introducing mass migration and the result was the fall of the West Roman Empire and the decline everywhere.
That's only one theory, regarding why the Western Empire collapsed. It's not even the most popular one.
The Eastern Empire continued to receive huge amounts of people, especially from the Slavic world, and somehow managed to last until the 1450s.
I would argue demographic collapse poses a much larger threat, than immigration ever could. In East Asia, in the early 1990s, there were ten working age people for every retiree. By 2060, this proportion is set to change to a 1:1. The World Bank and IMF, project that productivity growth has to be double of what it is right now - for countries like Japan and Germany to maintain their current living standards.
Who's gonna care about immigrants, when a grandson hates his grandpa's guts for the mere fact of existing? Any fellow young person from Nigeria or Syria, will be an ally in relieving the burden that old farts generate on the system.
In Britain, already, no white person wants to take care of his stinky and bedridden parents or grandparents. Instead, nurses from Jamaica and Pakistan take care of all the old white people nobody cares about. Imagine how the picture will look when there are as many, or even more, old people as there are young people?
Only one thing can save us all from this impending collapse, and that's the rise of some superintelligence which will make work unnecessary for the overwhelming majority of people, while simultaneously resolving resource scarcity.
If AI takes care of all the work, maybe we can learn to live in a world of old farts. However, if people will still actually have to work, and pay taxes into large welfare systems that support non-working people - then we are well and truly F*CKED.
So I'm pro-immigration, because numbers give power, numbers generate wealth, numbers provide vitality.
Russia - my home country - has too small a population for its size. Instead of 150 million people, we should have at least 400 million. But because Russians refuse to start families, and refuse to have babies, the only way we're gonna get there is opening the gates to Central Asia, Africa, and the Subcontinent.