw land, and the infrastructure is something that we can build, indeed, building it is itself something that can drive economic growth and job creation.