The cause of a refugee crisis is overpopulation of the human race. Wars, waged in overpopulated areas, cause massive shifts of people to safer oness.
It is imperative that developed countries, like the US and Europe, Russia and China refrain from bombing the crap out of the underdeveloped ones, not for the deaths that occurr, which are bad enough, but for the starving millions that are left. That is part of the cause, but not all of it.
History has seen mass movements of people ever since biblical times. We did it, to the New World , Australia, NZ etc. Now, the Asians are doing it. We can only put a brake on it, but it is going to happen, anyway.
Until we wipe ourselves out, entirely, that is.
That is my pessimistic outlook of the situation. It comes with climate change. Being elderly, I can afford to be philosophic. What about the generations to come?.
I think that they will do the same as us, that is moan , but not much else.